A batch respirometric test was developed to measure the response of activated sludge communities degrading low concentrations of organic chemicals. The low substrate concentrations used in the assay ensure that minimal changes occur in the physiological state of the degrading community. The estimated kinetic parameters are, therefore, extant, that is, representative of the existing condition of the biomass in the continuous bioreactor. Monte Carlo and sensitivity analyses were performed to verify the robustness of the technique for determining unique and accurate estimates of the parameters describing Monod and Andrews kinetics. Application of the technique to a laboratory‐scale activated sludge system showed that kinetic parameter estimates were reproducible and independent of the substrate concentration within the range tested (0.2–4.0 mg/L as chemical oxygen demand [COD]). Low Ks values (<0.1 mg/L as COD) were measured by the assay for the biodegradation of phenol and 4‐chlorophenol, both of which exhibited an inhibitory response (Andrews kinetics). The biodegradation of ethylene glycol, acrylamide, and acetate exhibited Monod kinetics.

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Geochemical equilibrium speciation modeling was used to determine optimum conditions for precipitation of magnesium ammonium phosphate, or struvite, for the recovery of nutrients from anaerobically digested wastes. Despite a wide range of pH values with the potential to precipitate struvite, the optimum pH was determined to be 9.0. Bench experiments conducted on effluent from an anaerobic sequencing batch reactor (ASBR) treating swine wastes achieved a maximum of 88% ammonia removal at a pH of 9.5 with added magnesium and phosphate to achieve an ammonium: magnesium: phosphate molar ratio of 1:1.25:1. Struvite precipitation was performed on a continuous basis in a pilot-scale ASBR treating swine wastes. Through the addition of supplemental magnesium and phosphate, the ammonia concentration was reduced from 1500 mg/L as nitrogen to less than 10 mg/L. The supenatant from the struvite precipitation clarifier was recycled to the feed of the ASBR without adverse impact, simulating on-farm effluent reuse as flush water.

Anaerobic treatment of dilute wastewater was studied using three laboratory‐scale anaerobic sequencing batch reactors (ASBRs), each with an active volume of 6 L. The reactors were fed a synthetic substrate made from nonfat dry milk supplemented with nutrients and trace metals. The chemical oxygen demand (COD) and 5‐day biochemical oxygen demand (BOD5) of the feed were 600 mg/L and 285 mg/L, respectively. Steady‐state performance data were collected over a time period of 2 years at reactor temperatures of 5, 7.5, 10, 12.5, 15, 17.5, 20, and 25°C. Hydraulic retention times (HRTs) were maintained at 24, 16, 12, 8, and 6 hours. Steady‐state process kinetics and removal efficiencies were evaluated for the various conditions. Results showed that the ASBR process was capable of achieving more than 90% soluble COD (SCOD) and BOD5, removal at temperatures of 20°C and 25°C at all HRTs. At a temperature of 5°C and a 6‐hour HRT, SCOD and BOD5, removals were 62% and 75%, respectively. At intermediate temperatures ranging from 5 to 25°C and HRTs between 24 and 6 hours, removal of soluble organic matter ranged from 62 to 90% for COD and from 75 to 90% for BOD5. In all cases, solids retention times were high enough to maintain good performance. Substrate removal rates and half‐saturation coefficients were also determined at all temperatures. The temperature correction coefficient was determined to be 1.08 in the temperature range of 7.5 to 25°C. It is concluded that the ASBR has unique characteristics that enable efficient removal of organics during treatment of dilute wastewaters at low temperatures.

The performance and operational stability of a pilot-scale static granular bed reactor (SGBR) for the treatment of dairy processing wastewater were investigated under a wide range of organic and hydraulic loading rates and temperature conditions. The SGBR achieved average chemical oxygen demand (COD), biological oxygen demand (BOD), and total suspended solids (TSS)-removal efficiencies higher than 90% even at high loading rates up to 7.3 kg COD/m(3)/day, with an hydraulic retention time (HRT) of 9 h, and at low temperatures of 11 °C. The average methane yield of 0.26 L CH4/g COD(removed) was possibly affected by a high fraction of particulate COD and operation at low temperatures. The COD mass balance indicated that soluble COD was responsible for most of the methane production. The reactor showed the capacity of the methanogens to maintain their activity and withstand organic and hydraulic shock loads.