Application of subsurface wastewater infiltration system to on-site treatment of domestic sewage under high hydraulic loading rate

In order to enhance the hydraulic loading rate （HLR） of a subsurface wastewater infiltration system （SWIS） used in treating domestic sewage, the intermittent operation mode was employed in the SWIS. The results show that the intermittent operation mode contributes to the improvement of the HLR and the pollutant removal rate. When the wetting-drying ratio （RwD） was 1.0, the pollutant removal rate increased by （13.6 ± 0.3）% for NH3-N, （20.7 ± 1.1）% for TN, （18.6± 0.4）% for TP, （12.2 ± 0.5）% for BOD, （10.1 ± 0.3）% for COD, and （36.2 ± 1.2）% for SS, compared with pollutant removal rates under the continuous operation mode. The pollutant removal rate declined with the increase of the HLR. The effluent quality met The Reuse of Urban Recycling Water - Water Quality Standard for Scenic Environment Use （GB/T 18921-2002） even when the HLR was as high as 10 cm/d. Hydraulic conductivity, oxidation reduction potential （ORP）, the quantity of nitrifying bacteria, and the pollutant removal rate of NH3-N increased with the decrease of the RWD. For the pollutant removal rates of TP, BOD, and COD, there were no significant difference （p 〈 0.05） under different RwDS. The suggested RWD was 1.0. Relative contribution of the pretreatment and SWlS to the pollutant removal was examined, and more than 80% removal of NH3-N, TN, TP, COD, and BOD occurred in the SWIS.

Effect of Pretreatment on Physico-Chemical Parameters of Matrix and Pollutant Removals in Subsurface Wastewater Infiltration System

Two pilot subsurface wastewater infdtrafion systems （SWISs） were filled with the same mixed matrix and operated in the intermittent feeding mode with hydraulic loading of 0. 1 m3/ （m2 d） for 140 d. One of SWISs was fed with wastewater which was previously settled （ ST）, and the other with the same wastewater but in addition treated with a coagulation process （CT）. After 140 d of operation, in the upper layer of ST system the effective porosity decreased by 4.1% and the organic matter （OM） content increased by 246.4 %, whereas only decreased by 0.7 % and increased by 35. 7% of CT system, respectively. During the study, dogging didn＇t occur in CT system and occurred in ST system. Effluent chemical oxygen demand （COD）, total phosphorus （TP） and ammonia nitrogen （NH4＋ --N ） concentrations in CT system were less than those in ST system. In ST system, effluent COD, TP, NH4＋ --N concentrations increased and suspended solid （SS） concentration decreased after dogging. The results indicated that the use of a prior coagulation treatment was a good alternative for improving the effluent quality and avoiding an anticipated dogging.

Clogging Process Caused by Organic Particle Accumulation and Biofilm Growth in Subsurface Wastewater Infiltration System

Substrate clogging is the worst operational problem for subsurface wastewater infiltration system （ SWIS ）, nevertheless quantitative understanding of the clogging process is currently very limited. In this study, the developing process of clogging caused by organic particle accumulation and biofilm growth was investigated in two groups of lab-scale SWIS, which were fed with glucose （dissolved organic matter） and starch （particulate organic matter） influent and filled with the same substrate made of 50% brown soil and cinder at a weight of 50%. Results showed that in glucose-fed systems the growth of biofilm in the substrate pores certainly caused remarkable reduction of effective porosity, especially for the high concentration organic wastewater, whereas its influence on infiltration rate was negligible. In comparison with biofllm growth, organic particles accumulation could rapidly reduce infiltration rate and the clogging occurred in the upper layer in starch-fed systems and the most important contribution of biofilm growth to clogging was accelerating the occurrence of clogging.

Nitrogen Removal Improvement by Adding Peat in Deep Soil of Subsurface Wastewater Infi ltration System

