VATIS Update Waste Management . Sep-Oct 2007

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Waste Management Sep-Oct 2007

ISSN: 0971-5665

VATIS Update Waste Management is published 4 times a year to keep the readers up to date of most of the relevant and latest technological developments and events in the field of Waste Management. The Update is tailored to policy-makers, industries and technology transfer intermediaries.

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Indian firms continue importing hazardous waste

As if Indias trouble in handling its own hazardous waste is not enough, private firms illegally imported Rs 2,600 million (US$65 million) worth of such waste in 2006-07. In 2005-06, hazardous waste valued at US$ 67.5 million was imported by private firms. The Supreme Court Monitoring Committee, which reported this, also disclosed data on 141 illegal sites where hazardous wastes are dumped in 13 states. The Committee noted that these data may be only the tip of the iceberg, since the government doesnt completely track either the import or the dumping of dangerous waste.

Adding to approximately 4.8 million tonnes of hazardous waste generated by 29,500 Indian factories, the report lists tonnes of clinical waste, ash from incineration of waste, scrap of pet plastic bottles, mercury, lead, arsenic and organo-mercury compounds being imported into India in spite of these being banned under the law as well as under the Basel Convention. In 2006-07, India ended up importing 9.92 million tonnes of plastic bottle scrap and mercury worth US$2.85 million.

The Committee noted that clinical waste and incineration ash from municipal waste were also being imported. It reported that no inventory is maintained of the quantity of legal and unauthorized hazardous waste that has been imported into the country. The imports come in violation of not only the regulations, but also the 2003 Supreme Court directives. Despite a long running battle on the issue and several directives and orders from the apex court the situation remains grim.


Sri Lanka launches a plastic waste management project

The Central Environmental Authority (CEA) of the Sri Lankan Ministry of Environment and Natural Resources has started a project to manage the countrys plastic waste. The Plastic Solidarity Committee comprising the operators of the plastic industry will assist CEA to conduct the programme, which is funded by the cess levied from the plastic raw material imports.

The Director of the National Post-Use Plastic Management Project, Mr. M. Rizvi Majeed, said that the country has a few recycling factories of plastic waste but they dont operate totally as the return of plastic waste is only 10 per cent of the need. The new project, which will be launched in some selected dis- tricts initially, will encourage sorting out the plastic waste and recycling them.


China to set up centres to handle e-waste

China will set up three centres to combat electronic pollution, said the countrys Ministry of Information Technology (MIT). The three centres, all under electronics research institutes supervised by MIT, will be responsible for testing electronic products, as well as conducting research on standards, energy saving, product recycling and disposal. Mobile phones, for example, contain heavy metals such as beryllium and lead, as well as bromide used as a flame retardant, all of which are hazardous for humans. The cadmium contained in a single mobile phone battery can contaminate almost 60,000 litres of water.

The new centres will implement the governments Management Methods for Controlling Pollution by Electronic Information Products. Chinas first green regulations in the electronic sector, which took effect on 1 March this year, are intended to enhance environmental protection by reducing or eliminating certain toxic and hazardous substances in electronic products. China is expected to issue a new regulation in August requiring companies to guarantee that toxic substances will not leak from their devices. The nation will introduce standards on non-lead soldering at the end of the year.


Malaysia passes solid waste bill

In Malaysia, the Solid Waste and Public Cleansing Management Bill 2007 was passed, paving the way for an improvement in solid waste collection and management by the concession holders. Housing and Local Government Minister Datuk Seri Ong Ka Ting said the local authorities and concessionaires would have to adhere to the Key Performance Index status, requiring them to improve services or face action. 

The Solid Waste Management Corporation would implement policies, besides acting as a watchdog on solid waste management and enforcement, Datuk Ong said. Its role will go together with the National Solid Waste Management Department, as the regulatory body placed directly under the ministry.  

The corporations director general, the Minister said, will have control over the local authorities, which in turn will act on his behalf in enforcing solid waste management, cleanliness laws, taking action against concessionaires which do not fulfil their responsibilities, or those who destroy the environment such as being involved in illegal dumping activities. 


Japan to help upgrade Sri Lankan waste management

The Japanese government through its Japan International Cooperation Agency (JICA) has commenced a 4-year technical cooperation project this March to upgrade the capacity of Sri Lankas newly established National Solid Waste Management Support Centre (NSWMSC) of the Ministry of Local Government and Provincial Councils. An overall goal of the project is to improve the solid waste management of local authorities. With technical support from JICA, the NSWMSC is expected to provide guidance to local authorities in preparing solid waste management plans, and to obtain grant and loans from financial institutions to implement the plans.

Under this project, JICA dispatches experts and provides equipment and training opportunities for Sri Lankan counterparts. JICA will transfer the technology to the NSWMSC staff to enable them to assist local authorities to draw solid waste management plans in cooperation with authorities and provincial councils in accordance with the Solid Waste Management National Strategy.


The Philippines to ask oil companies to pay for spills

The Government of the Philippines has introduced a law that requires all major companies that ship oil using the island nations waters to pay into a fund, which can be used to tackle future spills. The Oil Compensation Act has largely been seen as an acknowledgement of the criticism over the governments slow response to a huge spill off the coast of Guimaras last year, the worst in the countrys history. An oil tanker sank off the coast of the island last August, causing extensive damage to both the environment as well as the livelihood of local fisherfolk. The remediation took months to complete and was plagued with several problems including the sinking of a clean-up vessel, which went down carrying large amounts of contaminated sludge.

Under the new act, any company transporting 136,000 t or more of oil each year will have to contribute to the fund, which will cover the costs of containment and clean-up operations in the event of a spill. The official reasoning for this approach is that the blame game which follows a spill under the traditional polluter pays principle could cost valuable time and lead to a delayed reaction in tackling the problem.


Chinas paper recycling industry protects forests

Chinas booming recycling industry is helping to slow the destruction of forests worldwide, providing a strong market for wastepaper that mostly comes from Europe and the United States, according to a recent study. Almost 60 per cent of the fibre employed to produce paper and paper board products in China is derived from wastepaper, the report found. In the last decade, Chinas wastepaper imports increased by more than 500 per cent  from 3.1 million tonnes in 1996 to 19.6 million tonnes in 2006  with the growth mostly occurring during 2002-06.

China is by far the worlds biggest consumer of wastepaper and that is a good thing because in the last four years alone, China has prevented 65 million tonnes of wastepaper from heading to landfills in Japan, the United States and Europe, said Mr. Brian Stafford, the lead author of the report and an industry consultant. The industry includes one of the countrys richest people, Ms. Zhang Yin, the founder of the Nine Dragons Paper Co., who made a fortune by turning recycled paper from America into packaging products.


Nepal court orders a study on medical waste disposal

In Nepal, the Supreme Court has directed the Ministry of Finance to form a committee to probe whether medical waste is being properly disposed of in the Kathmandu Valley. A division bench of the court said the committee should comprise representatives of the Health Ministry, the Ministry for Environment, Science and Technology, as well as hospitals and nursing homes in the valley. The committee will have four months to complete a study and submit its report to the apex court.

The directive was in response to a public interest litigation filed by a group of lawyers of Pro Public, an NGO. The petitioners demanded that the court intervene and order authorities concerned to properly manage medical waste, which has exposed the general public to several health hazards. The petitioners have sought an order to the government to pass a separate regulation as per Clause 24 of the Environment Protection Act-1997 and fix criteria for medical waste management.



