臭氧降解垃圾渗滤液膜滤浓缩液的影响因素及光谱特性

研究臭氧氧化对垃圾渗滤液浓缩液中有机物去除机制,为臭氧氧化技术处理腐殖化程度较高的垃圾渗滤液膜滤浓缩液的应用提供基础数据与技术支撑。垃圾渗滤液处理工艺为A2/O+MBR+NF(RO),渗滤液浓缩液表观呈棕黄色,无恶臭;pH值7.98,CODCr5 492 mg/L,BOD5/CODCr为0.01,荧光指数f(450/500)1.45,生物源指数BIX为0.81,腐殖化指数HIX 14.95。研究反应时间、臭氧投量、进水CODCr浓度、初始pH值、反应温度等因素对垃圾渗滤液浓缩液中有机物去除机制及其光谱特性。结果表明:在反应时间为90 min、臭氧投量为1.67 g/h和室温为27℃的条件下,CODCr和CN(色度)去除率分别为37.6%、58.0%,BOD5/CODCr从0.01提升到0.39;增加反应时间、臭氧投量和反应温度可促进渗滤液浓缩液的降解,而降低体系CODCr浓度和pH值则不利于腐殖质类物质的削减;紫外-可见光谱分析表明臭氧处理过程可极大程度改变废水的腐殖化程度,芳香物质去除较为明显;三维荧光光谱分析表明臭氧可有效降解浓缩液中的可见光区类富里酸,且经臭氧处理后的渗滤液浓缩液分子结构趋于简单。     

膜集成工艺处理海水工厂化养殖废水技术研究

采用砂滤、精密过滤、超滤、紫外杀菌和膜法充氧工艺,建立一套0.5 m3/h膜集成试验装置,用于处理海水工厂化养殖废水。考察超滤膜性能、试验工艺对废水中主要污染物的去除效果。结果表明:超滤膜截留率增大,COD去除率提高,产水量下降;选用截留率(牛血清白蛋白)为97.0%超滤膜,不投加混凝剂,装置对污水中COD、TN、TP和细菌的去除率依次为66.1%、69.7%、11.9%和100%,产水溶解氧达到39.54 mg/L,产水浊度为0.40 NTU,投加聚合氯化铝未能有效提高产水水质。除总磷外,膜法处理后海水的各项水质指标满足GB 3097—1997《海水水质标准》养殖用水要求。     

絮凝-CO2曝气-催化氧化处理制革废水研究

使用新型高效的絮凝剂MF，对制革废水进行絮凝吸附、CO2曝气、催化氧化回用处理试验，确定了絮凝剂MF的最佳使用条件、催化氧化时间和氧化剂用量。结果表明，制革废水经工艺处理后，对废水中主要污染物CODcr、S^2-、Cr^3 、SS、色度去除率分别达到78．9％、97.5％、95．5％、91．4％、96．5％。处理后的废水基本达到鞣铬工艺用水要求和国家《污水综合排放标准》(GB8978-1996)限定的二级标准。     

一体式MBR对水产养殖废水处理操作参数优化的研究

为考察一体式膜生物反应器(一体式MBR)对养殖废水主要污染物去除效果的影响,研究一体式MBR处理水产养殖废水的最优操作参数,将操作参数HRT、曝气量、MLSS进行组合设计,考察其对COD、NH3-N、NO-2-N、NO-3-N、TN、TP去除率的影响。结果显示,各操作参数对出水水质指标的影响程度大小依次为MLSSHRT曝气量。根据综合平衡法,反应器最佳的操作参数组合为:HRT 3.25 h、曝气量375 L/h、MLSS2.2 g/L。     

