【作者】 张冬梅；

【导师】 陈英旭；

【作者基本信息】 浙江大学 ， 环境工程， 2013， 博士

【摘要】 规模化养猪场排放的养殖废水属于我国农业面源重大污染源之一,其污染治理已被纳入环境保护的重要议程。但目前的养猪废水处理工艺均以氮磷生物转化与去除为目的,鲜见以资源化回收利用为核心的综合处理。本文以循环经济的发展理念为指导,通过研究猪场养殖废水经磷酸铵镁(MAP)结晶沉淀法处理后的氮磷回收效率以及沉淀过程对废水后续生化处理效果的影响,初步构建了一套猪场废水“MAP沉淀+厌氧CSTR+好氧SBR"联合处理工艺。研究表明,养殖废水通过磷酸铵镁(MAP)沉淀后可大幅度降低其原液中氮磷污染物含量,实现氮磷资源的高效回收；经MAP沉淀处理后的养殖废水再通过常规厌氧/好氧耦合工艺处理时,其厌氧段产甲烷效能可得到有效提升,并且最终经过好氧处理后COD、NH4+-N. PO43--P均可达到《畜禽养殖业污染物排放标准》(GBI8596-2001).研究成果为我国规模化养猪场养殖废水的资源回收和处理处置提出了一条新的技术模式。具体研究结论如下：1.养殖废水利用MAP沉淀预处理后可以高效回收其中氮磷资源,并显著降低和控制沉淀后尾水中NH4+-N、悬浮物和P043-P浓度,并通过全面分析得到pH值和P/Mg/N摩尔比对废水MAP沉淀处理效果的影响规律。将废水pH和P/Mg/N摩尔比调节为9.0和1/1.4/1.2时,MAP沉淀法可使养殖废水NH4+-N去除率达到87%,出水P043--P浓度降低至1.35mg/L;并且废水中COD、TOC、TC都得到一定程度地去除,去除率分别为22.3%、18.5%、23.1%；同时,废水中悬浮物的去除率均在80%以上。MAP沉淀产物的XRD检测结果表明,沉淀物中MgNH4PO4·6H2O的含量达到81.5%。2.猪场养殖废水经MAP沉淀处理后尾水C/N比和厌氧产沼效能都得到明显提高。MAP沉淀后尾水C/N比由原液的2.8提高到6.6。沉淀尾水与原废水的批式厌氧发酵对比实验表明,MAP沉淀后尾水TOC浓度降解速率明显加快,相同发酵时间内,可使废水COD、TOC和TC降解率分别提高11.7%、4%和8%,沼气和甲烷产量分别较原液提升0.307L/(g-VS)和0.295L-CH4/(g-VS)。CSTR连续流厌氧发酵实验结果表明,MAP沉淀后尾水与原液的COD容积负荷分别为2.2kg-COD/(m3-d)和1.5kg-COD/(m3-d),产气率分别为0.462m3/(kg-COD)和0.393m3/(kg-COD),气体中甲烷含量分别为67.9%和61.5%。3.采用SBR工艺分别处理CSTR厌氧后的MAP沉淀尾水和养殖废水原液,结果表明,在相同的操作模式下,MAP沉淀后尾水的COD. NH4+-N和P043--p的处理效果明显高于原液,平均去除率分别为82.8%、95.3%、94%和75.5%、74.5%、62%。且出水中NO2--N、NO3--N浓度低于原液,平均分别为48.6mg/L和8.6mg/L。4.养殖废水“MAP沉淀+厌氧CSTR+好氧SBR”工艺可以实现氮磷资源回收与污染物同时去除的目的。在稳态条件下运行“MAP沉淀+厌氧CSTR+好氧SBR”工艺结果表明,出水COD、NH4+-N和PO43--P浓度平均值分别为258mg/L,13mg/L和1.3mg/L,均达到《畜禽养殖业污染物排放标准》(GBI8596-2001),明显优于没有经过"MAP沉淀预处理”的“厌氧CSTR+好氧SBR”工艺的处理效果(其出水COD、NH4+-N和PO43--P浓度分别为424mg/L,256mg/L和25.67mg/L).对于C/N比相对较低的养殖废水处理,"MAP沉淀预处理”法实现了氮磷资源回收,达到显著改善废水的C/N比,更利于后续生化处理的目的。更多还原

【Abstract】 Swine wastewater is one of the major agricultural non-point source pollutants. In China, the treatment technology must meet the environmental protection standards. However, the existing processes of the treatments only aim to degrade or remove the NH4+-N and PO43--P without their recycling. This research utilized the new technique, MAP precipitation, as the pretreatment of the raw swine wastewater to precipitate the NH4+-N and PO43--P with MgNH4PO4·6H2O as struvite being a slow release fertilizer. In order to know the detailed influence on the subsequent process, various pollutants such as NH4+-N, PO43--P, COD, TOC and TC were monitored in the CSTR-SBR system with and without the MAP pretreatment. The results showed it is feasible to pretreat the swine wastewater with MAP technique, in which the NH4+-N and PO43--P were recycled. It improves the quality and quantity of biogas generation, and also the finally draining effluents easily meet the Chinese wastewater discharge standards. This paper offers a new idea in swine wastewater treatment. The main achievements in this research are as follows:1. The MAP technique can effectively lower down the NH4+-N and PO43--P concentrations in the supernatant of the swine wastewater after the precipitation; the removal efficiency of NH4+-N and the residual PO43--P were84.7%and1.35mg/L, and furtherly the COD, TOC and TC were also removed partly, the removal efficiency were22.3%,18.5%,23.1%, respectively, and the removal efficiency of SS all beyond80%seemed not to be influenced by the chemical dosage, the MAP contents MgNH4PO4·6H2O were maximum81.5%at pH9.0as tested by the XRD.2. The batch experiment in bottles of anaerobic fermentation was carried out after the MAP precipitation pretreatment. The results showed that NH4+-N concentration can be effectively controlled in the supernatants in the anaerobic process.the C/N ratio was enhanced from2.8to6.6. The amount of TOC remained130mg/L lesser than in the raw wastewater; while COD, TOC and TC degraded11.7%,4%and8%more than that in the raw wastewater, respectively. So, better performance of anaerobic treatment was gas yield rate and methane production at0.307L/(g-VS) against0.295L-CH4/(g-VS) higher than in the raw wastewater. The dynamics of anaerobic treatment with CSTR technology was studied in the supernatant and the raw swine wastewater. There was better performance in the supernatant and2or3days in advance in the supernatant at the same level degradation. The volume loading rate of the supernatant increased to2.2kg-COD/m3-d, but only1.5kg-COD/m3-d of the volume loading rate to the raw wastewater. At the same time, the gas rate between the supernatant and the raw were0.462and0.393m3/kg-COD, and the CH4contents were67.9and61.5%, respectively.3. Aerobic SBR technology was chosen for subsequent treatment of the effluents from the anaerobic digesters, the average removal efficiencies of COD, NH/-N and PO43--P of the effluents with and without pretreatment of MAP technique were82.8%,95.3%,94%and75.5%,74.5%,62%, respectively. The concentrations of NO2--N and NO3--N in the effluent of supernatants were48.6mg/L and8.6mg/L4. When the CSTR and SBR technology were combined together, the concentrations of NH4+-N, PO43--P and COD from the effluents of the supernatants pretreated with MAP technique were13.5,1.3and258mg/L, respectively, which met the Chinese discharge standard (GBI8596-2001).These values were256.1,25.67and424.4mg/L in the raw wastewater without MAP technique.更多还原