Cao Xiangsheng

Nitrite accumulation during wastewater denitrification

Characteristics and mechanisms of nitrite accumulation during wastewater denitrification were reviewed based on our experimental results and literatures reports. Nitrite accumulation may be caused by the rate difference between nitrate reduction and nitrite reduction. It can also is the results of some species of bacteria or enzymes absence in the denitrification sludge. Although literature reports were inconsistency, temperature, dissolved oxygen, pH, types of carbon source and C/N ratios are the main environmental factors that have a big influence on nitrite accumulation. Nitrite is detrimental to aquatic organism if the wastewater containing enough nitrite was discharged to waters or can be a big problem for activated sludge process operation. Nitrite accumulated in denitrification may serve as electron donor for anammox reaction and the demonstration tests are undergoing in our lab.

Experience of ozone-biological aerated filter process in advanced wastewater treatment

an ozone-biological aerated filter process was operated for more than one year to evaluate its feasibility in polishing the secondary effluent of domestic wastewater treatment. The average effluent COD, UV254, color, turbidity, NH3-N were 33.8 mg/L, 0.148 cm−1, 12.6, 1.3 NTU and 6.4 mg/L with the corresponding removal rates 51.9%, 26.6%, 77.2%, 76.4%, 78.0% respectively. Main operational parameters were: ozone dosage 16 mg/L, ozone reaction time 15 min, hydraulic retention time of the biological aerated filter 1 h, ratio of air to water 3∶1.The filtration bed of the biological aerated filter was filled with 1 m high 1∼1.2 mm quartz sand. All results showed excellent performance of the ozone-biological aerated filter process. Experiences proved that the operation parameters such as dosage of ozone should be changed with the influent quality to acquire the best quality of the effluent.

Policies evaluation and recommendation for control of non-point source pollution from agriculture in Chinese Heilongjiang province

Heilongjiang province has the largest area for agriculture in China and its agriculture is a big non-point source for water pollution. The policy reasons of this problem were investigated extensively and recommendations were put forward in this paper. Policy reasons that lead to agriculture as a non-point source of pollution in Heilongjiang province included: unbalance of economy growth and environmental protection in Poverty Alleviation Policy; excessive pollution-produced materials employments stimulated by Agricultural Allowance Policy; negative environmental effects of Family-based Contracted Responsibility Policy; side effect of agricultural structure adjustment during past years. Recommendations to reduce non-point source pollution produced by agriculture were: agricultural structure adjustment under Heilongjiang Ecologic Province Construction Plan; environmental protection infrastructures construction in rural area financed by Chinese New Country Plan; ecological compensation policy, non-point source pollution tax and discharge right transaction foundation in rural areas etc.

Toxicology of Di-(2-ethylhexyl) phthalate in reclaimed wastewater and its removal options

Di-(2-ethylhexyl) phthalate (DEHP) is one of the typical endocrine disrupting chemicals found in water and wastewater. Concentrations of DEHP in water, wastewater and reclaimed wastewater are summarized based on published literatures. Concentrations of DEHP in source water for drinking or final sewage effluents sometimes definitely exceeded legal stipulations for DEHP limits in China. Although physicochemical and biological treatments are the main effective and practical technologies for DEHP removal from water or wastewater, they need further exploration. Novel sustainable treatment technology such as membrane separation processes is essentially needed.