Device that recycles plastic into gas

Global Resource Corporation (GRC), a company in the United States, is taking recycling to another level by turning back plastics into the oil they were made from, and gas. GRC claims the process requires only a finely tuned microwave that uses 1,200 different frequencies within the microwave range, to act on specific hydrocarbon materials and a mix of materials made from oil to reduce the product back into oil, a fuel gas and some residues.

As the material is microwaved at the appropriate wavelength, part of the hydrocarbons that make up the plastic and rubber in the material are broken down into diesel oil and combustible gas. GRCs machine is called the Hawk-10. Its smaller incarnations look just like an industrial microwave with bits of machinery attached to it. Larger versions resemble a concrete mixer.

Running 9.1 kg of ground-up tyres through the Hawk-10 produces 4.54 litres of diesel oil, 1.42 cubic metres of combustible gas, 1 kg of steel and 3.40 kg of carbon black, said Mr. Jerry Meddick, GRCs Business Development Director.

Contact: Mr. Frank Pringle, President, Global Resource Corporation, Bloomfield Business Park, 408 Bloomfield Dr. Unit 3, West Berlin, NJ 08091, United States of America. Tel: +1 (856) 767 5661



Separation of multi-component polymeric materials

Kimberly-Clark Worldwide Inc., the United States, has patented a new method of separating one or more polymers from a waste stream of mixed polymers. The method includes adjusting the temperature of the mixture, either by heating or cooling, to bring the temperature to a point at which unravelling of the polymer mixture occurs. Mechanical processes, such as grinding, are also used before, during or after temperature adjustment to fracture and separate at least one polymer from the mixture.

The prescribed temperature range may be determined, for example, by differences in the glass transition temperature between polymeric components and / or the temperature at which adhesion is lost between various components. Separation of a polymeric component is possible using conventional separation techniques by fracturing that component to the extent that its size and / or geometry is altered, or by causing delamination or any loss of adhesion between the components, based on differences in their physical properties or geometries. For instance, the polymeric component with the higher glass transition temperature can be ground to powder form while the polymeric component with the lower glass transition temperature remains fibrous even when ground. Thus the polymer can be separated from the remainder of the waste stream using screening, fluidized beds or any other suitable separation technique, which separates particles by size, geometry or by leveraging physical property differences.

The invention is particularly suitable for separating mixed polymer waste streams from such processes as stretch-bond laminating processes and vertical filament laminating processes, and from waste streams resulting from the manufacture of a variety of materials, such as non-woven fabric made with multiple component polymeric strands. The method can separate polypropylene, polyethylene, and / or linear low-density polyethylene, for example, from such waste streams.


A possible way to recycle Nylon-6

Nylon-6 an artificial polymer used in carpets, clothing and car parts is made by chemically linking large numbers of molecules derived from a petroleum product called caprolactam. Current processes to break apart (depolymerize) Nylon-6 typically need high temperatures and high pressures. The processes are also relatively inefficient, says Mr. Akio Kamimura, an organic chemist at the Yamaguchi University in Ube, Japan. Incinerating the polymers in mixed trash can create prodigious amounts of toxic compounds. Therefore, Nylon-6 normally ends up in landfills.

Mr. Kamimura and his colleague Mr. Shigehiro Yamamoto have developed a bench-scale process that depolymerizes Nylon-6 and regenerates caprolactam. The chemists placed chips of Nylon-6 and small quanti-ties of a catalyst in various ionic liquids (consisting solely of positively and negatively charged ions). At 270C, the depolymerization reaction was inefficient, and the team could recover only 7 per cent of the caprolactam contained in the chips. At temperatures above 330C, the reaction was more efficient, but only 55 per cent of the caprolactam was recovered, as some of the substance decomposed in the heat.

At the intermediate temperature of 300C the caprolactam yield neared 86 per cent, says Mr. Kamimura. More importantly, at that temperature the ionic liquid did not become tainted with reaction by-products. The researchers were able to reuse their ionic liquid five times without notable drops in caprolactam yield.


Method for recycling articles based on vinyl polymer

Solvay S.A., Belgium, has secured a United States patent on a process for recycling an article based on at least one vinyl chloride / vinylidene chloride polymer. The process essentially has the following steps:
  • The article is reduced to fragments with a mean size of 2 cm to 30 cm;
  • The fragments are placed in a rotary drum and brought into contact with an azeotropic or quasi-azeotropic mixture of water and a solvent (methyl ethyl ketone, methyl isobutyl ketone or tetrahydrofuran) capable of dissolving the polymer, at a temperature of at least 120C and a pressure of 4-10 bar;
  • The polymer dissolved in the solvent is precipitated by a reduction in pressure and by injection of steam into the solution obtained, which also results in the entrainment of the solvent-water azeotrope and thus leaves a mixture that is essentially composed of water and solid polymer particles; and
  • The polymer particles are collected through filtration, and the liquid fraction is recycled.


Plastics waste recycling machines

Energy Co. Ltd., Japan, offers a 3-in-1 machine for recycling plastics waste. The machine combines in one unit a shredder, an extruder and a pelletizer. It comes in four models differing in processing capacities. The machine can process wastes of HDPE, LDPE, PP, PS, ABS and EVA. The output capacity ranges from 380 kg to 700 kg.

The shredder has a 2 hp conveyor of size 3,500 mm length and 650 mm width. It has 12 rotary cutters and 16 stationary cutters. The extruder has an L/D ratio of 32:1 and is powered by motors of 125 hp to 200 hp.

Contact: Energy Co. Ltd., Sky-Building 5b, 6-89-1 Onoecho Naka-Ku, Yokohama, Kanagawa, Japan 231-0015. Tel: +81 (45) 640 0025; Fax: +81 (45) 641 7884.


Shredder for bulky plastic containers

WEIMA America, the United States, has developed a new version of the WLK 12 single-shaft shredder for the size reduction of bulky plastic containers and parts with thin walls like totes, barrels, drums, tanks, etc. The machine has a compact design and includes a new press-down device that enables the customer to shred even the largest size totes without the need to pre-cut.

Whole pieces are directly loaded into the front of the machine. In the cutting chamber, the press-down device pushes the material down, and the horizontal ram pushes the material into the rotor. Both pressing actions are controlled by sophisticated electronic controls that optimize the pressure applied to the rotor. The shredded material is will pass through the screen (20-100 mm) mounted under the rotor.

The machine can handle intermediate bulk containers and other large totes along with materials in sizes up to 1 m x 1 m x 1 m. WLK 12 is equipped with a 50 hp / 60 hp motor to achieve capacities of 600-1,000 kg/hour.

Contact: WEIMA America Inc., 3678 Centre Circle, Fort Mill, South Carolina, SC 29715, United States of America. Tel: +1 +1 (803) 802 7170; Fax: +1 (803) 802 7098



Scrap tyre recycling system

T. C. Chang Trading Co., Taiwan, offers a machine for recycling scrap tyres. The machine has a processing capacity of 800-2,000 kg/h of tyres, depending on the tyre type, with a maximum size of 1,200 mm x 385 mm). It produces crumb rubber of size below 6 mm. The weight of nylon that remains in the crumb rubber is about 0.2 per cent for steel truck tyres and 0.5 per cent for car tyres. The machine outputs 150 to 500 kg/h of steel wire, and 20 to 500 kg/h of nylon and other materials.