菱角对农村富营养化水体营养盐吸收的初步研究

为探究浮叶植物对农村富营养化废水中营养盐的去除效果,选定华龙村4个典型水塘,以人工种植菱角(Trapa bispinosa)为试验对象,研究菱角对富营养化水体中总氮(TN)、硝态氮(NO_3~--N)、氨态氮(NH_4~+-N)、总磷(TP)及化学需氧量(CODCr)的净化能力。结果表明,经过75 d的试验研究,试验区水塘的TN、NH_4~+-N和NO_3~--N的浓度分别从55 mg/L、25 mg/L和3 mg/L降至13 mg/L、4.3 mg/L和2.1 mg/L,去除效率分别为62.3%、74.5%和23.5%;TP及CODCr的浓度从3.3 mg/L和120 mg/L分别降至1.45 mg/L和52.5 mg/L,去除效率为56.9%和56.3%;对照区水塘各营养元素去除率较低。菱角对农村废水中的N、P有一定的吸收作用,对重度富营养化水体,水生植物优先吸收NH_4~+-N,对TN的去除影响较大;NO_3~--N的去除主要依靠微生物的反硝化作用;TP的吸收需要更长的时间。菱角对重度富营养化农村废水营养盐的去除具有重要意义,且可以取得一定的经济效益。本研究为应用水生植物处理农村生活污水中的营养盐提供科学依据。     

高锰酸钾氧化池塘藻毒素的研究

研究了高锰酸钾KMnO4对池塘微囊藻毒素(MC-LR)的去除效果,探讨反应影响因素(高锰酸钾质量浓度、温度、pH值、反应时间)对去除率的影响.结果表明,高锰酸钾能有效地去除水中的微囊藻毒素.高锰酸钾对MC-LR的去除率与高锰酸钾投加的质量浓度、温度、反应时间成正相关,其中高锰酸钾质量浓度对去除率的影响最大;其次为温度和pH,当温度为35℃时,去除率可达96.65%,当pH为3时,去除率也达到了95.1%;反应时间对去除率的影响不太显著.正交试验的结果也进一步证明了这一点.     

臭氧对循环水养殖水体水质的净化效果及机理研究

为了探讨臭氧对循环水系统养殖水体水质的净化效果及作用机理,开展3种不同臭氧投加量对水体中有机污染物和氨氮、亚硝酸盐等作用影响的试验,并在此基础上对净化机理进行分析。结果显示:臭氧优先与有机污染物发生反应,其次为亚硝酸盐,然后才是氧化氨氮;臭氧对有机物的去除是选择性的,优先降低UV_(254)和水色,对于COD和DOC处理效果不明显,但能显著提高养殖水的可生化性; 15 mg/L的臭氧投加量可取得较经济适宜的净化效果,对于UV_(254)、亚硝酸盐、水色、COD分别可降低73. 86%、92. 35%、37. 52%和16. 43%,并将DOC/UV_(254)比值升高到448. 86 (cm·mg)/L,显著提高养殖水的可生化性。研究表明:臭氧氧化技术在养殖水体净化处理中发挥了良好作用,针对不同情况选择适宜的臭氧投加量对于提高净化处理效率有重要意义。     

高锰酸钾氧化池塘藻毒素的研究

研究了高锰酸钾KMnO4 对池塘微囊藻毒素(MC - LR) 的去除效果, 探讨反应影响因素(高锰酸钾质量浓度、温度、pH 值、反应时间)对去除率的影响。结果表明, 高锰酸钾能有效地去除水中的微囊藻毒素。高锰酸钾对MC- LR的去除率与高锰酸钾投加的质量浓度、温度、反应时间成正相关, 其中高锰酸钾质量浓度对去除率的影响最大; 其次为温度和pH, 当温度为35e 时, 去除率可达96. 65%, 当pH 为3时, 去除率也达到了95. 1%; 反应时间对去除率的影响不太显著。正交试验的结果也进一步证明了这一点。     

蟹壳脱除废水中重金属离子的研究

采用颗粒状蟹壳对废水中镉和铅进行吸附去除实验,研究蟹壳不同预处理方法、吸附剂投加量、初始金属浓度、溶液初始pH值、动力学因素、不同温度条件下对蟹壳生物吸附剂吸附Cd^2＋和Pb^2＋的影响。结果表明,在40c时,Cd^2＋溶液初始浓度200mg／L,蟹壳生物吸附剂量4g／L,溶液初始pH为6时对Cd^2＋的吸附量最大,去除率达到89．25％;Pb^2＋溶液初始浓度1000mg／L,蟹壳生物吸附剂量2．4g／L,溶液初始pH为5时对Pb^2＋的吸附量最大,去除率达到98．7％。蟹壳对Pb^2＋和Cd^2＋的吸附符合Langmuir吸附等温模型。获得的动力学数据表明,吸附速度快,Cd^2＋大部分的吸附进程在2小时内完成,Ph^2＋大部分的吸附进程在3／b时内完成,随后是缓慢地实现平衡,较高的相关系数符合HoYS二级吸附动力学模型。     

