In order to improve the nitrogen removal efficiency and save operational cost,the feasibility of the alternating aerobic-anoxic process(AAA process)applied in a sequencing batch reactor(SBR)system for nitrogen removal...In order to improve the nitrogen removal efficiency and save operational cost,the feasibility of the alternating aerobic-anoxic process(AAA process)applied in a sequencing batch reactor(SBR)system for nitrogen removal was investigated.Under sufficient influent alkalinity,the AAA process did not have an advantage over one aerobic-anoxic(OAA)cycle on treatment efficiency because microorganisms had an adaptive stage at the alternating aerobic-anoxic transition,which would prolong the total cycling time.On the contrary,the AAA process made the system control more complicated.Under deficient influent alkalinity,when compared to OAA,the AAA process improved treatment efficiency and effluent quality with NH4+-N in the effluent below the detection limit.In the nitrification,the average stoichiometric ratio between alka-linity consumption and ammonia oxidation is calculated to be 7.07 mg CaCO_(3)/mg NH4+-N.In the denitrification,the aver-age stoichiometric ratio between alkalinity production and N_(3)^(−)-N reduction is about 3.57 mg CaCO(3)/mg NO_(3)^(−)-N.As a result,half of the alkalinity previously consumed during the aerobic nitrification was recovered during the subsequent anoxic denitrification period.That was why the higher treat-ment efficiency in the AAA process was achieved without the supplement of bicarbonate alkalinity.If the lack of alkalinity in the influent was less than 1/3 of that needed,there is no need for external alkalinity addition and treatment efficiency was the same as that under sufficient influent alkalinity.Even if the lack of alkalinity in the influent was more than 1/3 of that needed,the AAA process was an optimal strategy because it reduced the external alkalinity addition and saved on operational cost.展开更多
Selenium (Se)-containing industrial wastewater is often coupled with notable salinity. However, limited studies have examined biological treatment of Se-containing wastewater under high salinity conditions. In this st...Selenium (Se)-containing industrial wastewater is often coupled with notable salinity. However, limited studies have examined biological treatment of Se-containing wastewater under high salinity conditions. In this study, a sequencing batch reactor (SBR) inoculated with activated sludge was applied to treat selenate in synthetic saline wastewater (3% w/v NaCl) supplemented with lactate as the carbon source. Start-up of the SBR was performed with addition of 1–5 mM of selenate under oxygen-limiting conditions, which succeeded in removing more than 99% of the soluble Se. Then, the treatment of 1 mM Se with cycle duration of 3 days was carried out under alternating anoxic/oxic conditions by adding aeration period after oxygen-limiting period. Although the SBR maintained soluble Se removal of above 97%, considerable amount of solid Se remained in the effluent as suspended solids and total Se removal fluctuated between about 40 and 80%. Surprisingly, the mass balance calculation found a considerable decrease of Se accumulated in the SBR when the aeration period was prolonged to 7 h, indicating very efficient Se biovolatilization. Furthermore, microbial community analysis suggested that various Se-reducing bacteria coordinately contributed to the removal of Se in the SBR and main contributors varied depending on the operational conditions. This study will offer implications for practical biological treatment of selenium in saline wastewater.展开更多
The characteristic of phosphorus removal andappropriate change of the traditional operation modes wereinvestigated in UniFed sequencing batch reactor (SBR)laboratory-scale apparatus (40 L), treating actual domesticwas...The characteristic of phosphorus removal andappropriate change of the traditional operation modes wereinvestigated in UniFed sequencing batch reactor (SBR)laboratory-scale apparatus (40 L), treating actual domesticwastewater with low ratios of C/N (2.57) and C/P (30.18),providing theoretical basis for actual application ofwastewater treatment plant. UniFed SBR system with itsunique operation mode had the distinct superiority ofphosphorus removal. On this occasion, the effect ofvolumetric exchange ratio (VER) and the method ofinfluent introduction for phosphorus removal were studied.When the carbon source became the limiting factor tophosphorus release, the higher the VER, the lower thephosphorus concentration in the effluent. Three differentinfluent patterns, including one-time filling, four-timefilling, and continuous filling with the same quantity ofwastewater could increase the release rate of anaerobicphosphorus from 0.082 to 0.143 mg·P·(L·min)-1. Appropriatechange of the traditional operation modes couldoptimize the efficiency of phosphorus removal. When thefeed/ decant time was extended from 2 h to 4 h, thephosphorous removal efficiency increased from 59.93% to88.45% without any external carbon source. In the mode ofalternation of anoxic-aerobic (A/O) condition, phosphorousremoval efficiency increased from 55.07% to 72.27%clearly. The carbon source in the influent can be usedadequately, and denitrifying phosphorus removal wascarried out in anoxic stage 2 (A2). This mode was optimalfor the treatment of actual domestic wastewater with lowC/N and C/P ratios.展开更多
基金This work was supported by the National Nature Science Foundation of China(Grant No.50608001)Beijing Education Committee(Grant No.KM200710005014).
