Pilot-scale studies of domestic wastewater treatment by typical constructed wetlands and their greenhouse gas emissions

Three typical constructed wetlands(CWs)including Vertical Flow(VF),Free Water Surface(FWS),and Subsurface Flow(SF),and combined VF-SF-FWS constructed wetlands were investigated for the treatment of domestic wastewater with low C/N ratio.The performance of nutrient removal and the characteristics of greenhouse gas emissions,such as CH4 and N2O,from these CWs were compared.The results indicated that the four types of CWs had high removal efficiencies for organic matter and suspended solid(SS).The combined wetland also showed a comparatively good performance for nitrogen and phosphorus removal,and the removal efficiencies for total nitrogen(TN)and total phosphorus(TP)were 81.3%and 84.5%,respectively.The combined CWs had a comparative lower global warming potential.The FWS CW had the highest tendency to emit CH4 and led to a higher global warming potential among the four types of CWs,which was about 586 mg CO_(2)/m^(2)·h.

水温和C/N对土地生物过滤处理系统氮去除的影响

在流量为40 L/d、回流比为200%的条件下,以碎石为填料,结合小试实验研究了温度和COD/NH4+-N(C/N)对AO型污水土地生物过滤处理系统,处理人工生活污水中氮的影响。实验结果表明,随水温和C/N的升高,首先系统对NH4+-N的去除率先增大后减小,当水温为7.3℃、C/N为5时,系统对NH4+-N的去除率最高,达到了91.1%;其次系统反硝化率逐渐升高,当水温为8.2℃、C/N为6时,反硝化率达到了95.4%;此外,系统中硝化反硝化作用受到影响,导致对TN的去除率先增大后减小,当水温为8.2℃、C/N为6时,系统对TN的去除率达到49.91%。在厌氧阶段,系统TN的去除主要靠反硝化作用将硝酸盐氮脱除,并且存在中间产物积累;进入好氧阶段,系统通过硝化作用将氨氮转化为硝酸盐氮,只是氮素形态的转化,并未从系统中脱氮。

广州萝岗中心区水质净化厂节地设计案例

广州萝岗中心区水质净化厂首期工程设计规模为5×104 m^(3)/d,设计出水水质执行GB 18919—2002一级A标准和广东省标准《水污染排放限值》(DB 44/26—2001)第二时段城镇二级污水处理厂一级标准。工程用地面积有限,采用间歇式活性污泥(CAST)生物处理工艺+高效沉淀池+高效纤维滤池的处理工艺,尾水采用紫外线消毒。CAST池主反应区停留时间确定为18 h,高效纤维滤池设计滤速为14.54 m/h,运行结果表明:工艺抗冲击负荷能力较强、对各污染物的去除效果良好、系统运行稳定。在实际进水碳氮比较低的情况下仍能实现出水水质稳定达标。采用取消浓缩池、污泥脱水机房设为两层、部分构筑公用等措施,节约了用地面积,用地面积指标为0.52 m^(2)/(m^(3)·d)。

IFAS工艺处理市政污水的除污性能及节地潜力分析

采用生物膜／活性污泥组合工艺（IFAS）处理低C／N值市政污水，通过长达1年多的中试考察了温度、回流比和水力停留时间（HRT）对该工艺除碳和脱氮性能的影响，同时比较了IF—AS工艺和传统完全混合法（CSTR）的抗冲击负荷能力。结果显示：在填充比为35％、HRT为5．6h、DO为2mg／L、温度为20～25℃和回流比为75％的条件下，IFAS组合工艺除碳和脱氮效果较为理想，对COD、氨氮和TN的平均去除率分别为86．6％、92．9％和41．9％。与CSTR工艺相比，相同运行工况条件下WAS组合工艺不仅能提高33％的日处理能力，而且具备较强的同步硝化反硝化作用。由此可见，IFAS工艺具有较强的节地潜力，适用于传统污水处理厂的升级改造。