UV/Fenton法处理低浓度含镍络合废水研究

为了有效去除低浓度含镍络合废水中的镍离子(Ni~(2+)),探究影响Ni~(2+)去除效果的因素和方法,通过改变低浓度溶液中沉淀pH值、H_2O_2与Fe~(2+)摩尔比、H_2O_2投加量、初始pH值和反应时间,基于UV/Fenton法,研究了以上各因素对Ni~(2+)去除效果的影响及机理;同时比较UV/Fenton法与Fenton法对Ni~(2+)的去除效果,自配含有典型络合剂的镀镍模拟废水,酒石酸∶柠檬酸∶乙二胺四乙酸∶镍(摩尔比)为1.5∶2∶1.5∶1,Ni~(2+)含量5 mg/L,pH 4.0;光催化实验在光化学反应仪中进行,反应系统由循环水冷却,维持温度在(32±2)℃,光强度为12.7 mW/cm~2。50 mL的石英管中依次加入模拟络合镍废水和一定量的Fenton试剂,100 W中压汞灯光照下进行连续磁力搅拌;光照一定时间后,NaOH调节pH至11.0,离心后取上清液测定镍含量,测定方法采用火焰原子吸收分光光度计。结果显示,UV/Fenton法去除Ni~(2+)的最佳反应条件为初始pH值2.6左右,H_2O_2∶Fe~(2+)(摩尔比)为3∶1,H_2O_2投加量为3 mmol/L,反应时间为1 h,沉淀pH值为11.0,Ni~(2+)去除率可达98%以上。研究表明,增大沉淀pH值、合理控制H_2O_2浓度、增加反应时间,可提高低浓度镍络合物中Ni~(2+)的去除效果;相较于单一Fenton法,采用UV/Fenton法可更好的去除低浓度镍络合物中的Ni~(2+)。     

Coagulation of phosphorous and organic matter from marine,land-based recirculating aquaculture system effluents

Saline effluents from marine land-based aquaculture production can neither be disposed in common municipal wastewater treatment plants, nor disposed as landfill. Furthermore, stricter environmental regulations require the reduction of phosphorous and organic matter levels from marine environment discharges to minimize eutrophication. Chemical coagulation with FeCl₃ and AlSO₄ is commonly used for removing phosphorous and suspended solids in wastewater treatment. The capacity of these coagulants for creating particle aggregations depends on the characteristics and chemistry of the treated wastewater, such as the ionic strength or mixing conditions. Marine water has a higher ionic strength than fresh or brackish water, which may be beneficial when using chemical coagulants to treat the effluents from farms operated at high salinities. The following study compared the application of FeCl₃ and AlSO₄, to treat the two effluents discharged from a marine land-based recirculating aquaculture system (RAS) producing salmon (Salmo salar). The aim of the study was to determine; 1) in what effluent (sludge flow vs. exchange water overflow) at the end-of-pipe treatment the coagulant application is more efficient for the removal of PO₄³⁻-P, total suspended solids (TSS), total phosphorous (TP) and total chemical oxygen demand (TCOD); and 2) the optimal coagulant dose to apply and its associated chemical sludge production. The results show that more than 89 % removal of TCOD, TSS and TP is achieved when treating the sludge flow, arguably because the sludge flow contained the largest fraction of the target masses (P and organic matter) discharged from the system. Up to 80 % of TSS removal was achieved by simple sedimentation, and with the highest coagulant dose tested, up to 95 % of TSS could be removed from the effluent. To remove 90 % of PO₄³⁻-P, FeCl₃ and AlSO₄ need to be dosed at a molar ratio of 2.6:1 Fe:PO₄³⁻-P and 5.7:1 Al: PO₄³⁻-P, respectively. Dosing above 90 % removal efficiency did not significantly affect removal of PO₄³-P and TSS, but substantially increased the volume of chemical sludge produced. Finally, FeCl₃ is proposed as a better overall alternative for P removal at the end-of-pipe treatment in marine land-based RAS.     

