James W. Atwater

Experiments using Daphnia to measure landfill leachate toxicity

Abstract Leachate from municipal refuse was analysed for acute toxicity using Daphnia pulex, rainbow trout (Salmo gairdneri) and sockeye salmon (Oncorhynchus nerka) as test organisms. Procedures used in conducting the daphnia bioassay are detailed. The 3 1 2 - year testing program was designed to compare daphnia bioassays with standard fish bioassays and residual oxygen bioassays (ROB). The results from the daphnia bioassays compared favourably with the standard fish bioassay results. No disadvantages could be seen in using daphnia rather than fish as test organisms for determining the acute toxicity of municipal refuse leachates. However, both financial and logistic advantages could be gained by using daphnia rather than fish.

Recovery of phosphorus from dairy manure: a pilot-scale study

Phosphorus was recovered from dairy manure via a microwave-enhanced advanced oxidation process (MW/H2O2-AOP) followed by struvite crystallization in a pilot-scale continuous flow operation. Soluble phosphorus in dairy manure increased by over 50% after the MW/H2O2-AOP, and the settleability of suspended solids was greatly improved. More than 50% of clear supernatant was obtained after microwave treatment, and the maximum volume of supernatant was obtained at a hydrogen peroxide dosage of 0.3% and pH 3.5. By adding oxalic acid into the supernatant, about 90% of calcium was removed, while more than 90% of magnesium was retained. As a result, the resulting solution was well suited for struvite crystallization. Nearly 95% of phosphorus in the treated supernatant was removed and recovered as struvite.

Groundwater nitrate profiling by passive sampling over extended depth beneath the water table: A demonstration

Abstract A multi-layer sampler, developed on the basis of a previously described dialysis membrane technique, was used to passively sample groundwater nitrate (NO 3 ) in two unconfined aquifers. Monthly sampling performed over a 3 month period at each location has shown the feasibility of using this technique over extended depth, and that it can provide a detailed and highly repeatable characterization of the groundwater chemical profiles.

A case study of nuisance impact screening for municipal waste landfill planning

Abstract Nuisance impacts from waste facilities can aggravate community resistance because odor, noise and visual impacts trigger more serious concerns about impacts on community health, image and property values (1). In order to assess nuisances, initial site selection processes for municipal landfills should use screening models to determine potential nuisance impact zones. Predicted impact zones could provide a basis to plan buffer zones and mitigation efforts. This research work identifies simple screening models and required data to predict air quality, odors, noise and visual impacts. The predicted results are compared with measured values for odors, noise and visual impacts at a landfill that exhibits typical characteristics of the landfills in Western Canada, Washington and Oregon. The results show that simple predictive methods fairly accurately describe the facilitys nuisance footprint. Landfill gas migration and dispersion affect odors up to 500 m downwind and may serve as indicators for poten...

The role of soil humic and fulvic acid in the sorption of endosulfan (alpha and beta)

The sorption behaviour of alpha- and beta-endosulfan in soil organic matter was investigated using standard soil humic acid (HA) and soil fulvic acid (FA) with a modified solubility enhancement method and a dialysis bag technique. For HA, all the experiments were conducted at an ionic strength of 0.001 mol/L, in both the presence and absence of calcium and at an ionic strength of 0.01 mol/L. For FA, the experiments were conducted at two ionic strengths: 0.001 mol/L (with calcium) and 0.01 mol/L. This study is the first to describe the striking differences in the sorption behaviours of the two stereoisomers of endosulfan in HA and in FA. The sorption coefficients of alpha-endosulfan in HA and FA were significantly higher than those of beta-endosulfan. Beta-endosulfan has comparable sorption coefficients (1.5–5.4 L/g) in HA and in FA. Ionic strength and the presence of calcium have no significant effect on the sorption of beta-endosulfan in HA. However, calcium can significantly (p=0.01) enhance the solubility of alpha-endosulfan in HA. Changes in ionic strength by one order of magnitude also affect the solubility of alpha-endosulfan in HA. The sorption coefficients of alpha-endosulfan in HA (10–36 L/g) were greater than those in FA (9–14 L/g). The chirality of the alpha-isomer was hypothesised to be the primary reason behind its higher sorption in soil organic matter relative to the beta-isomer. In the presence of dissolved HA and FA found in natural soil environments, solubility of endosulfan can be increased by five times than the aqueous solubility of endosulfan without HA and FA.

Sorption of endosulphan sulphate in soil organic matter

Sorption of endosulphan sulphate in soil organic matter was investigated using Standard Elliot soil humic acid (HA) and soil fulvic acid (FA) at two ionic strengths (0.001 and 0.01). It was observed that divalent calcium ion and ionic strength affect the sorption of endosulphan sulphate in HA. All the experiments were carried out at pH 6.7±0.1. In the presence and absence of calcium (ionic strength 0.001), the solubility enhancement method was used to estimate the sorption coefficients of endosulphan sulphate in HA. For FA, the solubility enhancement method was used to estimate the sorption coefficients at an ionic strength of 0.001 (in the presence of calcium) and 0.01. The presence of calcium was found to significantly enhance (α=0.01) the solubility of endosulphan sulphate in HA. Sorption coefficients at pH 6.7, obtained using the solubility enhancement method, were found to be 10–21 L/g in HA and 6 L/g in FA (in the presence of calcium). Increase in ionic strength from 0.001 to 0.01 decreased the sorption of endosulphan sulphate in HA. The effect of ionic strength and calcium on the sorption of endosulphan sulphate was most satisfactorily explained on the basis of the Donnan volume.