A combined biologic and chemical treatment of high-strength (total chemical oxygen demand [CODtoJ up to 20 g/L), strong nitrogenous (totalNup to 1 g/L), and phosphoric (total P up to 0.4 g/L) starch industry wastewater was investigated at laboratory-scale level. As a principal step for COD elimination, upflow anaerobic sludge bed reactor performance was investigated at 30°C. Under hydraulic retention times (HRTs) of about 1 d, when the organic loading rates were higher than 15 g of COD / (L.d), the CODtot removal varied between 77 and 93%, giving effluents with a COD/N ratio of 4-5:1, approaching the requirements of subsequent denitrification. The activated sludge reactor operating in aerobic-anoxic regime (HRT of about 4 d, duration of aerobic and anoxic phases of 30 min each) was able to remove up to 90% of total nitrogen and up to 64% of COD tot from the anaerobic effluents under 17-20°C. The coagulation experiments with Fe (III) showed that 1.4mg of resting hardly biodegradable COD and 0.5 mg of phosphate (as P) could be removed from the aerobic effluents by each milligram of iron added.

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This work demonstrates a possibility of composting of municipal waste waters sludge (WWS) digested during 5-7 days, of the Kuryanovo waste water treatment plants (the city of Moscow) without the use of traditional organic additives – sawdust, peat, thatch. As a recycling filler (repeatedly used), enhancing the porosity of the composted mixture, ribbed polyethylene spheres (∅=8 cm) and wood chips (having dimension of 5-10 cm) were used. Composting was performed efficiently in both cases, however, the use of wood ships had technological and economical advantages. The process of composting was carried out during 2-4 weeks and was composed of classical phases of active heating (a rate of 0.2-0.3oC/h was obtained), maintaining of maximum temperature during 1-2 days, and cooling down to the ambient temperature. During the course of composting, a product was obtained, having attractive organoleptic properties, suitable for application in municipal laying-out of greenery.

Aerobic biological treatment of digested sludge was studied in a continuously operated laboratory set-up. An aerated reactor was filled with thermophilically digested sludge from the Moscow wastewater treatment plant and inoculated with special activated sludge. It was then operated at the chemostat mode at different flow rates. Processes of nitrification and denitrification, as well as dephosphatation, occurred simultaneously during biological aerobic treatment of thermophilically digested sludge. Under optimal conditions, organic matter degradation was 9.6%, the concentrations of ammonium nitrogen and phosphate decreased by 89 and 83%, respectively, while COD decreased by 12%. Dewaterability of digested sludge improved significantly. The processes were found to depend on hydraulic retention time, oxygen regime, and temperature. The optimal conditions were as follows: hydraulic retention time 3-4 days, temperature 30-35 degrees C, dissolved oxygen levels 0.2-0.5 mg/L at continuous aeration or 0.7-1 mg/L at intermittent aeration. Based on these findings, we propose a new combined technology of wastewater sludge treatment. The technology combines two stages: anaerobic digestion followed by aerobic biological treatment of digested sludge. The proposed technology makes it possible to degrade the sludge with conversion of approximately 45% volatile suspended solids to biogas, to improve nitrogen and phosphorus removal in reject water from sludge treatment units, and to achieve removal of malodorous substances after 8-9 days of anaerobic-aerobic sludge treatment.