Effect of the addition of organic carbon sources on nitrous oxide emission in anaerobic-aerobic(low dissolved oxygen)sequencing batch reactors

The effect of additional organic carbon sources on the production of nitrous oxide(N_(2)O)in anaerobicaerobic(low dissolved oxygen)real wastewater treatment system was investigated.In this paper,three laboratoryscale sequencing batch reactors(SBRs)(SBR-1,SBR-2 and SBR-3)were operating under an anaerobic-aerobic(low dissolved oxygen,0.15-0.45 mg·L^(-1))configuration.The SBRs were‘long-term cultured’respectively with a single municipal wastewater sample,sodium acetate,and a waste-activated sludge alkaline fermentation liquid as the additional carbon sources of real wastewater.Off-gas analysis showed that N_(2)O was emitted into the atmosphere during the aerobic(low dissolved oxygen)period in the three SBRs,and the order of N_(2)O emission rate was SBR-2>SBR-1>SBR-3.It was observed that the higher poly-β-hydroxyvalerate fraction of polyhydroxyalkanoates,the lower glycogen transformation and less nitrite accumulation was in SBR-3,while the opposite behavior was observed in SBR-2.Further research indicated that the interaction of the factors above potentially affected the N_(2)O emission in the anaerobic-aerobic(low dissolved oxygen)system.

The addition of microbes for treating textile wastewater

Some strains and culture of bacteria which are able to decolorize dyes and degrade polyvinyl alcohol(PVA) were isolated and selected. A pilot scale facultative anaerobic-aerobic biological process was applied for treatment of textile wastewater containing dyes and PVA. Activated carbon adsorption was used as a tertiary treatment stage, and residual sludge from clarifier returned to the anaerobic reactor again. The pilot test were carried out with two systems. One was inoculated by acclimated sludge, and the another was adding the mixed culture of dye-decoloring and PVA-degrading bacteria for forming biological films, the latter was observed to be more effective than the former. The test has run normally for ten months with a COD loading of 2.13 kg/m3/day, a BOD5 loading of 0.34 kg/m3/day in anaerobic reactor; a COD loading of 1.71 kg/m3/day, a BOD5 loading 0.44 kg/m3/day in aerobic reactor. The pollutants removal efficiency by adding microbes was about 20% higher than that by acclimated sludge. The average removal efficiency of COD stood about 92%, BOD5 97%, PVA 90% and decolorization 80%. The other parameters of effluent quality are also satisfactory.

Effects of nitrite on phosphate uptake in anaerobic-oxic process

An anaerobic-oxic(A/O)biological phosphorus removal reactor was operated to study the effect of nitrite on phosphate uptake.The phosphorus uptake profile was determined under different operating conditions.The results indicated that in addition to oxygen and nitrate(DPB_(Na),nitrate denitrifying phosphorus removal),to some extent,nitrite could also serve as an electron acceptor to achieve nitrite denitrifying phosphorus removal(DPB_(Ni)).The quantity and rate of phosphorus uptake of DPBNi,however,were evidently lower than that of DPBNa.The experiment results revealed that nitrite would bring toxic action to phosphate-accumulating organisms(PAOs)when NO_(2)^(−)-Ni93.7 mg/L.The nitrite existing in the anoxic reactor made no difference to the quantity and rate of denitrifying phosphorus removal,but it could reduce the consumption of nitrate.Moreover,the data showed that the aerobic phosphate uptake of DPBNi was lower than that of anaerobic phosphorus-released sludge in a traditional A/O process.However,there was not much difference between these two kinds of sludge in terms of the total phosphorus uptake quantity and the effluent quality.

Advance on the production of polyhydroxyalkanoates by mixed cultures

Polyhydroxyalkanoates(PHAs)are the polymers of hydroxyalkanoates that accumulate as carbon/energy or reducing-power storage material in various microorganisms.PHAs have attracted considerable attention as biodegradable substitutes for conventional polymers.Until now,however,industrial production of PHAs has encountered only limited success.The main barrier to the replacement of synthetic plastics by PHAs has been the higher cost.The use of mixed cultures and renewable sources obtained from waste organic carbon can substantially decrease the cost of PHA and increase their market potential.This work reviews two main methods of PHA production by mixed cultures,anaerobic-aerobic processing and aerobic transient feeding processing,and analyzed the metabolic and effective factors.