Contact: T. C. Chang Trading Co. Ltd., No. 5-1, Lane 44, I-Sou Street, Taipei City, Taiwan, TW 104. Tel: +886 (2) 2591 1133; Fax: +886 (2) 2593 1166.



Three-phase autoclave process

The VariClave three-phase process was developed by OnSite Sterilization LLC, the United States, to address multiple issues related to autoclave processing of regulated medical waste. In the first phase, steam is introduced into the chamber by gravity, displacing the air in the chamber and pre-heating the stainless steel shell and waste load. The steam pressure in the vessel is then increased to a minimum of 15 psig and temperature to 121C, and this condition is maintained for a period sufficient to kill any airborne pathogens (ABPs) that may be present. Finally, a vacuum is drawn on the vessel to remove any tramp air and prepare for Phase 2. The cycle is repeated twice for the red bag & sharps cycle and thrice for the red bag & suction canister cycle.

Phase 2 begins with the processing chamber under vacuum, into which steam is introduced, filling the chamber and interstitial spaces in the waste. Steam pressure and temperature are maintained at a minimum of 15 psig and 121C, respectively, for a period sufficient to heat and hold the waste for sterilization. The chamber pressure being vented to atmosphere signals the end of Phase 2. Phase 3 has been included as part of the cycle to prepare the bins and material to be safely removed from the chamber. It begins with the operation of the vacuum pump, which removes residual moisture from the chamber and the waste. After relieving the vacuum, fresh water is sprayed on the sides of the bins to cool them for safe removal. The cycle ends with a final operation of the vacuum pump to reset the door seal and remove any remaining moisture.

Contact: OnSite Sterilization LLC, 319 Commerce Court, Suite 103, Pottstown, PA 19464-3478, United States of America. Tel: +1 (610) 495 8214; Fax: +1 (610) 495 8215



Sterilizer for hospital waste

Panama Equipment Services, Pa-nama, offers an infectious waste processor for medical waste, pathological and infectious liquid wastes, and classified food waste, such as that from airplanes and ships. The machine is available in many sizes, models and configurations, all equipped with fully automatic controls and achieve 610 sterility with steam. The main features include:
  • There is no need for special autoclave bags, or pre-treatment of the waste.
  • No need for pre-shredding of infectious waste, as the fragmentation occurs inside the sealed vessel.
  • Liquids and gases remain locked inside the vessel until sterilization is complete nothing is vacuumed or pumped out in its infected state.
  • Waste is completely dehydrate the waste, regardless of its original water content.
  • All the hot condensate from the jacket is recycled, offering economical operation.
  • High level of sterilization owing to continuous agitation, not just disinfection.
  • No harmful emissions at normal operating temperature (121C).

Contact: Mr. Edilberto Rodriguez, Panama Equipment Services, Urb. Chanis, Calle 110-a, 364, Panama 6618-2163, Panama. Tel: +507 (224) 8779; Fax: +507 (224) 8779.


Medical waste reduction system

The Medical Waste Processor base model MD-1000, from Environmental Waste International Inc. in the United States, can treat 1,225 kg of biomedical waste per day. It consists of three main fully integrated process steps that are managed by smart feedback diagnostic control software. The output is landfill-ready, sterilized carbon residue. Units can be also be designed to handle larger volumes. Mass and volume reduction of waste to landfill is approximately 80 per cent.

Mixed medical waste is loaded without pre-processing on to the loading/ purge chamber, which is then sealed with an air lock shutter. The waste is automatically weighed and the oxygen is purged from the chamber with nitrogen gas. Nitrogen is generated on-site by a pressure swing adsorption system that extracts the gas from the ambient air. Once the purging and weighing cycle is completed, the waste is transferred to the reduction chamber where microwave energy is applied to the waste.

The smart software is calibrated for the required energy output to the mass of the waste established during the weighing cycle. It detects the thresholds of process completion, such as moisture depletion, and adjusts the magnetron energy requirements. The process temperature of 150C to 250C is stabilized throughout the reduction cycle until process completion. The nitrogen atmosphere blankets the reduction chamber, thus preventing the formation of oxidation by-products such as dioxins and furans. The gases are scrubbed for acid content with a sodium hydroxide scrubber and then vented to a thermal oxidation unit for final destruction.

After reduction cycle, the sterilized and reduced waste is fed to cooling chamber. The cooled waste goes to a heavy-duty grinder that further reduces the carbon including sharps into a uniform residue. The material is then filled in waste bags for disposal as municipal waste suitable for landfill.

Contact: Environmental Waste International Inc., 283 Station Street, Ajax, Ontario, L1S 1S3, United States of America. Tel: +1 (905) 686 8689; Fax: +1 (905) 428 8730




Bio-hazard sterilizer

The medical waste sterilizers, from the Dutch company Tuttnauer Europe B.V., employ a high-vacuum steam as the sterilization agent, operating at a pressure of up to 33 psi and a temperature of up to 137 C. The sterilization cycle is relatively short because of the autoclaves unique design and construction the entire cycle does not last more than about 50 minutes. The sterilizer can be mounted on the wall or in a pit, or can be built into a system or be free-standing. It is designed to dispose of infectious waste in an efficient, safe, environment-friendly and cost-effective manner, as per international standards.

The pressure vessel and jacket are constructed of heavy-duty stainless steel. The loading equipment is ergonomically designed for simple, safe and easy to use. The sterilizer control system uses a state-of-the-art microcomputer, guaranteeing high reliability and safe operation. The main phases and the machines actual parameters are displayed on the LCD panel during the process.

The high-vacuum method, achieved by evacuating the air with a vacuum pump combined with steam pulsing, substantially shortens the sterilization cycle. A 0.2 m HEPA filter is used to filter the air, which equalizes the vessel pressure. The residue, which is substantially less then the original volume, is sterile and may be discarded as municipal waste. The sterilizer system is available in a wide range of capacities starting from 25 litres.

Contact: Tuttnauer Europe B.V., Paardeweide 36, 4824 EH Breda, the Netherlands. Tel: +31 (76) 542 3510; Fax: +31 (76) 542 3540



Non-burn medical waste treatment

The 12-5 medical waste treatment systems, from the United Kingdoms 3Ts International Ltd., use proven technology that shreds, sterilizes and deodorize waste. The integrated and high-performance process needs only water, bleach and electricity. The 12-5 range offers eight different models in three types economy, stationary and mobile. The process is controlled by an intuitive touch-screen interface to simplify routine operator tasks, minimize manual processes and ensure safe operation around the clock, while requiring minimal technical skills.

The treatment is carried out in four stages. In the first stage, the waste (red bag waste need not be separated) is loaded into the system via cart-dump or conveyor belt. In the next stage, the waste is broken down into particulate debris by a high-performance grinder/shredder. Waste is rendered unrecognizable and volume is reduced up to 90 per cent. In the third stage, the waste is sprayed with sodium hypochlorite/water solution and moved by a screw conveyor into a rotating kill tank. Once thoroughly mixed with the solution, the waste undergoes a pressurization cycle, and is then sterilized and deodorized. In the last stage, the tank rotation reverses and treated waste moves via a conveyor belt into a compactor or standard dumpster.