Evaluation of geotextile filtration applying coagulant and flocculant amendments for aquaculture biosolids dewatering and phosphorus removal

Wastes contained in the microscreen backwash discharged from intensive recirculating aquaculture systems were removed and dewatered in simple geotextile bag filters. Three chemical coagulation aids (aluminum sulfate (alum), ferric chloride, and calcium hydroxide (hydrated lime)), were tested in combination with a long-chain polymer flocculation aid (HyChem CE 1950 at 25 mg/L) to determine the most cost effective and efficient treatment combination. Three different coagulants were tested to determine if coagulant choice impacts nutrient and carbonaceous biochemical oxygen demand (cBOD₅) leaching into the filtrate and the final composition of the bag-captured biosolids at the end of each period. If nutrient leaching into the bag filtrate could be minimized through coagulant selection, then geotextile bags could provide a convenient and effective method to dewater waste biosolids and provide them in a form that fish farmers could readily transport, store, or send for disposal.Results from replicate geotextile bag filter tests indicate that when alum, ferric chloride, and hydrated lime (plus a polymer) were amended to a backwash flow, both suspended solids capture and solids thickening were improved; i.e., total suspended solids removal rates of 95.8, 95.1, and 96.0%, respectively, were achieved along with final dewatered filter cake percent solids concentrations of 22.1, 19.3, and 20.9%, respectively. Alum, ferric chloride, and hydrated lime (plus a polymer) amended geotextile bags were not as effective in chemical oxygen demand (COD) and cBOD₅ removal, resulting in removal rates of 69.6, 67.2, and 35.3%, respectively, and 56.6, 9.3, and ?47.4%, respectively. Further, the use of lime as a coagulant resulted in filtrate COD and cBOD₅ concentrations that exceeded inlet concentrations. Total nitrogen removal applying alum, ferric chloride, and lime were also less than effective, resulting in removal rates of 39.1, 46.7, and ?8.9%, respectively. Filtrate total nitrogen concentrations were primarily in the inorganic form (total ammonia nitrogen) suggesting mineralization of ammonia as solids were stored within geotextile bags under anaerobic conditions. Alum, ferric chloride, and lime amended bags were moderately efficient at total phosphorus removal, resulting in removal rates of 67.6, 47.0, and 77.3%, respectively. Alum was identified as the most cost effective chemical for coagulation, but hydrated lime was the most effective at dissolved phosphorus precipitation and removal.     

CO2体积浓度对酒精废水培养微藻及其净化效果的影响

从4种常见微藻中筛选出能够充分利用木薯酒精废水及CO2废气生长的种类,并探究CO2体积浓度对其生长及净化废水中总氮(TN)、总磷(TP)、化学需氧量(CODCr)能力的影响。通过微藻在废水中生长的干重变化及叶绿素a(Chl-a)含量判断其生长情况,筛选出最适合的微藻。通过单因子试验,研究不同CO2体积浓度对筛选微藻的干重及叶绿素a(Chl-a)含量,以及CO2固定速率的影响,来寻找最适合生长的质量浓度。通过测定废水中TN、TP、CODCr的变化来评估净化作用。筛选试验结果表明,钝顶螺旋藻(Spirulina platensis)能适应酒精废水和CO2废气中的生长环境,在未经稀释的酒精废水中,其干重和Chl-a均显著高于波吉卵囊藻、普通小球藻和四尾栅藻(P<0.05)。单因子试验结果显示,当通入体积浓度2.5%的CO2,在酒精废水中培养的钝顶螺旋藻的干质量为(1.62±0.05)g/L、Chl-a为(12.1±0.7)mg/L,均高于其他试验组(P<0.05)。同时其对酒精废水中TN、TP、CODCr的去除率显著最高,分别为(50.5±2.1)%、(73.2±2.0)%及(24.9±0.6)%。钝顶螺旋藻能够适应酒精废水的生长环境,能吸收利用CO2废气,并有不错的净化效果。最适合其生长的CO2体积浓度是2.5%。     

