Syed R. Qasim

Computer Simulation of Leachate Quality by Recirculation in a Sanitary Landfill Bioreactor

Abstract Sanitary Landfills are the most widely used method of solid waste disposal around the world. Modern sanitary landfills are designed with impervious liners, and leachate collection, removal, and treatment systems to minimize the potential for groundwater contamination. Leachate recycle through the landfill is an effective method of leachate treatment, and to enhance solid waste stabilization. A mathematical model is developed to simulate the release of contaminants from solid wastes, and their movement into the percolating liquid. Two differential equations are used that express the mass balance of the contaminants in the percolating water and those in the solid wastes. These simultaneous linear differential equations are solved numerically using a fourth-order Runge-Kutta algorithm with many physical and process parameters. The model results are used to estimate the active life of landfill with and without leachate recirculation. Such information is valuable in the operation, maintenance, and closure plan of a sanitary landfill.

Photocatalytic reactivity of thallium(I) species in aqueous suspensions of titania

Abstract The reactivity of Tl(I) species in UV-irradiated TiO 2 suspensions is described. It is shown that the reaction pathway undergone by these species depends crucially on the conditions extant in these media. The Tl(I) conversion pathway switches from a reductive one in organic additive-containing suspensions to an oxidative one in the O 2 -containing media. Thus the influence of organic or inorganic co-additives, the purged gas (whether Ar or O 2 ), and platinization of the TiO 2 surface, on the extant of initial (dark) adsorption of Tl(I) on the TiO 2 surface, and on the initial product of the photoreaction, is described.

Treatment of domestic sewage by using solar distillation and plant culture

Abstract A solar‐still‐greenhouse system was investigated for treatment of sewage, recovery of high quality distillate, and to utilize the nutrients contained in sewage for plant culture. Two small solar‐still‐greenhouses were constructed and operated. The temperature variation in the solar stills and greenhouses, distillate condensation rate and its quality and plant viability in both units were investigated. The results indicate that solar radiation deodorizes sewage and reduces its BOD in the still. Condensates were free of coliform organisms, contained ammonia nitrogen and BOD in small concentrations.

Adsorption of thallium(I) ions on titania particle surfaces in aqueous media

A description is given of the modification of the adsorption of Tl(I) on a titania (Degussa P-25) surface by the presence of organic or inorganic co-additives in aqueous suspensions. The addition of oxalate, formate, acetate and phosphate anions (the latter at low levels below ~0.03 M) increased Tl(I) adsorption while the phosphate anion (at levels > ~0.03 M) inhibited Tl(I) adsorption. A surface complexation model comprising the titania surface sites, the anchor co-additives and bound Tl(I) species was invoked to explain the adsorption enhancement observed. The data presented build upon and complement those acquired earlier showing how metal ion adsorption on a TiO2 surface is strongly influenced by co-additives in the aqueous medium.

Metal toxicity evaluation using bioassay and microtox

The heavy metals cadmium, copper, lead, silver, nickel and zinc were evaluated for acute toxicity concentrations using bioassay with Daphnia magna (D. magna) and Photo‐bacterium phosphoreum (P. phosphoreum) using Microtox™ toxicity test apparatus. Synthetic chelating agents Ethylenediaminetetraacetic acid (EDTA) and Nitrilotriacetic acid (NTA) were used for reduction of heavy metal toxicity. Copper, lead, silver were highly toxic to D. magna. Cadmium and nickel exhibited very low toxicity to P. phosphoreum. EDTA and NTA were effective in reducing metal toxicity to both organisms. However, the toxicity reduction to D. magna was significantly higher than that to P. phosphoreum.

Biological nutrient removal in anoxic‐anaerobic‐aerobic treatment process

A suspended growth biological nutrient removal process was designed and operated to achieve high removal of organics, nitrogen and phosphorus from wastewater without the addition of chemicals. The process utilized anoxic, anaerobic and aerobic reactor sequences with sludge return. A bench‐scale unit was operated in the laboratory. The biological kinetic coefficients for removal of BOD5 were developed by varying the mean cell residence time. This was achieved by operating the reactors at six different MLSS concentrations, 5000, 4200, 3300, 2600, 1900, and 1200 mg/L. This process eliminated the need for an internal recycle; and total detention time for three reactors was less than that for conventional activated sludge.

