Wastewater Technology Centre Research Articles

Valorization of Foundry Sand in Clay Bricks at Industrial Scale

SummaryIn this article, foundry sand as waste material has been valorized in ceramic brick manufacturing at industrial scale. The employment of a waste coming from one industry as an input for another is one of the key concepts of industrial ecology. To study the environmental behavior of the ceramic bodies in different life cycle stages, three leaching tests have been developed. We used an EN 12457 equilibrium leaching test with distilled water and a Wastewater Technology Centre acid neutralization capacity (WTC‐ANC) leaching test with different acidic leachates to carry out the environmental evaluation under different granular scenarios to ascertain the possibilities of the reuse or disposal of this granular material at the end of its useful life (end‐of‐life stage). Finally, we used a NEN 7345 diffusion leaching test for construction materials, with the aim of studying the environmental assessment at the use stage. Regulated pollutants in both stages have been evaluated. Furthermore, other soluble salts have been analyzed because they are closely related to the efflorescence phenomenon in bricks. Results indicate that core and green sand from the foundry industry can be used to replace clay content in construction materials, and that these foundry‐sand‐based ceramics improve some soluble salt results. Despite this fact, at the end‐of‐life stage in an inert waste landfill, lead, arsenic and chromium can be an environmental problem, both for commercial bricks and for foundry‐sand‐based bricks. This work can contribute to the determination of viability of sustainable processes of brick manufacturing that use foundry wastes as raw materials.

Laboratory pilot scale study for H2S removal from biogas in an anoxic biotrickling filter

The purpose of this laboratory pilot scale study at the Wastewater Technology Centre (WTC), Environment Canada, Burlington, ON was to investigate the anaerobic biological removal of H2S from biogas under real-time operating conditions. Biogas produced in a 538 litre pilot anaerobic digester was continuously fed into a 12 litre biotrickling filter containing plastic fibres as packing bed media. The process was monitored for several months. The biogas flowrate and H2S concentration ranged between 10 to 70 L/h and 1,000 to 4,000 ppmv respectively over the course of the test period. Nitrate-rich wastewater from a pilot scale sequencing batch reactor effluent was used as the nutritive solution for the biotrickling filter. The paper presents the influence of several operational parameters such as biogas flowrate, hydrogen sulphide concentration and composition of nutrient solution on process performance. To date, our results show H2S removal rates up to 100% without adverse effects on the methane concentration of the biogas. No system deterioration was observed over long term operation. This non-conventional technology is very promising and could be considered for full scale applications.

The Urban Drainage Program of Canada’s Great Lakes 2000 Cleanup Fund

Abstract Since 1990, Canada’s Great Lakes 2000 Cleanup Fund, which is administered by Environment Canada, has been supporting the development and implementation of cleanup technologies to control municipal pollution sources, to clean up contaminated sediments, and to rehabilitate fish and wildlife habitats. These efforts are focused on Canada’s 16 Great Lakes Areas of Concern (AOCs) identified by the International Joint Commission for priority cleanup action and restoration of beneficial uses. Remedial Action Plans (RAPs) developed by federal/provincial teams and the public provide the strategy for restoring the beneficial uses of the AOCs. Impairments in beneficial uses in the AOCs have been, in part, caused by discharges from combined sewer overflows (CSOs), Stormwater and sewage treatment plants (STPs). To assist municipalities in addressing the problems posed by urban drainage (CSOs and Stormwater), the Cleanup Fund’s Urban Drainage Program has been supporting the development and demonstration of innovative, cost-effective technologies and approaches. These projects include high-rate treatment of CSOs, real-time control of CSOs, performance assessment of Stormwater treatment technologies, pollution prevention and control plans, and development of Stormwater management planning tools for urban areas. These projects are carried out in collaboration with the Ontario Ministry of the Environment, municipalities, professional groups, universities and conservation authorities and other Environment Canada’s facilities (National Water Research Institute and Wastewater Technology Centre). The Urban Drainage Program has been instrumental in advancing the state of the art in CSO and Stormwater management in Ontario. Projects supported under the program have quantified pollutant loadings from municipal wastewater sources in several Ontario Areas of Concern, provided hard data on the performance of best management practices for Stormwater treatment, identified and evaluated new cost-effective technologies for CSO reduction and Stormwater treatment, and developed strategies and decision-making tools for Stormwater management The work done through the Urban Drainage Program is making it possible for Great Lakes communities to achieve important environmental objectives at significantly lower cost As a result, the communities should be able to achieve many of these objectives much earlier than they would have if their choices had been limited to more conventional and capital-intensive solutions. Although the program has focused on the needs of Areas of Concern in the Great Lakes basin, the lessons learned there can easily be applied to communities in other parts of the country and around the world.