Contact: 3Ts International Ltd., Unit 1 Oak House, Aylburton Business Centre, Stockwell Lane, Near Lydney, Gloucestershire GL15 6ST, United Kingdom.


Infectious waste treatment system

Lofta Hammer Holdings Ltd. in the United States has secured a patent on a system for treating infectious waste. The system includes an impactor coupled to a mixing drum that can be pressurized, an injector, a treatment fluid containing a substance that kills pathogenic organisms, and an air pump.

The impactor pulverizes the infectious waste by impact, after which the treatment fluid is injected into the infectious waste. In the mixing drum the pulverized waste and the treatment fluid get thoroughly mixed. The mixture is then held at a super-atmospheric pressure, using the air pump which surcharges air into the pressurizable drum. Under pressure within the drum, the treatment fluid is better absorbed by the pulverized waste. After treatment, the waste is moist and pulverized to a point where it is unrecognizable. After treatment, all the pathogenic organisms in the waste are killed, and the waste can then be disposed of as ordinary waste.



Dioxin removal systems for waste gases

AGC Engineering Co. of Japan has developed a dioxin removal system based on activated carbon. The process basically involves injecting 0.1-0.2 g/Nm3 activated carbon relative to the amount of waste gas. AGC Engineering says that the system guarantees a toxicity equivalent of 0.5 ng/Nm3 or less at inlet of the bag filter, and less than 0.1 ng/Nm3 after bag filter process with catalyst device. The system can be designed to use activated carbon mixed with slaked lime, if needed. The catalyst employed is plate-type, with opening widths of 4 mm or 6 mm.

Contact: AGC Engineering Co. Ltd., WBG Marive West, 19th Floor, 6 Nakase 2-chome, Mihama-ku, Chiba-shi, Chiba 261-7119, Japan.


Catalytic removal of nitro-PAHs

Siemens Aktiengesellschaft, based in Germany, has been assigned a United States patent on a process for the catalytic removal of polycyclic aromatic nitro, nitroso and/or amino compounds (nitrated polycyclic aromatic hydrocarbons nitro-PAHs) from the exhaust gas of a combustion system, in particular a diesel engine. The exhaust gas is brought into contact with a catalytic converter at a temperature of from 150 to 600C. The nitro-PAHs are oxidized at the catalytic converter through the use of oxygen to form nitrogen oxides (NOx), carbon dioxide (CO2) and water.

The catalytic material contains, by weight, 80 to 95 per cent titanium dioxide, 2 to 10 per cent tungsten trioxide or molybdenum trioxide, and 0.05 to 5 per cent vanadium pentoxide. To oxidize the nitro-PAHs, a certain oxygen content is required in the exhaust gas. The exhaust gas of a diesel engine is inherently high in residual oxygen content.

In one of the configurations, a reducing agent containing nitrogen is added to the exhaust gas before it is brought into contact with the catalytic converter in the presence of oxygen to reduce NOx contained in the exhaust gas. In this way, first the formation of the nitro-PAHs from PAHs and NOx in the exhaust gas is prevented.

Second, the catalytic converter is used as a deNOx catalytic converter for the removal of NOx using the SCR process. Also, nitro-PAHs are converted at the catalytic converter, together with oxygen and the nitrogen-containing reducing agent, to form non-hazardous compounds. This is a reaction pathway in addition to the oxidation of the nitro-PAHs with oxygen to form CO2 and water.


PAH removal from spiked municipal sewage sludge

Researchers from the Institute of Scientific Research, University of Qubec, Canada, studied different processes for removing polycyclic aromatic hydrocarbons (PAHs) from municipal sewage sludge and wastewater. PAHs are strongly adsorbed on to particulate matters of soils, sludge or sediments owing to their strong hydrophobicity, which makes them less bio-available, thus limiting their bioremediation.

Using sludge doped with 11 PAHs at 5.5 mg of each PAH per kg of dry matter, the scientists tested different treatment processes to evaluate the PAH removal performance of each. Two biological processes mesophilic aerobic digestion (MAD) and simultaneous sewage sludge digestion and metal leaching (METIX-BS) were tested to evaluate PAH biodegradation in sewage sludge. In parallel, two quite similar chemical Fenton processes chemical metal leaching (METIX-AC) and chemical stabilization (STABIOX) and one electrochemical stabilization process (ELECSTAB) were tested to measure PAH removal by these oxidative processes. Moreover, PAH solubilization from sludge by the addition of a non-ionic surfactant Tween 80 (Tw80) was also tested.

The best PAH removal rates were obtained by MAD and METIX-BS with more than 95 per cent 3-ring PAH removal after 21 days of treatment.

Addition of Tw80 during MAD treatment increased removal rate of 4-ring PAHs. More than 45 per cent of 3-ring PAHs were removed from sludge by METIX-AC, while about 62 per cent of 3-ring PAHs were removed by ELECSTAB process. However, STABIOX process showed only <35 per cent removal of 3-ring PAHs. None of the processes were efficient for the elimination of high molecular weight PAHs (5-ring or above) from sludge.


Biodegradation of PAHs in petroleum-contaminated soil

Scientists at the National Research Centre for Environmental and Hazardous Waste Management, Thailand, investigated bioremediation of polycyclic aromatic hydrocarbons (PAHs) in petroleum-contaminated soil using tamarind leaf inoculums. Leaves of tamarind and other leguminous trees have been reported to contain several PAH-degrading micro-organisms.

To minimize the amount of leaves added, tamarind leaf inoculums were prepared by incubating the leaves with a sub-sample of contaminated soil for 49 days. Then the efficiency of the inoculums was tested with two soil samples collected from a navy dockyard and railway station. These soil samples had different levels of petroleum contamination. Bioaugmentation treatment was carried out by mixing contaminated soil with the inoculums at the ratio of 9:1. For navy dockyard soil, the concentration of phenanthrene in the inoculated soil was reduced gradually to undetectable level within 56 days; 70-80 per cent of fluoranthene and pyrene remained at the end of the treatment. For railway station soil, which had lower petroleum contamination, PAH degradation occurred faster: the phenanthrene concentration was below detection limit after 28 days.

The treatment also succeeded in reducing the quantities of several hydrocarbons. At the same time, numerous phenanthrene-degrading bacteria, which were used as representatives of PAH degraders, could be observed in both inoculated soils. Higher numbers of bacteria, however, were found in railway station soil, which corresponded with the lower amount of PAHs and higher amount of soil nutrients. The results showed that inoculums prepared from tamarind leaves could be used to degrade PAHs as well as clean-up petroleum contaminated soil.


Promising discovery for PCB clean-up without dredging

Dr. Donna Bedard at the Rensselaer Polytechnic Institute and scientists from Georgia Institute of Technology, the United States, have discovered a bacterium that could remove polychlorinated biphenyls (PCBs) from the environment without dredging. The discovery is a first step towards a bioremediation strategy to naturally detoxify the chemicals without risky removal of the sediments in which they persist. Dr. Bedard, describing the potential breakthrough, said the research will help scientists understand the process by which PCBs have been known to break down naturally in water.

In microcosm studies in her lab, Dr. Bedard found that Aroclor 1260 was being degraded by native sediment microbes. She developed sediment-free enrichment cultures, characterized them in collaboration with Dr. Frank Loeffler and Dr. Kirsti Ritalahti of GeogiaTech. After a series of experiments, the team was able to determine that bacteria in the Dehalococcoides (Dhc) group were responsible for the dechlorination of Aroclor 1260. These microbes replace the chlorine atoms in Aroclor 1260 with hydrogen, which fuels their growth and initiates the PCB degradation process.


