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Effect of nitrate concentration on filamentous bulking under low level of dissolved oxygen in an airlift inner circular anoxic-aerobic incorporate reactor

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Journal of Environmental Sciences 2013年第9期25卷 1736-1744页

作者： Yiming Su Yalei Zhang Xuefei Zhou Ming Jiang State Key Laboratory of Pollution Control and Resource Reuse Tongji University

This laboratory research investigated a possible cause of filamentous bulking under low level of dissolved oxygen conditions （dissolved oxygen value in aerobic zone maintained between 0.6-0.8 mgO2 /L） in an airlift inner-circular anoxic-aerobic reactor. During the operating period, it was observed that low nitrate concentrations affected sludge volume index significantly. Unlike the existing hypothesis, the batch tests indicated that filamentous bacteria （mainly Thiothrix sp.） could store nitrate temporarily under carbon restricted conditions. When nitrate concentration was below 4 mg/L, low levels of carbon substrates and dissolved oxygen in the aerobic zone stimulated the nitrate-storing capacity of filaments. When filamentous bacteria riched in nitrate reached the anoxic zone, where they were exposed to high levels of carbon but limited nitrate, they underwent denitrification. However, when nonfilamentous bacteria were exposed to similar conditions, denitrification was restrained due to their intrinsic nitrate limitation. Hence, in order to avoid filamentous bulking, the nitrate concentration in the return sludge （from aerobic zone to the anoxic zone） should be above 4 mg/L, or alternatively, the nitrate load in the anoxic zone should be kept at levels above 2.7 mg NO-3N/g SS.

关键词： anoxic-aerobic system low dissolved oxygen filamentous bulking low nitrate concentration nitrate-storing capacity

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Macrobenthic assemblages of the Changjiang River estuary (Yangtze River, China) and adjacent continental shelf relative to mild summer hypoxia

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Chinese Journal of Oceanology and Limnology 2017年第3期35卷 481-488页

作者：廖一波寿鹿汤雁滨曾江宁高爱根陈全震严小军 Key Laboratory of Marine Ecosystem and Biogeochemistry Second Institute of OceanographyState Oceanic Administration Key Laboratory of Applied Marine Biotechnology Ministry of Education Marine College of Ningbo University

To assess the effects of hypoxia, macrobenthic communities along an estuarine gradient of the Changjiang estuary and adjacent continental shelf were analyzed. This revealed spatial variations in the communities and relationships with environmental variables during periods of reduced dissolved oxygen （DO） concentration in summer. Statistical analyses revealed significant differences in macrobenthic community composition among the three zones： estuarine zone （EZ）, mildly hypoxic zone （MHZ） in the continental shelf, and norrnoxic zone （NZ） in the continental shelf（Global R=0.206, P=0.002）. Pairwise tests showed that the macrobenthic community composition of the EZ was significantly different from the MHZ （pairwise test R=0.305, P=0.001） and the NZ （pairwise test R=0.259, P=-0.001）. There was no significant difference in macrobenthic communities between the MHZ and the NZ （pairwise test R=0.062, P=-0.114）. The taxa included small and typically opportunistic polychaetes, which made the greatest contribution to the dissimilarity between the zones. The effects of mild hypoxia on the macrobenthic communities are a result not only of reduced DO concentration but also of differences in environmental variables such as temperature, salinity, and nutrient concentrations caused by stratification.

关键词： hypoxia macrobenthos benthic community Changjiang estuary low dissolved oxygen

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Combined process of sequencing batch reactor activated sludge process and constructed wetland for domestic wastewater treatment

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Journal of Chongqing University 2010年第4期9卷 201-207页

作者：魏武强 Wisaam S. Al-Rekabi Environment Engineering Research and Design Department China Railway Siyuan Survey and Design Group Co. Ltd Key Laboratory of Eco-environments in Three Gorges Reservoir Region Ministry of Education Civil Engineering Department College of Engineering Basra University

By combining sequencing batch reactor (SBR) activated sludge process and constructed wetland (CW), this study is to achieve the domestic wastewater treatment. Our purpose was to determine the optimum operating parameters of the combined process. The process involved advantages and shortages of SBR and CW. Under normal temperature, the 3rd cycle (SBR’s operation cycle is 8 h: inflow for 1 h, limited aeration for 3 h, sediment for 1 h, outflow for 1 h, and idling for 2 h; CW’s hydraulic retention time (HRT) is 24.8 h and hydraulic loading is 24.5 m3/m2 d) was the best cyclic mode. The effluents can meet the standard GB/T18921-2002: "The reuse of urban recycling water: water quality standard for scenic environment use". In the 3rd cycle, the efficiency of CW was the maximum, and energy consumption of SBR was the minimum. Under the condition of low dissolved oxygen, the removing efficiency of chemical oxygen demand (COD) and ammonia was not affected obviously. Simultaneously, nitrification and denitrification phenomena occured and phosphorus was absorbed obviously.

关键词： sequencing batch reactor activated sludge process constructed wetland energy consumption low dissolved oxygen

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