Variability of field solidified waste

The properties of solidified waste prepared in the field can be anticipated to be more variable than those of solidified samples prepared in the laboratory, because of the greater difficulty in controlling parameters such as untreated waste and binder homogeneity, accuracy of dosage, mixing efficiency, changes in handling characteristics caused by scale-up, etc. However, there is little information available regarding the effect of field variability on solidified waste properties. In a field trial conducted by the Wastewater Technology Centre it was found that the proportions of the waste (electric arc furnace dust) and binder (activated blast furnace slag) could be controlled within 2%, expressed as a fraction of the mix. Comparison of comprehensive physical and chemical test results for laboratory and field solidified specimens of electric arc furnace dust showed that the physical properties of the field solidified material were sensitive to changes in water addition. Chemical properties and leachability were most affected by changes in pH and acid neutralization capacity. However, both physical and chemical properties remained within the desired range.

Near bed solids transport in sewers

This paper describes the results of three sewer sediment studies, carried out in Dundee, financed by the Engineering and Physical Sciences Research Council (EPSRC) and the Water Research centre (WRc). The work was carried out by the University of Abertay Dundee (Wastewater Technology Centre) as part of a collaborative research project undertaken with the University of Newcastle and the University of Sheffield. In Dundee, through collaboration with the sewerage system operator (Tayside Regional Council Water Services Department), three field sites have been established in interceptor and trunk sewer sites, since 1992, to monitor, as closely as possible, sediment and other pollutant erosion, their transport and the effects of first flushes. The physical and biochemical nature of the material being transported near the bed of real sewers has been measured. The importance of this mode of transport, in terms of mass transported and pollutant potential, is demonstrated based on data collected from the Dundee system sites. Comparisons are made between measured transport rates at the bed, at sites with and without deposited beds, with results obtained by applying empirical relationships developed to predict near bed transport in laboratory studies. A modified relationship is proposed which best fits the Dundee system data.

Sewer sediments: preparation methods for enumerating bacteria

In the UK, the Urban Pollution Management programme has contributed to extensive international research concerning solids associated with urban drainage systems. Since 1986, as part of the UPM programme, research undertaken at the Wastewater Technology Centre, University of Abertay Dundee, has focused primarily upon the characteristics and movement of solids and associated pollutants in combined sewer systems. These investigations have considered the behaviour of sediments and their attached pollutants during dry weather and storm flow conditions, and also the degree of pollutants associated with, and released from sewer sediments during periods of increasing sediment bed shear stresses. Data collection and sample analysis were driven by requirements specified for the development of a United Kingdom sewer flow model termed “MOSQITO”, with the basic chemical parameters ie; COD, BOD and ammonia, of sewage and sewer sediments. A data collection programme is described which assesses the feasibility of using combined sewer sediment preparation protocols, normally used for these chemical analyses, to enumerate bacterial indicator organisms present in deposited sediments. The data were analysed to investigate whether the methods used were precise in terms of repeatability, prior to more extensive studies being undertaken to provide sewer sediment data for bacterial numbers.