Sorbent to prevent dioxin synthesis

DIOX-BLOK from Beco Engineering Company, the United States, is a patented sorbent that prevents new dioxin synthesis in combustion processes. Although modern incineration processes completely destroy dioxins, they form anew as the flue gas cools below 400C. On cool-down, trace organics adsorb on the fly-ash and are converted to dioxins by reaction with the metal chlorides on the surface of the ash.
DIOX-BLOK achieves two things:
  • It starves the fly-ash of dioxin reactants by removing organics before they can be adsorbed by the ash; and
  • Dioxin-contaminated ash is not created: unlike powdered activated carbon (PAC), DIOX-BLOK is chemically inert and adsorbed organics are not converted to dioxins.

DIOX-BLOK is used at rates of from 450-900 g/t of waste burned. The delivered cost of is generally less than, or equal to, the cost of PAC.

Besides, as prevents dioxins from forming, its environmental cost is far less than PAC. Its use with medical / hazardous / municipal waste inci-nerators in dry / wet scrubber units has reportedly shown good results, reducing dioxin emissions to 0.001-0.006 ng/dscm, TEQ.

Contact: Beco Engineering Company, P.O. Box 443, 800 3rd Street, Oakmont, PA 15139, United States of America. Fax: +1 (412) 828 6144




Integrated biological and electrochemical oxidation

Scientists from Aquabiotec GmbH, Germany, have developed an innovative technology for industrial wastewater treatment. The main focus of the Aqua-Biomant process is transformation of persistent organic compounds (bio-recalcitrant COD) into a biodegradable fraction, followed by high-efficiency biological elimination using specialized bacteria. The Aqua-Biomant process integrates two treatments: aerated biological upflow filtration, and electrochemical oxidation technique using boron doped-diamond electrodes. The advantages of the process are high-efficiency COD removal with reduced energy consumption combined with low total residence time.

Contact: Mr. A. Rdiger, Aquabiotec GmbH, Maria-Goeppert Str. 1, D-23562, Lbeck, Germany.


Wastewater treatment with fixed-bed circulation reactor

Fraunhofer IGB, Germany, is testing a fixed-bed circulation reactor in which the fixed bed is partially recirculated from time to time, allowing continuous and trouble-free operation. The wastewater flows through the particle bed from bottom to top and its contents get degraded. To recirculate the particles, the fluid is removed from the top of the reactor and is injected through a nozzle at the bottom of the conveying pipe. By doing so, the particles are hydraulically conveyed upwards and are cleaned owing to the turbulence.

The design of the reactor depends upon the flow properties of the fixed bed packing. The particles differ in the following characteristics: availability, mechanical stability, immobilization of micro-organisms, flow properties and conveying properties. The flow properties of the particles are identified based on the theory of flow of bulk solids. With respect to the design of fixed bed reactors, the following terms are determined: the slope angle of the hopper and the critical area at which no blocking of the flowing particles occurs. Prototypes of the reactors are in operation at industrial companies for assessment.

Contact: Dr. Werner Sternad, Umweltbiotechnologie und Bioverfahrenstechnik, Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB, Nobelstrasse 12, 70569 Stuttgart, Germany. Tel: +49 (711) 970-4110; Fax: +49 (711) 97 04 200



Advances in tube-type fine bubble diffuser design

A majority of wastewater treatment plants around the world use submerged diffused aeration. Because these systems are for the most part submerged in sewage, they must be highly reliable. Stamford Scientific International (SSI), based in the United States, has introduced a new technology that meets this reliability level.
Because of their small size, disc diffusers have less forces acting on them underwater than do larger cantilevered tube diffusers.

Moreover, the method of manufacturing a disc membrane allows great flexibility in rubber compounding and moulding, which can result in a high-quality, tear-resistant and shrink-resistant part. Disc-type fine bubble membrane diffusers have thus gained a name as a highly reliable method of aeration. Limitation of moulding methods has restricted the manufacture of tube diffusers. Therefore, tube diffusers have not gained the same excellent record of longevity and reliability as have disc diffusers. Shrinkage, tearing and stretching do occur with tube membranes.

SSI has developed a way to compression-mould membranes for fine bubble tube diffusers to give them the same advantages as disc diffusers. This method allows the use of less plasticizer in the compound, and the final product shows excellent tear resistance. The diffusers have a plastic diffuser body, made of high temperature resistant and environmentally friendly ABS, with a quick connect type fastener to pipe.

Contact: Stamford Scientific International Inc., 4 Tucker Drive, Poughkeepsie, NY 12603, United States of America. Tel: +1 (845) 454 8171; Fax: +1 (845) 454 8094



Combined system for wastewater with recalcitrant pollutant

In Spain, scientists from Plataforma Solar de Almera-CIEMAT and Universidad de Almera have described a wastewater treatment system having two advanced oxidation processes (AOPs) ozonation and photo-Fenton in combination with a pilot aerobic biological reactor. The system was employed for treating industrial non-biodegradable saline wastewater (TOC ~ 200 mg/litre) containing a-methylphenylglycine (MPG), a bio-recalcitrant compound, at a concentration of 500 mg/litre.

Ozonation tests were performed in a 50-litre reactor with constant inlet of 21.9 g/m3 ozone. Solar photo-Fenton tests were carried out in a 75-litre pilot plant made up of four compound parabolic collector units. The catalyst concentration used in this system was 20 mg/litre of Fe2+ and the H2O2 concentration was kept in the range of 200-500 mg/litre. Complete degradation of MPG was attained after 1,020 minutes of ozonation, while only 195 minutes were required for photo-Fenton.

Biodegradability enhancement of the saline wastewater (>70 per cent biodegradability) was confirmed. Biodegradable compounds generated during the preliminary oxidative processes were biologically mineralized in a 170-litre aerobic immobilized biomass reactor. The global efficiency of AOP/biological combined systems was 90 per cent removal of an initial TOC of over 500 mg/litre.

Contact: Dr. Isabel Oller, Plataforma Solar de Almera-CIEMAT, Carretera Sens, KM 4, 04200 Tabernas, Almera, Spain.



New wastewater treatment technology

SSI, a member of the international consultancy and engineering group DHV of the Netherlands, has introduced an advanced and compact wastewater treatment plant in South Africa. The Nereda technology uses aerobic sludge granules, which settle much faster than the small and sometimes flaky sludges that are normally seen in conventional wastewater treatment plants. The technology can treat both domestic and industrial wastewaters. The final effluents conform to European Union standards.

Unlike the conventional wastewater treatment plants that make use of secondary sedimentation tanks for the biologically activated sludge process, the Nereda process separates the sludge from the treated wastewater inside the reactor tanks. The sludge concentrations and the total quantity of purifying bacteria in the reactor are significantly higher with Nereda technology, which was developed at the Delft University of Technology in the Netherlands.

Compared with conventional plants, the technology is claimed to offer energy savings as high as 30 per cent over and 20-40 per cent lower capital costs associated with construction. No chemicals are needed, and the plant is simple to operate because of extensive automation.