不同流向对曝气生物滤池处理对对虾养殖污水效果的影响

采用上流式和下流式曝气生物滤池处理凡纳滨对虾(Litopenaeus vannamei)养殖污水,连续进行30 d,分析出水水质,并观察系统运行情况和装置污染状况。研究了养殖污水中化学需氧量、氨氮、硝酸盐氮、亚硝酸盐氮、无机氮及活性磷酸盐6项指标的去除效果。实验结果表明:从养殖污水主要污染物指标的去除效果和稳定性上看,上流式优于下流式曝气生物滤池。在系统进水化学需氧量质量浓度为7.62～8.20 mg/L、氨氮质量浓度为0.62～0.65 mg/L、硝酸盐氮质量浓度为0.54～0.59 mg/L、亚硝酸盐氮质量浓度为0.23～0.27 mg/L、无机氮质量浓度为1.40～1.47 mg/L、活性磷酸盐质量浓度为0.24～0.29 mg/L,水温为25℃～30℃时,上流式曝气生物滤池对养殖污水中6项指标的去除率分别为:45.2%、88.9%、58.5%、78.8%、75.3%和25.1%。可见,对氨氮的去除效果最佳,亚硝酸盐氮和无机氮次之,化学需氧量和硝酸盐氮的去除效果较差,活性磷酸盐去除率最低。     

生化尾水胁迫下湿地植物生理特性变化

检测植物处理污水厂生化尾水的效果和分析植物生理生长特性,为西北干旱半干旱地区人工湿地污水处理系统合理配置土著湿地植物提供理论依据。在复合垂直流-水平流人工湿地中种植芦苇和香蒲,生活污水处理装置的二级生化出水胁迫,植物移栽成活后和收割之前分别检测植物的生理、生长指标和光合参数。结果表明,COD_(Cr)、NH~+_4-N、TN、TP的去除率,种植植物期间分别为79.32%、85.69%、82.17%、91.76%,植物收割后分别为71.34%、58.45%、60.49%、89.86%;芦苇最高株高达到380 cm,香蒲最高株高达到320 cm;地上部分生物量香蒲最高达到4.15kg,芦苇最高达到7.55 kg;香蒲的净光合速率(P_n)分别增加了6.35%、3.99%、22.39%,芦苇的净光合速率(P_n)则分别增加了42.20%、5.26%、8.96%。2种湿地植物在污水胁迫下表现出一定的防御能力,但是抗污能力存在一定的差异。     

Assessment of the use of precipitating agents and ceramic membranes for treatment of effluents with high concentrations of nitrogen and phosphorus from recirculating aquaculture systems

Following the culturing of post‐juvenile African catfish, wastewaters were purified using single and integrated processes. Iron coagulant (IC), aluminium coagulant (AC), lanthanum modified bentonite (LMB) and ceramic membranes (NF – nanofiltration) were each tested in single processes, while the combination of IC + NF and AC + NF were used in the integrated process tests. Among the single processes, membrane filtration was the most effective in purifying the aquaculture effluent. The total suspended solids (TSS) were removed entirely and there was a near‐complete removal of turbidity (99.2%), as well as effective removal of Al and Fe (80.8% and 67.4% respectively). Precipitating agents overall removed TSS most faithfully, from 37.5% removal with AC, through 50.2% with IC, to 62.3% with LMB. Using integrated processes, the highest removal efficacy was recorded for TSS (100%) and turbidity (99.7% – IC + NF; 99.9% – AC + NF). Additionally, integrated processes attained a 96.8%–98.4% removal of NO₂^‐‐N. This study confirms the possibility of using IC, AC and LMB in chemical purification of effluents from recirculating aquaculture systems (RAS). However, due to their low removal efficacy for nitrogen and phosphorus, it is preferable to use NF or integrated processes – membrane filtration combined with chemical precipitation, methods which proved to be most effective for water purification in RAS.     