文摘In order to improve the nitrogen removal efficiency and save operational cost,the feasibility of the alternating aerobic-anoxic process(AAA process)applied in a sequencing batch reactor(SBR)system for nitrogen removal was investigated.Under sufficient influent alkalinity,the AAA process did not have an advantage over one aerobic-anoxic(OAA)cycle on treatment efficiency because microorganisms had an adaptive stage at the alternating aerobic-anoxic transition,which would prolong the total cycling time.On the contrary,the AAA process made the system control more complicated.Under deficient influent alkalinity,when compared to OAA,the AAA process improved treatment efficiency and effluent quality with NH4+-N in the effluent below the detection limit.In the nitrification,the average stoichiometric ratio between alka-linity consumption and ammonia oxidation is calculated to be 7.07 mg CaCO_(3)/mg NH4+-N.In the denitrification,the aver-age stoichiometric ratio between alkalinity production and N_(3)^(−)-N reduction is about 3.57 mg CaCO(3)/mg NO_(3)^(−)-N.As a result,half of the alkalinity previously consumed during the aerobic nitrification was recovered during the subsequent anoxic denitrification period.That was why the higher treat-ment efficiency in the AAA process was achieved without the supplement of bicarbonate alkalinity.If the lack of alkalinity in the influent was less than 1/3 of that needed,there is no need for external alkalinity addition and treatment efficiency was the same as that under sufficient influent alkalinity.Even if the lack of alkalinity in the influent was more than 1/3 of that needed,the AAA process was an optimal strategy because it reduced the external alkalinity addition and saved on operational cost.
文摘Selenium (Se)-containing industrial wastewater is often coupled with notable salinity. However, limited studies have examined biological treatment of Se-containing wastewater under high salinity conditions. In this study, a sequencing batch reactor (SBR) inoculated with activated sludge was applied to treat selenate in synthetic saline wastewater (3% w/v NaCl) supplemented with lactate as the carbon source. Start-up of the SBR was performed with addition of 1–5 mM of selenate under oxygen-limiting conditions, which succeeded in removing more than 99% of the soluble Se. Then, the treatment of 1 mM Se with cycle duration of 3 days was carried out under alternating anoxic/oxic conditions by adding aeration period after oxygen-limiting period. Although the SBR maintained soluble Se removal of above 97%, considerable amount of solid Se remained in the effluent as suspended solids and total Se removal fluctuated between about 40 and 80%. Surprisingly, the mass balance calculation found a considerable decrease of Se accumulated in the SBR when the aeration period was prolonged to 7 h, indicating very efficient Se biovolatilization. Furthermore, microbial community analysis suggested that various Se-reducing bacteria coordinately contributed to the removal of Se in the SBR and main contributors varied depending on the operational conditions. This study will offer implications for practical biological treatment of selenium in saline wastewater.
基金This work was supported by the Joint Research Fund for Overseas Natural Science Foundation of China(Grant No.50628808)State Key Laboratory of Urban Water Resource and Environment(HIT)(No.QAK200802)Academic Human Resources Development in Institutions of Higher Learning Under the Jurisdiction of Beijing Municipality(No.PHR20090502)。
文摘The characteristic of phosphorus removal andappropriate change of the traditional operation modes wereinvestigated in UniFed sequencing batch reactor (SBR)laboratory-scale apparatus (40 L), treating actual domesticwastewater with low ratios of C/N (2.57) and C/P (30.18),providing theoretical basis for actual application ofwastewater treatment plant. UniFed SBR system with itsunique operation mode had the distinct superiority ofphosphorus removal. On this occasion, the effect ofvolumetric exchange ratio (VER) and the method ofinfluent introduction for phosphorus removal were studied.When the carbon source became the limiting factor tophosphorus release, the higher the VER, the lower thephosphorus concentration in the effluent. Three differentinfluent patterns, including one-time filling, four-timefilling, and continuous filling with the same quantity ofwastewater could increase the release rate of anaerobicphosphorus from 0.082 to 0.143 mg·P·(L·min)-1. Appropriatechange of the traditional operation modes couldoptimize the efficiency of phosphorus removal. When thefeed/ decant time was extended from 2 h to 4 h, thephosphorous removal efficiency increased from 59.93% to88.45% without any external carbon source. In the mode ofalternation of anoxic-aerobic (A/O) condition, phosphorousremoval efficiency increased from 55.07% to 72.27%clearly. The carbon source in the influent can be usedadequately, and denitrifying phosphorus removal wascarried out in anoxic stage 2 (A2). This mode was optimalfor the treatment of actual domestic wastewater with lowC/N and C/P ratios.