Electro-coagulation of effluent

TI Anode Fabricators, India, has developed the TiChlor-EC system, to increase colour removal rates from water effluents at low capital investment and reduced operating costs. TiChlor-EC is an electro-coagulation process. Its benefits include sludge minimization, treatment of multiple contaminants, disinfection of effluent and low maintenance costs.

The process can treat effluent from textile and dye industry, food processing industry, coal mines and chemicals industry for operations such as:
  • Pre-treatment for reverse osmosis, ultra filtration and nano-filtration;
  • Recirculation of process water and rinse water;
  • Pre-treatment of boiler water;
  • Metal recovery;
  • Radio isotope removal; and
  • Wastewater disinfection.

Typically, TiChlor-EC has achieved the following benchmark reductions:

  • Bacteria from 110 million (standard plate count) in wastewater to zero focal count;
  • Contaminants in oily wastewater from steam cleaning operations, refineries, rendering plants and food processors by 95-99 per cent;
  • Dissolved silica, clays, carbon black and other suspended materials in water by 98 per cent; and
  • Heavy metals (such as arsenic, cadmium, chromium, lead, nickel and zinc) in wastewater by 95-99 per cent.

Contact: TI Anode Fabricators Ltd., 48, Noothanchary, Madambakkam, Selaiyur, Chennai, Tamil Nadu 600 073, India. Tel: +91 (44) 2278 1148; Fax: +91 (44) 2278 1362.


Effluent with heavy metals treated using iron oxide catalyst

The Korea Institute of Geoscience and Mineral Research, the Republic of Korea, has received a United States patent on a method for treating acidic (ph ~1.0) wastewater containing heavy metals Cu, Fe, Ni, Cr or Zn employing a used iron oxide catalyst. The method consists of: adding the used iron oxide catalyst containing at least 70 per cent magnetite to the wastewater at a weight ratio of 1:0.05; stirring the wastewater mixed with the catalyst in a stirrer at 60 rpm for 15 min; and effecting a solid-liquid separation, using a magnet for adsorption and removal of the heavy metals.

The catalyst used in the method is a strongly magnetic iron oxide catalyst used in the synthesis process of styrene monomer. The method is suitable for wastewater containing heavy metals such as metal plating wastewater or mine backwater.



Indigenous plants for bioremediation of closed mines

Shinil Corporation, the Republic of Korea, has developed a technology for the phytoremediation of soils polluted by heavy metals which involves creating mugwort (Common Wormwood or Artemisia vulgaris) cover on the polluted soil. Sulphur, which synthesizes chelate in plants, is supplied through soil improvers (pig manure and sewage sludge) to reduce toxicity and increase resistance when plants absorb heavy metals. The technology was successfully tested in an abandoned zinc mine.

Contact: National Environmental Technology Information Centre, No. 613-2, Bulgwang-dong, Eunpyeong-gu, Seoul, Republic of Korea 122-706. Tel: +82 (2) 3800 553; Fax: +82 (2) 3800 545



Solar bioreactor for groundwater remediation

A pilot-scale recirculation bioreactor has been operating at the Altus Air Force Base (AFB) in Oklahoma, the United States, since late 2003 to address a hotspot of volatile organic compounds (VOCs) in groundwater residing in weathered shale and fractured clay. A solar-powered pump operating in the extraction / collection trench keeps the groundwater recirculating through the 283 m3 bioreactor and into the aquifer to generate high-carbon leachate and enhance VOC biodegradation. Since its start-up, the system has transferred about 1,300 m3/year of organic carbon-enriched leachate from the bioreactor into the aquifer. Groundwater recirculation through the bioreactor has achieved a 98 per cent reduction in trichloroethene (TCE) concentration within the bioreactor and a 90-97 per cent reduction in plume toxicity in hotspot wells between the bioreactor cell and the extraction trench.

Solar pump for groundwater circulation

Prior to project start-up, TCE concentrations in the hotspot were 19 mg/litre, and the plume extended nearly 1,000 m down-gradient of the landfill. The bioreactor was constructed immediately up-gradient of hotspot wells in an excavation of 9 m 9 m extending 3.4 m below ground surface (bgs). The cell was filled with a 1:1 mixture of sand and organic mulch consisting of woody material and cotton-gin trash. At the top of the cell a ground-water distribution system was set up between two layers of geotextile fabric. The cell was capped with a soil and native grass cover.

The bioreactor relies on groundwater recirculation from down-gradient of the hotspot, which is located in the shallow aquifer 3.0-5.5 m bgs. The sites remote location and average solar radiation of 4-5 kWh/m2/day dictated the use of solar power to cut down construction and energy costs. Groundwater recirculation is carried out by a single, photovoltaic-powered, 3 inch submersible pump that maintains an average groundwater flow rate of about 3,500 litres/day. Pollutant degradation is monitored through a network of 18 wells.
Evaluation of the bioreactor performance indicates dissolved organic carbon concentrations increased from <6 mg/litre prior to start-up to 120 mg/litre in shallow wells and 30 mg/litre in deeper wells.

Increased concentrations of cis-1,2-dichloroethene, vinyl chloride and ethene indicate reductive dechlorination of TCE occurs in the bioreactor. For a more complete reductive dechlorination of TCE, a semi-soluble carbon substrate and a bioaugmentation culture were added to the bioreactor.


New process for bioremediation of contaminated soil

Canon Kabushiki Kaisha of Japan has been assigned a United States patent on a new process for remedying a contaminated soil. The new process involves freezing the contaminated region, and then injecting a micro-organism and a liquid/gas agent that is required to augment the micro-organisms ability to decompose the pollutant more rapidly and efficiently. The frozen region is then allowed to gradually thaw.
A possible explanation, yet to be proved, for the process is as follows. When the soil is frozen and then thawed as a pre-treatment, freeze expansion in the pore space will widen the fine pore space of the soil into which the liquid agent will diffuse. Agitation of the soil water retained between the soil particles by this freezing and thawing will accelerate the contact between the injected liquid agent and ground-water. The process, well known in civil engineering field, causes swelling on freezing and consolidation on thawing in the soil.

While a problem to be overcome in civil engineering works, it is favourable for the uniform distribution of a micro-organism. By adopting this freezing step, the present invention can promote the remediation efficiency and shorten the soil remediation period.


Enhanced bioremediation technology

Microbial Groundwater Circulation Wells (mGCW), a concept from IEG Technologie GmbH, Germany, accelerate the natural biodegradation of organic compounds under aerobic or anaerobic conditions. These systems are specifically designed and configured to provide accelerated aerobic, enhanced anaerobic or sequential anaerobic/aerobic reactions. The special design of the wells produces a groundwater convection cell in the aquifer around the remediation well. The groundwater that circulates constantly transports both contaminants and existing degrading bacteria to the well.

Small biologically active carbon reactors can be used inside the well for continuous growth, acclimation and augmentation. These reactors are found to have much higher levels of biodegradation and higher specific growth rates than other attached growth systems. Contaminants are selectively retained in the reactor, facilitating the selection and enrichment of micro-organisms that are capable of degrading pollutants. If necessary, added nutrients can be supplied to the accumulated micro-organisms.

Another advantage of the mGCW is the oxygen-enriched groundwater generated by the system, which enhances the population growth of the micro-organisms in the aquifer, thus accelerating the degradation process. System variations include discontinuous circulation flow, reversing the circulation direction and installing different bioreactor configurations. These variations enable the technology to be easily customized to different contamination sites.