Near bed solids transport in sewers

This paper describes the results of three sewer sediment studies, carried Out in Dundee, financed by the Engineering and Physical Sciences Research Council (EPSRC) and the Water Research centre (WRc). The work was carried out by the University of Abertay Dundee (Wastewater Technology Centre) as part of a collaborative research project undertaken with the University of Newcastle and the University of Sheffield.In Dundee, through collaboration with the sewerage system operator (Tayside Regional Council Water Services Department), three field sites have been established in interceptor and trunk sewer sites, since 1992, to monitor, as closely as possible, sediment and other pollutant erosion, their transport and the effects of first flushes.The physical and biochemical nature of the material being transported near the bed of real sewers has been measured. The importance of this mode of transport, in terms of mass transported and pollutant potential, is demonstrated based on data collected from the Dundee system sites. Comparisons are made between measured transport rates at the bed, at sites with and without deposited beds, with results obtained by applying empirical relationships developed to predict near bed transport in laboratory studies. A modified relationship is proposed which best fits the Dundee system data.

Sewer sediments: Preparation methods for enumerating bacteria

In the UK, the Urban Pollution Management programme has contributed to extensive international research concerning solids associated with urban drainage systems.Since 1986, as part of the UPM programme, research undertaken at the Wastewater Technology Centre, University of Abertay Dundee, has focused primarily upon the characteristics and movement of solids and associated pollutants in combined sewer systems.These investigations have considered the behaviour of sediments and their attached pollutants during dry weather and storm flow conditions, and also the degree of pollutants associated with, and released from sewer sediments during periods of increasing sediment bed shear stresses. Data collection and sample analysis were driven by requirements specified for the development of a United Kingdom sewer flow model termed “MOSQITO”, with the basic chemical parameters ie; COD, BOD and ammonia, of sewage and sewer sediments. A data collection programme is described which assesses the feasibility of using combined sewer sediment preparation protocols, normally used for these chemical analyses, to enumerate bacterial indicator organisms present in deposited sediments. The data were analysed to investigate whether the methods used were precise in terms of repeatability, prior to more extensive studies being undertaken to provide sewer sediment data for bacterial numbers.

A proposed protocol for evaluation of solidified wastes

Solidification technologies are potentially useful for improving the chemical and physical properties of hazardous wastes to the extent that they are suitable for less expensive disposal or even utilization. Unfortunately, in most jurisdictions worldwide, there is no mechanism for reclassifying a treated, previously hazardous waste, as non-hazardous. In response to the need for such a mechanism, the Wastewater Technology Centre has proposed a protocol of test methods for cement-based solidified wastes. The suggested test methods examine partitioning of contaminants as a result of their chemical speciation, and potential for slow release of contaminants, based on the mobility of the contaminants in the solidified waste matrix, and the durability of the matrix. Most of the suggested tests are standards from the fields of hazardous and radioactive wastes, some of which have been evaluated in a cooperative study with vendors of solidification processes, initiated by Environment Canada. Based on the performance of a solidified product in the tests, it is considered for four utilization and disposal scenarios unrestricted utilization, controlled utilization, segregated landfill and sanitary landfill. The protocol represents a first attempt to develop a management tool for solidified wastes that accounts for their physical and leaching characteristics, in the context of different disposal scenarios.

Quality analysis/quality control tests for field stabilization/solidification — 1. Dry cementing additives

As part of a field validation study of their proposed protocol for solidified waste evaluation, which will correlate laboratory test results with field behaviour, the Wastewater Technology Centre investigated the applicability of several rapid tests for quality analysis and control of the field solidified waste. A pilot-scale landfill was constructed and 63 m 3 solidified arc furnace dust placed in it using a cementing system consisting of blast furnace slag, lime, silica fume and sodium metasilicate. The ground blast furnace slag, hydrated high calcium lime and silica fume were pre-blended before being trucked to the field site and the sodium metasilicate was added in the mixing water. Available lime index using the rapid sugar method (ASTM C-25) and measurement of specific gravity were used to determine the effect of mixing procedures and transportation on the homogeneity of the blended dry additives. Experimental results indicate that the rapid sugar method can give an accurate analysis of lime content in the pre-blended additives. There is a good linear relationship between the slag content and specific gravity because the lime and silica fume have a similar specific gravity. However, the agglomeration of the blended additives affects the accuracy and precision of the method.