In order to enhance the nitrogen removal, a subsurface wastewater infiltration system （SWIS） was improved by adding peat in deep soil as carbon source for denitrification process. The effects of addition of carbon source in the underpart of the SWIS on nitrogen removal at different influents （with the total nitrogen （TN） concentration 40 and 80 mg L^-1, respectively） were investigated by soil column simulating experiments. When the relatively light pollution influent with 40 mg L^-1 TN was used, the average concentrations of NO3-N and TN in effluents were （4.69±0.235）, （6.18±0.079） mg L^-1, respectively, decreased by 32 and 30.8% than the control; the NO3--N concentration of all effluents was below the maximum contaminant level of 10 mg L^-1; as high as 92.67% of the TN removal efficiency was achieved. When relatively heavy pollution influent with 80 mg LITN was used, the average concentrations of NO3--N and TN in effluents were （10.2±0.265）, （12.5±0.148） mg L^-1 respectively, decreased by 20 and 21.2% than the control; the NO3--N concentration of all effluents met the grade Ⅲ of the national quality standard for ground water of China （GB/T 14848-1993） with the values less than 20 mg L^-1; the TN removal efficiency of 94.1% was achieved. In summary, adding peat in the underpart of the SWIS significantly decreased TN and NO3- -N concentration in effluents and the nitrogen removal efficiency improved significantly.

Fate of nitrogen in subsurface infiltration system for treating secondary effluent

The concentration of total nitrogen(TN) is reported to vary between 20 and 35 mg/L in domestic wastewater. In raw wastewater, ammonia nitrogen eNHt4-NT is the main nitrogen form, accounting for 70%e82% of the TN concentration. Organic nitrogen, nitrite nitrogen eNOà2-NT,and nitrate nitrogen eNOà3-NT are present as well. For years, due to the lack of regulatory limits on nitrogen concentration in surface waters,nitrogen from secondary effluent has posed a significant threat to the health of aquatic ecosystems. Researchers have made substantial efforts to reduce the nitrogen concentration in secondary effluent. As a kind of advanced wastewater treatment technology, the subsurface infiltration(SI)system has been widely used, owing to its advantages, which include low operation cost, easy maintenance, and low energy consumption. This review discusses the fate of various forms of nitrogen in SI treatment, including organic nitrogen, NHt4-N, NOà2-N, and NOà3-N. Major biological processes involved in nitrogen removal and the main factors influencing its transformation are suggested. Finally, it is shown that ammonification followed by nitrification-denitrification plays a major role in nitrogen removal. Further research needs to focus on the emission characteristics of gaseous nitrogen(generated from the nitrification, denitrification, and completely autotrophic nitrogen-removal over nitrite(CANON) processes) with respect to their greenhouse effects.

地下渗滤处理村镇生活污水的中试

以红壤土作为填充土壤 ,在 2cm/d的水力负荷下 ,进行了地下渗滤系统处理村镇生活污水的现场中试 .结果表明 ,地下渗滤系统对COD、氨氮、总磷和总氮有着良好的去除效果 ,去除率分别达到 84 7%、70 0 %、98 0 %和 77 7% ,出水COD、氨氮、总磷和总氮的平均浓度分别为 1 1 7mg/L、4 0mg/L、0 0 4mg/L、4 7mg/L ,达到建设部颁发的生活杂用水水质标准 .对总氮去除机理的分析表明 ,由硝化 /反硝化实现生物脱氮是地下渗滤系统去除总氮的主要途径 .在本中试系统中 ,反硝化效果良好但硝化效果不够理想 ,改善土壤环境以促进硝化作用是提高总氮去除率的关键 .对土壤中氧化还原电位的测定结果表明 ,土壤内部的还原性质是阻碍硝化反应进行的主要原因 .

地下渗滤污水处理系统的氮磷去除机理

对地下渗滤系统处理生活污水的氮磷去除机理进行了研究.结果表明,在2cm/d的水力负荷下,系统对氨氮、COD、总磷的去除率可达到90%以上;出水中氨氮、COD、总磷分别低于0.2,30,0.025mg/L;系统对总氮亦有良好的去除效果,达63.5%.强化布水措施可以有效地提高系统对污染物质的去除率.地下渗滤系统中通过硝化、反硝化作用可以去除约50%的进水总氮,是地下渗滤系统去除氮的主要途径.改善条件以促进反硝化反应是提高地下渗滤系统总氮去除率的关键.土壤吸附与沉淀作用是地下渗滤系统去除磷的主要途径.

地下渗滤系统不同基质层对污染物的去除效果

以草甸棕壤为介质构建了污水地下渗滤模拟系统SWIS,监测有机污染物和氮、磷的浓度变化,研究不同深度基质中污染物的去除效果及削减规律.结果表明:进水负荷0.04m3.(m2.d)-1,散水深度55cm时,地下渗滤系统对有机物、氮、磷有较好的去除效果,去除率随时间延长趋向稳定,不同基质层对污染物的去除效果依次为Q(100)>Q(80)>Q(20)>Q(40)>Q(60);20～40cm基质层是有机物去除的主要范围,除污机制是物化吸附与生物降解;硝化作用主要发生在0～60cm的基质层,80cm以下区域反硝化作用为主导;基于Langmuir吸附模式的草甸棕壤磷最大吸附量为545.6mg.kg-1.