Contact: IEG Technologie GmbH, Hohlbachweg 2, Gruibingen73344, Germany. Tel: +49 (7335) 96976-0; Fax: +49 (7335) 96976-40



Bioremediation of hydrocarbon-contamination

Exxon Research and Engineering Company, New Jersey, has secured a United States patent on its invention that provides an enhanced biodegradation process by applying to petroleum-contaminated water or soil microbial nutrients in controlled release. The process is capable of releasing the microbial nutrients over a sustained period of time, for example 1-6 months, which at 25C is a substantially linear rate.

The rate of release of microbial nutrients, which is typically less than 5 per cent per day, can be increased by raising the temperature.

The nutrients may include one or more nitrogen sources, such as urea and ammonium nitrate, and optionally phosphorous sources such as phosphates. Typically the nitrogen and phosphorous sources will be combined to provide an N:P ratio, preferably, of 10:1. Optionally, the nutrient cocktail may also contain micronutrients such as magnesium, iron, manganese and calcium at very low levels. The nutrients are coated with a material like an elastomeric sulphonated polymer such as ethylene-propylene diene terpolymer or EDPM that controls the release of nutrients to the environment.


Vegetable oil as a bioremediation amendment

At University of Waterloo, Canada, biologists have studied the feasibility of using peanut (groundnut) oil as a cost-effective, non-toxic and biodegradable extractant for the remediation of soil contaminated by polycyclic aromatic hydrocarbons (PAHs). The scientists found that extraction efficiency was higher than 90 per cent when peanut oil at concentrations of 2.5-20 per cent was used to remove anthracene from garden soil. Optimal pH values for these extractions were 6 and 7.

When soil spiked with a combination of 10 PAHs at 100 g/g was extracted with peanut oil at different temperatures, total PAH extraction efficiency increased from 51.5 per cent at 20C to 81.4 per cent at 60 C. A double extraction of weathered soil from a creosote-contaminated site using 5 per cent peanut oil, followed by another extraction with 5 per cent oil was better than a single 10 per cent oil extraction. Based on the results of the study, a process was conceptualized for the treatment of PAH-contaminated soil.



Selective non-catalytic reduction process

Selective catalytic reduction (SCR) or selective non-catalytic reduction (SNCR) can be employed to reduce the levels of nitrogen oxides (NOx) present in the flue gas. The SNCR process, developed by Martin GmbH of Germany, reduces NOx produced during combustion to nitrogen and water by injecting aqueous ammonia (NH4OH), a reducing agent, into the furnace. NOx values of up to 70 mg/Nm3 have been achieved using this process.

The agent is injected in the temperature range of 850C to 1050C. A second mass flow is required to get a uniformly fine distribution. Both softened fresh water and compressed air may be used for this purpose in the system. The two mass flows are combined in a mixing chamber directly up-stream of the nozzle head. This arrangement ensures low dead times for control of the aqueous ammonia mass flow, as well as optimized consumption and low aqueous ammonia slip in the flue gas. The control system ensures that injection always takes place in the optimum temperature range as a function of the current furnace temperature.

Contact: Martin GmbH fr Umwelt und Energietechnik, Leopoldstrae 248, D-80807 Mnchen, Germany. Tel: +49 (89) 35617-0; Fax: +49 (89) 35617-299



Multi-pollutant treatment technology

EMx, from EmeraChem, the United States, is a multi-pollutant technology that significantly reduces such pollutants as nitrogen oxides (NOx), sulphur oxides, carbon monoxide, volatile organic compounds as well as particulate matter for gas-fired turbines to ultra low levels (< 1 ppm for all criteria pollutants). The United States Environmental Protection Agency declared this technology as the Lowest Achievable Emission Rate for NOx abatement, establishing the standard against which all future emission reduction means will be measured.

EMx is a continuous process that is designed to achieve the required emission reduction at the maximum NOx flow rate. It does not require a complex feedback control loop, and has additional catalyst capacity, providing for future regulatory certainty. EMx is also claimed to be the most effective ammonia-free reduction technology available today for gas turbine, reciprocating engines and industrial and utility boilers. It avoids the fouling of downstream heat transfer surfaces and guarantees net reduction of particulate matter.

Contact: EmeraChem, 1729 Louisville Dr., Knoxville, Tennessee 37909, United States of America. Tel: +1 (865) 246 3000; Fax: +1 (865) 246 3001.


Microwave process for NOx abatement

The CHA Corporation, the United States, has recently completed a small business innovation research programme to investigate the feasibility of using a novel microwave based filter device to remove and destroy unwanted by-products of combustion in exhaust gases. A Corning ceramic monolith soot filter that has about 90 per cent soot removal efficiency was placed in a housing that allowed for microwave regeneration. Two filters were set up in parallel into the exhaust piping of a diesel engine. After 4-hour periods of operation, the filters were successfully regenerated employing microwave energy for more than 50 cycles.

A prototype device for destroying ni-trogen oxides (NOx) in the exhaust gas generated by a diesel engine (58 hp) was constructed and tested. The NOx control device comprised two separate fixed-bed reactors filled with catalyst beads. In the first, a Pt/Pd catalyst was used to convert nitric oxide (NO) into nitrogen dioxide (NO2) in the diesel exhaust. A reducing agent and microwaves were supplied to the second reactor, containing alumina-SiC pellets coated with a Pt/Rh/Pd catalyst, to destroy NO2. As the NO oxidation efficiency (45-55 per cent) is suppressed by the high concentration of water in diesel engine exhaust, NOx destruction efficiencies were only 30-40 per cent, 10-20 per cent lower than the NOx destruction obtained from smaller reactors.

Test results obtained for this prototype microwave deNOx device clearly identified techno-economic advantages, as well as technical difficulties, of applying microwave-based filter devices to control pollutants in diesel exhaust. Preliminary experimental data indicate that the microwave reactor system that was developed for NOx destruction can be also used for destroying waste rocket fuels including hydrazine and unsymmetric dimethylhydrazine in nitrogen or air streams.


Selective catalytic reduction package/catalyst

irProtekt Ltd., the United Kingdom, supplies the total selective catalytic reduction (SCR) package or the SCR catalyst for control of nitrogen oxides (NOx) emission. The catalyst technologies used are all tried and backed up by the manufacturing and quality control standards from the largest automobile catalyst manufacturer in the world.

The basic reactions that occur are as follows:
4 NH3 + 4NO + O2  4 N2 + 6 H2O
8 NH3 + 6 NO2  7 N2 + 12 H2O

These reactions break down NOx into harmless nitrogen and water. Urea is used as the reducing agent since it is generally unaffected by the oxygen present in the exhaust gases and is readily available. In most exhaust gases, virtually all of the NOx present is in the form of nitric oxide (NO). The optimum temperature for the reduction of NOx using a zeolite/base-metal catalyst is about 350-550C.

The main advantages of the SCR process are that the catalyst has a long life and provides a high NOX removal rate, and extensive modifications to the engines are avoided. The underlying principle of this type of catalytic process is the use of active catalytic sites on which the reactant species are adsorbed. This allows combination of the reactant species at much lower gas temperatures than needed for uncatalysed reactions.