PAH removal using soil and sediment washing at a contaminated harbor site

AbstractIn tests conducted for the Canadian government on sediment from Thunder Bay Harbour, Ontario, the BioGenesis washing process was demonstrated to be effective in remediating contaminated harbor sediments. Removal efficiencies for 16 polyaromatic hydrocarbons (PAHs) in concentrations exceeding 4,000 parts per million averaged 90 to 95 percent in pilot tests. These results are significant because, until now, washing processes have not proven effective in cleaning the small‐size particles of silt and clay that make up most underwater sediments. In Thunder Bay, 81 percent of the particles were less than 38 microns (medium silt) in size. The tests on Thunder Bay sediment were conducted under the auspices of the Contaminated Sediment Treatment Technology Program of Environment Canada's Wastewater Technology Centre. Thunder Bay Harbour is one of 43 “areas of concern” identified by the International Joint Commission of Great Lakes Water Quality.

Aerobic and Anaerobic Biological Treatment and Characterization of Condensate Wastewaters from the Taciuk Oil Process

Abstract Bench-scale investigations were conducted at Environment Canada's Wastewater Technology Centre to assess the feasibility of using biological activated sludge systems to treat fractionator sour water (PW5) and processor preheat steam vent water (Preheat) from the AOSTRA Taciuk Process when applied to bitumen recovery from oil sands. The PW5 wastewater sample was approximately 10 times more concentrated with regard to COD, TOC and ammonia concentrations than the Preheat sample. Phosphorus was lacking in each wastewater. High levels of cyanide were present in the Preheat sample and high levels of zinc in the PW5 sample. Aerobic treatment of the Preheat wastewater was shown to be feasible with regard to organic carbon removal. At a sludge retention time (SRT) of 20 days and hydraulic retention times (HRTs) ranging from 0.9 to 2.4 days, organic carbon removal of the Preheat wastewater in terms of BOD5 was greater than 95%. Nitrification was also achieved with ammonia removals of greater than 95%. The PW5 treatment system, operated at a 20-day SRT and HRTs ranging from 5 to 10 days, achieved BOD5 removals of approximately 90%. However, residual carbon levels of approximately 200-400 mg/L remained in the effluent. The addition of powdered activated carbon at the 5-day HRT level did not significantly improve system performance. Excessive foaming and effluent suspended solids losses contributed to operating problems. Nitrification was not established, possibly due to high influent ammonia values. Anaerobic toxicity testing showed that the Preheat wastewater was a relatively weak substrate which did not inhibit anaerobic microorganisms. The PW5 wastewater was toxic to these organisms and this was a substrate concentration-related phenomenon.

Anaerobic and Aerobic Treatability of High-Yield Sulphite Spent Liquor

Abstract Several higher-yield sulphite pulp mills in Canada discharge untreated spent cooking liquor containing substantial amounts of dissolved organic pollutants. The Wastewater Technology Centre has conducted a study on the chemical characterization and biotreatability of spent liquor from a high-yield sulphite (HYS) and an ultra-high-yield sulphite (UHYS) pulping operation. Batch bioassays revealed a high degree of aerobic treatability, including filterable COD removals of 60-65% and 70–75% from HYS and UHYS waste liquor, respectively. Anaerobic treatment was found to be much less suitable as evidenced by severely inhibited methane production rates and impaired treatment efficiencies during batch serum bottle testing of 5-20% v/v spent liquor. Anaerobic bioassays over a 70-day incubation period with 5% HYS waste liquor produced relatively low filt-COD and filt-BOD5 removals of 30% and 75%, respectively. Even poorer performance results were observed at increased test concentrations. Although the degree of anaerobic treatment was somewhat better for the lower-strength UHYS liquor, a high level of dilution (i.e., 10-20 fold) was still required. The elevated concentrations of total sulphur and particularly sulphite-sulphur of 13.5 and 4.8 g/L respectively in HYS spent liquor, and of 3.6 and 1.3 g/ L in UHYS liquor, were apparently responsible for much of the toxic effects on the unacclimated anaerobic biomass.