地下渗滤污水处理系统中基质的研究进展

地下渗滤污水处理系统是污水土地处理系统之一,可以同时实现污水就地处理与回用,受到了世界各国科学家的越来越广泛的重视。作为该系统的核心单元,基质成为研究热点之一。文中介绍了地下渗滤污水处理系统中基质的构成和作用,分析了影响系统性能的基质因素,提出了基质的选择原则,总结了目前的各种研究成果,并对今后的研究方向进行了展望,旨在为地下渗滤污水处理技术的理论研究和实践应用提供一定的借鉴意义。

滇池流域村镇生活污水地下渗滤系统设计

采用地下渗滤系统处理滇池流域的村镇生活污水,进行了工程的设计和建设。工程设计处理水量为30 m3/d,设计水力负荷为0.08 m3/(m2·d)。该工程对COD,总氮,总磷的去除率分别可以达到86.7％,85.5％和96.5％。工程的基建投资和运行费用不高,管理简单,兼具有美化景观的作用,并可产生一定的经济效益。

复合填料地下渗滤系统的强化脱氮研究

为有效提高地下渗滤系统的运行水力负荷并强化其脱氮效果,建立了由55%煤渣、25%土壤与20%草炭全混合装填的地下渗滤装置,运行水力负荷为10cm·d-1,每天进水4次,通过改变不同运行条件来促进TN的去除.研究结果表明该装置对COD,NH4+-N,TN的平均去除率,在正常出水水位条件下运行,分别为73.4%,98.2%和20.1%;在提高出水水位条件下运行,分别为75.4%,79.1%和26.9%;在添加碳源条件下运行,分别为88.9%,88.5%和55.7%.说明草炭的添加并不能明显提高TN的去除率,而出水水位的提高,可促进系统内厌氧环境的形成从而有利于TN的去除,但同时也会降低氨氮的去除效果;添加碳源可明显提高TN的去除效果,使系统出水TN质量浓度由正常出水水位条件下的22.8mg·L-1下降到14.2mg·L-1,且对COD和NH4+-N去除效果的影响不大.因此,影响该系统去除TN的关键因素是碳源的缺乏.

不同填料渗滤系统净化生活污水的效果比较

建立了2套不同填料的地下渗滤系统装置净化生活污水,1号装置由纯土壤装填,2号装置由土壤与砂分层装填,比较了2套装置对污染物的去除效果.2套装置运行了6个月,水力负荷为5 cm.d-1时每天进水4次,10 cm.d-1及20cm.d-1运行时每天进水8次.在水力负荷10 cm.d-1下运行,对化学需氧量(COD)、总磷、NH4+-N、总氮的去除率1号装置分别为80.7%,38.9%,48.7%,43.5%,2号装置分别为88.4%,87.2%,98.2%,24.9%;在水力负荷20cm.d-1下运行,1号装置发生堵塞现象无法运行,而2号装置对COD、总磷、NH4+-N、总氮的去除率分别为87.1%,56.1%,98.0%,28.9%,对COD及NH4+-N仍保持了良好的去除效果,并且保持了良好的水力渗透性能.研究结果表明,渗滤系统内部填料的改善提高了地下渗滤系统的运行水力负荷及其抗堵塞性能.

地下渗滤基质中微生物空间分布与污水净化效果

利用混菌法和稀释法,测定了稳定运行的地下渗滤系统不同深度的基质中微生物数量,并对其与污水净化效果进行了相关性分析.结果表明,不同空间位置的基质中微生物数量不同;不同月份基质中微生物数量变化不大;基质中微生物数量与COD、TN、NH4+-N去除率有显著的相关性,说明微生物的作用是其主要去除途径;但基质微生物数量与TP的去除率相关性不显著,说明TP去除与微生物基本无关.

