Acclimatization of a sequencing batch vertical oxidation pond with simulated agricultural wastewater using duckweed as vegetation: analysis of efficiency, Biomass, and Soil properties.

Vertical oxidation pond operated in sequencing batch mode (HRT: 1.25 day) with duckweed as the vegetation was used to acclimatize with simulated agricultural wastewater. The maximum removal rate of urea [371 g/(m3.d)] and COD [222.4 g/(m3.d)] were observed at moderate concentrations of urea (500 mg/L), N-P-K (60 mg/L), and pesticide (20 mg/L). Inhibition and toxicity posed by higher concentrations, decreased the removals of urea (83% to 61%), COD (81% to 51%), and TDS (76% to 50%) at the end of the acclimatization. Steady removal (> 99%) of PO43--P was observed during acclimatization. Effluent pH increased due to the generation of NH4+-N (maximum 370 ± 5 mg/L) from the assimilation of urea. Oxidation of ammonia led to the maximum generation of NO2--N and NO3--N of 10 mg/L and 9 mg/L, respectively. Particles less than 300 µm increased, and both specific gravity (from 2.62 to 2.42) and maximum dry density (from 1.73 to 1.30 g/cm3) of the base soil decreased with an increase in urea, N-P-K, and pesticide. Reactor biomass increased (1.42 to 1.90 g/L) up to initial concentrations of urea (500 mg/L), N-P-K (60 mg/L), and pesticide (20 mg/L), then decreased (1.68 g/L) with an increase in concentration.

Treatment of petroleum wastewater contaminated with hydrocarbons and inorganics by anoxic-aerobic sequential moving bed reactors.

The present study deals with the biotransformation of virulent petroleum refinery concoction with phenol (750 mg/L), emulsified crude oil (300 mg/L), S2- (750 mg/L), NH4+-N (350 mg/L) and NO3--N (1000 mg/L) in anoxic (A1) - aerobic (A2) moving bed reactors operated in series. The efficacy of the system was analysed through measurement of pollutant concentrations, GC-MS and FTIR peaks of the influent and effluent, and biomass activity studies. The system was able to eliminate the organics and inorganics with more than 99% efficiency at 80 h HRT and 64 h cycle time. GC-MS results revealed breakage of high molecular weight organics to smaller compounds after anoxic treatment. Further treatment of anoxic effluent by aerobic biomass reduced the number of peaks in the final effluent significantly. FTIR results were in accord with the GC-MS results. Heterotrophic activity (HA) of the aerobic biomass was higher than anoxic biomass due to its higher free energy change. Anoxic biomass showed chemolithotrophic activity (CA), suggesting survival in the absence of organics. Gas generated from anoxic reactor consisted of 91% nitrogen, 1% CO2, 1% H2S and rest was unaccounted.

Bioremediation of hydrocarbon containing wastewater in anoxic-aerobic sequential reactors.

Anoxic-aerobic sequential moving-bed reactors were operated for the degradation of synthetic petroleum refinery wastewater containing phenol (750 mg/L), hydrocarbons (1250 mg/L), S2- (750 mg/L), NH4 +-N (350 mg/L), NO3 -N (1000 mg/L) and surfactant as nonylphenol-monoethoxylate (0.2 mmol/L). Kerosene, heavy oil and their mixture were used as hydrocarbon source. Anoxic reactor was a disc-bed reactor and aerobic reactor was moving-bed reactor operated at hydraulic retention times (HRT) of 48 and 16 h respectively at 27 ± 3°C. In anoxic reactor, removals of S2- and NO3 -N were more than 99% along with 50-60% removal of hydrocarbons and phenol. Removal of organics deteriorated in anoxic reactor with heavy oil in feed having higher density and viscosity. Residual organics and NH4 +-N were removed in aerobic reactor with more than 99% efficiency. Biomass activity decreased in anoxic reactor and increased in aerobic reactor with an increase in density and viscosity of hydrocarbon in feed. Abiotic study confirmed most of the removals were due to biodegradation.

Treatment of synthetic refinery wastewater in anoxic-aerobic sequential moving bed reactors and sulphur recovery.

Objective of the present study was to simultaneously biodegrade synthetic petroleum refinery wastewater containing phenol (750 mg/L), sulphide (750 mg/L), hydrocarbon (as emulsified diesel of 300 mg/L), ammonia-nitrogen (350 mg/L) at pH >9 in anoxic-aerobic sequential moving bed reactors. The optimum mixing speed of anoxic reactor was observed at 20 rpm and beyond that, removal rate remained constant. In anoxic reactor the minimum hydraulic retention time was observed to be 2 days for complete removal of sulphide, 40-50% removal of phenol and total hydrocarbons and 52% of sulphur recovery. The optimum HRT of aerobic moving bed reactor was observed as 16 h (total HRT of 64 h for anoxic and aerobic reactors) for complete removals of phenol, total hydrocarbons, COD (chemical oxygen demand) and ammonia-nitrogen with nitrification.