Book Reviews: INVESTIGATION OF TEST METHODS FOR SOLIDIFIED WASTE EVALUATION—A COOPERATIVE PROGRAM. By J. A. Stegemann and P. L. Coté. Published by Wastewater Technology Centre, Environment Canada, Ottawa, Canada, 1981, Report EPS 3/HA/8 January, 116 pp. Also available in French. Reviewed by R. B. Dean, Associated Editor, Waste Management & Research

Book Reviews: INVESTIGATION OF TEST METHODS FOR SOLIDIFIED WASTE EVALUATION—A COOPERATIVE PROGRAM. By J. A. Stegemann and P. L. Coté. Published by Wastewater Technology Centre, Environment Canada, Ottawa, Canada, 1981, Report EPS 3/HA/8 January, 116 pp. Also available in French. Reviewed by R. B. Dean, Associated Editor, Waste Management & Research

Treatability evaluation of coking plant effluent

Abstract The Algoma Steel Corporation decided to build a biological treatment plant to reduce the amount of phenolics discharged from its cooking plant operation to St Mary's River. The aerobic fluidized bed (AFB) process has been selected for this application. Due to short implementation schedule, a detailed pilot plant evaluation of the wastewater treatability was not possible. A detailed evaluation of a similar waste from Dofasco Inc. in Hamilton, however, was conducted by Dearborn at the Wastewater Technology Centre. Consequently, the treatability of Algoma and Dofasco wastewaters was compared in laboratory tests over a period of 2 months. The results show that the treatability of both wastewaters were similar and provided assurance that the fluidized bed reactors will have adequate capacity to achieve the desired results.

Book Review: COMPENDIUM OF WASTE LEACHING TESTS. Published by the Wastewater Technology Centre, Environment Canada, 1990. Available from Environmental Protection Publications, Conservation and Protection, Environment Canada, Ottawa, Ontario, Canada K1A OH3, 85 pp. Also available in French. Reviewed by R. B. Dean

Book Review: COMPENDIUM OF WASTE LEACHING TESTS. Published by the Wastewater Technology Centre, Environment Canada, 1990. Available from Environmental Protection Publications, Conservation and Protection, Environment Canada, Ottawa, Ontario, Canada K1A OH3, 85 pp. Also available in French. Reviewed by R. B. Dean

Optimizing Polymer Consumption in Sludge Dewatering Applications

As we move into the 1990's, upgrading of existing wastewater treatment plants is becoming a very important consideration. Although upgrading can take many forms, one of the most economic is to optimize the performance of the existing equipment and structures. In the realm of sludge dewatering, also an increasingly important topic, an area which has received little attention in the past is the control of the sludge conditioning process prior to dewatering. In conjunction with the Wastewater Technology Centre in Burlington, Canada, ZENON Water Systems Inc. has developed the Sludge Conditioning Controller (SCC) to fulfill this need in the wastewater marketplace. A description of both the hardware and software aspects of the SCC are presented. In addition, typical operating performance of the microprocessor-based system is shown. Experience with full scale systems has revealed that the benefits associated with the SCC far exceed the original objective of saving polymer. The others include automation of the dewatering device operation, increased capacity, and more uniform performance of the dewatering machine.

Conversion of Sludge to Oil: A Novel Approach to Sludge Management

Experiments at the Wastewater Technology Centre have shown that low temperature conversion of sludge to oil represents a promising alternative to sludge incineration. A 1kg/h bench-scale reactor produced oil yields ranging from a low of 13% for an anaerobically digested sludge to a high of 46% for a mixed raw sludge. Char yields ranged from 40 to 73% at the optimum operating temperatures. Preliminary results from a 40 kg/h pilot plant were similar to those obtained on the bench-scale system with the same sludges. The economics of the conversion process are compared with those for incineration. The impact of the “sludge to oil” technology on the design of sludge management systems is also discussed.