地下渗滤系统在污水处理中的应用研究进展

地下渗滤系统是一种基于自然生态原理的污水净化技术 ,在我国有着良好的可行性和发展前景。本文总结介绍了地下渗滤系统的类型 ,概括分析了地下渗滤系统中的关键性问题———土壤的选择与配制、水力负荷的选取。

分流型地渗系统的污水强化脱氮研究

对传统型的地下渗滤系统进行了改进,建立了一套新型的地下渗滤试验装置。该装置成功启动65d后采用分层进水和连续操作的方式进行研究。结果表明,结构改进防止了堵塞,分层进水改善了系统抗冲击负荷的能力,提高了氮的脱除效率。在进水pH为7.8～8.0,HRT>10h的工况下,分流比为1:3时硝化和反硝化过程进行的最佳,此时总氮去除率达到60.34%,与未分流的去除率22.06%相比提高了近3倍。为分散污水的强化脱氮设计提供了新的思路。

改良地下渗滤系统处理生活污水的研究

通过添加自制的生物基质来改进污水地下渗滤系统(SWIS),并考察了改良污水地下渗滤系统(MSWIS)对生活污水的处理效果。结果表明,改良后的土壤具有较高的微生物活性,其理化条件也有明显的改善;与SWIS相比,MSWIS的启动周期缩短了20～30d;当进水COD为300mg/L、水力负荷为4～8cm/d时,MSWIS对COD的去除率比SWIS的提高了6.2%～8.8%;当水力负荷为4cm/d、进水COD为320～650mg/L时,MSWIS对COD的去除率比SWIS的提高了5.3%～8.9%。MSWIS具有较强的抗冲击负荷和抗污染负荷能力。

地下渗滤系统脱氮的研究进展

地下渗滤系统基于循环再生等生态学原理,在深度处理生活污水的同时,出水可二次回用,但脱氮问题一直没得到很好的解决.为了促进地下渗滤处理技术的快速发展,本文主要对地下渗滤系统的特征、除污原理以及地下渗滤系统脱氮作用的强化措施(如改善系统的氧化还原环境及二次布水等)进行了综述.建议采取适当的基质改良措施,科学改善系统内部的氧化还原环境,同时采用二次补水等技术强化系统脱氮.

污水地下渗滤系统强化脱氮试验研究

构建了3套以5%炉渣+95%草甸棕壤为基质的地下渗滤系统室内模拟试验装置,在水力负荷为0.1m3/(m2.d)条件下进行了生活污水处理试验.结果表明,当分流位置位于系统内110cm处,分流比为1:1时,可提高地下渗滤对总氮的去除效率,总氮的去除率由59.37%提高至68.41%,且对COD和总磷的去除效果没有影响.

污水地下渗滤系统脱氮效果及动力学过程

建立了模拟污水地下渗滤过程的中试系统,重点考察了水力负荷对系统脱氮效率的影响情况,建立了描述地下渗滤系统微生物脱氮过程的动力学模型。结果表明:地下渗滤系统脱氮效果好,抗水力负荷冲击能力强,处理最佳水力负荷0.125m.3m-.2d-1,出水中氮浓度低于《城市污水再生利用——景观环境用水水质》标准(GB/T 18921—2002)。地下渗滤系统硝化过程符合一级动力学模型NE=N0e-0.4812t,温度是影响硝化速率的主要因素,两者的关系是KT=0.2218×1.035(T-20);出水硝态氮浓度与水力停留时间之间呈负指数关系,可描述为C=16.3475e-0.2548t,碳源是引起反硝化速率变化的主要因子。在基质层垂直深度65 cm处二次补加生活污水,反硝化速率常数由0.0355提高到0.0488。强调地下渗滤系统的污水净化功能而忽视其生态服务功能,是系统运行中普遍存在的认识误区,过高的水力负荷不利于硝化-反硝化反应的顺利进行。地下渗滤系统运行应采取适宜的水力负荷方式,促进硝化-反硝化作用。

分流两段式土壤渗滤系统脱氮效果及机理研究

为解决传统土壤渗滤系统占地面积过大的问题,采用多级土壤渗滤系统和地下渗滤系统组合的新型两段式污水处理工艺,研究了在高水力负荷0.3m/d条件下分流比对其脱氮效果的影响,并通过实时定量PCR技术对不同层级的脱氮功能基因数量进行检测,进一步探究该系统中微生物脱氮机理.水质监测结果表明,分流措施可以显著提高两段式土壤渗滤系统在高负荷下的脱氮能力,当分流比为1:2时系统污染物去除能力最佳,对化学需氧量(COD)、总磷(TP)、氨氮(NH_4^+-N)、总氮(TN)的平均去除率分别达到91.16%、96.91%、72.11%和72.27%.脱氮功能基因丰度分析结果表明,多级土壤渗滤系统中的硝化及厌氧氨氧化和地下渗滤系统中的硝化反硝化的耦合作用是该工艺微生物脱氮的主要途径.