Contact: AirProtekt Ltd., Newton Hall, Newton, Cambridgeshire CB2 5PE, United Kingdom. Tel: +44 (1223) 872 933; Fax: +44 (1223) 872 934



A Multi-functional carbon filter process for flue-gas clean-up

Researchers from the University of Wyoming, the United States, have developed and evaluated a multi-functional carbon filter process, or MCFP, for separating carbon dioxide (CO2) and other pollutants, such as NOx, SOx and mercury, of power plant flue-gas.

The cost of the recovered CO2 using a carbon-rich adsorbent at ambient pressure can be reduced by a factor of 2 or more, relative to an amine-absorption benchmark. Such an adsorbent is selective at near-ambient temperatures, easy to keep at constant adsorption temperature, and easy to recover by direct steam heat because its heat of adsorption is very low. Besides, MCFP is relative-ly insensitive to flue-gas moisture, which poses a serious problem for more hydrophilic sorbents such as zeolites. Based on the data from their laboratory experiments, the researchers concluded that MCFP technology can be integrated with a coal power plant for producing an enhanced oil recovery grade CO2.


Regenerative thermal oxidation process

The Biotox process, from Biothermica Technologies Inc., Canada, is a patented regenerative thermal oxidation (RTO) technology for treating emissions of volatile and condensable organic compounds (VOCs & COCs) and corrosive emissions. In more than 20 installations, it has successfully demonstrated destruction efficiencies of more than 99 per cent and energy efficiencies greater than 90 per cent for flows varying from 2,000 to more than 150,000 actual cubic feet per minute.

The Biotox RTO process consists of oxidizing in a combustion chamber the VOCs and COCs contained in the industrial emissions, and recovering usable heat from combustion gases by means of ceramic beds. The recovered heat can then be used to pre-heat entry gases, thanks to the efficient heat transfer between entry and exit gases.

The typical combustion temperature is 800C while the residence time is one second. The combustion gases, mainly composed of water and carbon dioxide (CO2), are then released into the atmosphere. A hot gas recirculating system is installed to raise the COCs to a temperature sufficient for avoiding condensation in the bottom of the beds.

Advantages of the patented Biotox process include:
  • Energy recovery rates reaching 95 per cent, along with substantial fuel savings and reductions in greenhouse gas;
  • Low emissions of NOx and CO2;
  • System adaptable to variations in VOC / COC concentrations; and
  • Choice of ceramics to suit specific applications.

Contact: Biothermica Technologies Inc., 426 Sherbrooke East, Montreal, Quebec H2L 1J6, Canada. Fax: +1 (514) 488 3125



Electron beam method for SOx and NOx reduction

Chubu Electric Power Co. of Japan has devised an electron beam process for the simultaneous removal of nitrogen oxides (NOx) and sulphur oxides (SOx) from flue-gas. It is a dry process without the need for any wastewater treatment or expensive denitrification catalyst. The process yields, as a by-product, a valuable fertilizer. A pilot plant of the system, with a flue gas treatment capacity of 12,000 m3N/h, has demonstrated a SOx / NOx removal efficiency of more than 94 per cent and 80 per cent, respectively.

After the floating ash in flue gas is roughly removed in the dry type electrostatic precipitator, the gas flows through the GGH extractor to be cooled to around 110C. In the spray cooler, the gas is cooled further to 60-70C, the desirable level of temperature for desulphurization reaction. Then the necessary quantity of ammonia for desulphurization and denitrification is added. The gas then moves into the process vessel, where an electron beam is applied to it. In the process vessel, SOx and NOx are oxidized to become sulphuric acid and nitric acid, respectively, which in turn react with ammonia to produce fine particles of ammonium sulphate and ammonium nitrate.

After the fine particles are collected and separated from the flue gas in the dry type electrostatic precipitator and bag filter, the purified gas is discharged to the atmosphere by the booster fan through the stack. The test results from the pilot plant have proved that the system fully satisfies the requirements for flue gas treatment in coal-fired power stations.


Ceramic filters

Ceramic filters from Caldo Environmental Engineering Limited, United Kingdom, are high-temperature devices for the continuous removal of particulates from air or other gases. Caldo supplies a range of filter sizes and employs a modular approach for larger gas flows. The addition of sorbent powder enables the filters to function as dry scrubbers in waste gas applications.

The ceramic filter element is vacuum-formed using alumino-silicate ceramic fibres as a 1,000 mm long tube, flanged at one end and closed at the other. It is stable even under extreme conditions of temperature (up to 900C) and chemical corrosion (except hydrofluoric acid). The elements hang vertically in the filter vessel from the header plate. In use the hot gas is sucked through the filter medium from outside to inside, depositing the particles on the outer surface of the medium. At controllable intervals a sharp pulse of air is blown back down the inside of the filter element to detach the solids accumulated on the outer surface of the filter elements. The number of filter elements in the filter vessel determines the capacity of the filter. Caldo has standard designs for 64, 120, 214 and 256 element filters.

Acid gases a common gas-phase pollutant can be very effectively removed by the addition of lime or sodium bicarbonate to the gas upstream of the ceramic filter. Both chemicals react well with HCl, HF and H2SO4 and remove a proportion of any NOx that is present.
Ceramic filters are useful on nearly all high-temperature processes in which the exhaust gas may contain smoke, fume or dust. Typical applications include:
  • Incineration of wastes;
  • Cleaning of fuel gases from pyrolysis or gasification processes;
  • Protection of catalysts in chemical processes;
  • Cleaning of gases from metallurgical furnaces; and
  • Collection of products manufactured through condensation of hot gases.

Contact: Caldo Environmental Engineering Limited, No.1 Worcester Court, Saxon Business Park, Hanbury Road, Bromsgrove Worcestershire B60 4AD, United Kingdom.


Managing Healthcare Waste A Practical Approach

Managing Healthcare Waste A Practical Approach is a must-read for those interested in infection control and management of medical wastes. The book offers a detailed overview of technical elements in health care waste management system, based on the life cycle approach.

Contact: KW Publishers Pvt. Limited, 5A/4A, Ansari Road, Daryaganj, New Delhi 110002, India. Tel: +91 (11) 2326 3498; Fax: +91 (11) 2326 3498



Persistent Organic Pollutants in Asia, 7

This book contains large amounts of data obtained through environmental monitoring of persistent organic pollutants (POPs) in 10 Asian countries and Australia and explored using principles of environmental chemistry, toxicology and risk assessment. It also includes accounts of current governmental policies, monitoring and surveillance programmes, impacts on human health, and cross-boundary transport of POPs in these countries.

Contact: Customer Service Department, Elsevier B.V., 3 Killiney Road #08-01, Winsland House I, Singapore 239519. Tel: +65 6349 0222; Fax: +65 6733 1510


Chemical Water and Wastewater Treatment IX

This book, the Proceedings of the 12th Gothenburg Symposium, provides information on scientific and practical experience in integrated water resources management. It is the outcome of collective experience and know-how exchanged between experts in the field of water technology from all over the world, from the Americas, from Central and Southern Africa, from Europe and from different parts of Asia. The symposium and this book differ from its predecessors in that the focus is also on key non-technical aspects that may influence technological solutions. The book is a valuable resource for those interested in chemical water and wastewater treatment technology.

Contact: International Water Association, Alliance House, 12 Caxton Street, London SW1H 0QS, United Kingdom. Tel: +44 (207) 654 5500; Fax: +44 (207) 654 5555



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