Total Dissolved Solids Removal From Water Produced During The In Situ Recovery Of Heavy Oil And Bitumen

Abstract Based on a preliminary economic and technical comparison, evaporation, membrane processes and freeze desalination were identified as the most attractive technologies for removing total dissolved solids (TDS) from produced water. Vapour compression evaporation appeared to be the most cost-competitive. Subsequently, laboratory-scale experiments on the evaporation of produced waters were conducted on four produced water samples from various locations in Alberta and Saskatchewan he evaporator consisted of a 4.6 m long titanium tube; 50.8 mm o.d. by 6.3 mm wall thickness, heated by steam to effect evaporation. Feed flow rate was 19 L/h and each run lasted 1.5 days. Feed TDS levels ranged from 12 000 to 64 000 mg/L. Oil and grease concentrations ranged from 10 to 310 mg/L. Depending on the level of scaling components in the produced water, the evaporator was run in a seeded or unseeded mode of operation. Produced water recoveries ranged from 67% to 93%. Heat transfer coefficients observed ranged from 3650 to 4050Im2.K. No operational problems with respect to foaming and fouling were observed. A preliminary cost estimate, based on heat transfer design parameters obtained, indicated that the capital cost would be approximately $8.9 million (1986 Canadian dollars) for a plant treating 3800 m31d 0/ produced water. Estimated annual operating costs ranged from $1.2 to $1.9 million and were dependent on the produced water characteristics and the mode of operation of the evaporator. Introduction The production of heavy oil and bitumen by in situ methods using steam flooding Or steam stimulation generates large volumes of water called "produced water". The most attractive strategy from an environmental viewpoint to handle this water is to reuse it as feed water for steam generation. However, at some locations in Alberta and Saskatchewan, produced water contains very high levels of total dissolved solids (TDS), with concentrations > > 8000 mg/L(1). This water is unsuitable for reuse in oilfield steam generators unless it can be treated to reduce the TDS concentrations to approximately 8000 mg/L or less(2). As part of an ongoing program dealing with the characterization and treatment of produced water, Environment Canada's Wastewater Technology Centre (WTC) is currently evaluating the technologies available for removing TDS from produced water. This paper presents the results of the first two phases of this evaluation:a literature review which identified the most promising processes, based on technical and economic factors, anda laboratory-scale experimental evaluation of vapour compression evaporation-one of the most promising processes. Status of Produced Water Recycling In situ recovery of heavy oil-bitumen by steam stimulation (or steam flooding) can generate 2 to 20 times as much water as oil, although in most cases, this ratio is approximately four(3, 4). Hence, the volume of produced water generated at some of these sites can be substantial. Water requirements for steam generation at these facilities can also be considerable. The water required for this purpose is approximately 5 to 6 times the volume of oil produced(5).

Evaluation of Heavy Metal Leachability from Solid Wastes

Future management options for residual inorganic solid wastes are likely to include land disposal. While the environmental ramifications of this option are now better understood, additional data is required to permit a thorough assessment of contaminant leachability from solid wastes. As part of this data gathering exercise, Environment Canada's Wastewater Technology Centre has been actively researching and developing test methods designed to measure intrinsic waste properties that affect contaminant leachability, such as metal solubilities and speciation. Based on this approach the leachability of heavy metals from sewage sludge, char and ash, municipal solid waste ashes, hazardous waste incinerator fly ashes, power plant ashes and a solidified synthetic waste were assessed. The results indicate that incineration of sewage sludge produces a benign ash with most of the metals speciated as insoluble oxides or silicates. By contrast, incineration of municipal solid waste or hazardous wastes produces fly ashes exhibiting significant metal leachability. Environmentally sensitive metals such as Cd, Zn, Ni and Cu in these fly ashes were readily leachable and probably speciated as water soluble chloride salts. The intrinsic properties approach appears to be an effective method of assessing waste leachability.