Laboratory investigations to address the use of compost amendments to enhance expansive subsoils

The process of composting of organic wastes is expanding rapidly in the United States and other countries since landfill spaces or disposal of organic wastes are becoming scarce and expensive. Compost materials, given their moisture affinity and low hydraulic conductivity, can provide stabilization of natural expansive soils by mitigating shrinkage cracking and encapsulating subsoil surfaces. To verify these advantages, a research study was conducted to measure the geotechnical characteristics of composts and compost treated topsoils (CMTs). Two types of composts, Dairy Manure and Biosolids, and a local expansive soil were used as materials. This paper presents laboratory test results from Atterberg, organic content, direct shear strength, free swell, linear shrinkage, and hydraulic conductivity tests and analyses of these results to evaluate the potential applications of CMTs to serve as highway shoulder covers to mitigate shrinkage cracks. The results indicate that shrinkage strains are reduced and strength and swell strains are increased with the use of compost amendments. Environmental assessments including the presence of organic matter are also addressed.

Methane Gas Production from Anaerobic Digestion of Cattle Manure

Abstract Abstract Methane gas generation from organic wastes is being looked upon today as a potential energy source. A study was conducted to develop biological kinetic coefficients for anaerobic digestion of animal wastes. A bench-scale anaerobic digester and gas collection system was constructed. Ground and screened cattle manure from grain-fed animals was used for development of kinetic coefficients. Measurements of pH, alkalinity, total solids, suspended solids and volatile solids, and total and dissolved COD were taken for the feed and for the effluent. The biological reaction rate constants and gas production rate for cattle manure were developed. These constants compare well with those for other wastes.

Enhanced nutrient removal by biological treatment systems

The importance of nitrogen and phosphorus in stimulating eutrophic conditions in receiving waters has been well documented. As a result, over the last decade an increased emphasis has been placed on limiting these elements in wastewater effluents. In the future, new discharge permits will include limits on both of these elements. In 1985 a research program was initiated to conduct a pilot plant study of an anoxic/anaerobic/aerobic treatment train using primary effluent. The facility was operated at varying flow and Qr/Q ratios, and at effective mixed liquor suspended solids (MLSS) concentrations of 3100 mg/L. The results of the first 13 month operational phase indicated that the effluent concentrations of total BOD5, TSS and nitrate nitrogen were less than 5 mg/L. Ammonia nitrogen was less than 0.2 mg/L. The solids settleability was excellent, and foaming due to Norcadia, was effectively controlled. The average overall phosphorus removal was 48%. Influent BOD5 concentrations of less than 100 mg/L signific...

Experimental investigations to evaluate benefits of using compost amendments to modify expansive soils

Composting is a successful method of recycling organic waste materials such as yard trimmings, municipal biosolids, animal manure and organic urban wastes into stabilised materials that could be used for bioremediation, erosion control, landscaping, and roadside vegetation. The process of organic wastes composting is expanding rapidly in the USA and other countries since landfill spaces for disposal of organic wastes are becoming scarce and expensive. Researchers and practitioners always seek new application areas for composts. Compost materials, given their moisture affinity (hydrophilic characteristics) and low permeability characteristics, could provide stabilisation of natural expansive subgrades by mitigating shrinkage cracking and encapsulating subsoil surfaces. In order to verify these advantages, a research study was conducted to measure geotechnical characteristics of composts and Compost-Treated Topsoils (CMTs). Two types of composts, dairy manure and biosolids, and a local expansive soil were studied. This paper presents the laboratory test results, which showed that compost amendments resulted in the reductions of linear shrinkage strains and increase of shear strength and swell strains. Ranking analyses of test results also showed that compost amendments provided low to moderate enhancements to subsoil properties. Currently, field studies are being conducted to address potential applications of CMTs as unpaved shoulder covers to encapsulate and maintain compaction moisture conditions.