低功率密度超声波强化絮凝沉降除藻技术研究

超声波强化絮凝沉降除藻技术能够提高絮凝沉降除藻效率,但以往研究采用的较高超声波功率限制了这一组合技术的应用。通过探究低功率密度超声波(0.5～1.0 W/L)对絮凝沉降技术去除微囊藻的增效作用,比较了增重剂种类及用量、超声波预处理的时间和距离、超声波预处理与絮凝沉降的间隔时长、日光照射时长等因素对除藻率的影响,并通过水池试验验证了低功率密度超声波的增效作用。结果显示:(1)超声波的处理距离对除藻率无显著影响,但增加超声波预处理时长则明显有利于提高除藻率,处理30 s时的除藻率显著高于仅处理10 s时的除藻率;(2)除藻率的日均变幅较大,当日光光照时长为3～9 h时,试验组的除藻率平均比对照组高17%,日光照射时长为0 h和12 h时,试验组与对照组的除藻率则无显著差异;(3)随着超声波预处理与絮凝沉降间隔时长的增加,除藻率会明显下降,仅当间隔时长不超过30 min时,试验组的除藻率才显著高于对照组;(4)水池原位试验中,试验组的除藻率高达70.47%,显著高于对照组的58.12%。研究表明,低功率密度超声波预处理能明显增加絮凝沉降除藻率,且应在日光开始减弱的下午作业。     

高盐环境下Cr(Ⅵ)/亚硫酸盐体系氧化降解效能研究

鉴于亚硫酸盐处理含铬Cr(Ⅵ)废水时会产生氧化性极强的硫酸根自由基和羟基自由基,使得亚硫酸盐的消耗量增加,为提高亚硫酸盐的利用率并将产生的活性自由基加以利用,选取了常见的偶氮染料酸性橙7(AO7)作为目标有机污染物用以捕获产生的活性自由基,以达到含Cr(Ⅵ)废水和有机污染废水协同处理的目的。通过紫外可见吸收光谱法和显色法测定AO7、Cr(Ⅵ)和亚硫酸盐等各反应物的浓度变化,采用自由基捕获方法鉴定反应中的活性氧化物种。结果表明,Cr(Ⅵ)/亚硫酸盐体系能够在降解AO7的同时,将Cr(Ⅵ)转化为Cr(Ⅲ), S(Ⅳ)氧化为硫酸根离子。在[Na_2SO_3]_0=0.5 mM、[Cr⁶⁺]_0=0.1 mM、pH=3.0条件下,Cr(Ⅵ)/亚硫酸盐体系对AO7的降解效果最好,反应60 min后,AO7降解率和Cr(Ⅵ)的还原率分别为86.1%和82.0%,且氯离子Cl^-的加入几乎无影响。在反应体系中加入0.1 mM乙醇或叔丁醇后,AO7的降解受到不同程度影响,在Cl^-=0/300 mM条件下,AO7的降解率分别变为56.6%/71.7%和80.7%/81.5%,证明该体系中的主要氧化物为SO■和·OH,且起主要作用的是SO■。AO7降解实验、可吸附卤代物(AOX)和气相色谱-质谱联用(GC-MS)结果表明,Cr(Ⅵ)/亚硫酸盐体系在高盐环境下能保持较高的降解效率,且不会增加氯代二次产物的生成,这种新型的氧化降解体系有望在高盐工业废水处理中得到应用。     

高盐环境下Cr(VI)/亚硫酸盐体系氧化降解效能研究

鉴于亚硫酸盐处理含Cr(VI)废水时会产生氧化性极强的硫酸根自由基和羟基自由基，使得亚硫酸盐的消耗量增加，为提高亚硫酸盐的利用率并将产生的活性自由基加以利用，选取了常见的偶氮染料酸性橙7(AO7)作为目标有机污染物用以捕获产生的活性自由基，以达到含Cr(VI)废水和有机污染废水协同处理的目的。通过紫外可见吸收光谱法和显色法测定AO7、Cr(VI)和亚硫酸盐等各反应物的浓度变化，采用自由基捕获方法鉴定反应中的活性氧化物种。结果表明，Cr(VI)/亚硫酸盐体系能够在降解AO7的同时，将Cr(VI)转化为Cr(III), S(IV)氧化为硫酸根离子。在[Na2SO3]0=0.5 mM、[Cr6+]0=0.1 mM、pH=3.0条件下，Cr(VI)/亚硫酸盐体系对AO7的降解效果最好，反应60 min后，AO7降解率和Cr(VI)的还原率分别为86.1%和82.0%，且氯离子的加入几乎无影响。在反应体系中加入0.1 mM乙醇或叔丁醇后，AO7的降解受到不同程度影响，在Cl?= 0/300 mM条件下，AO7的降解率分别变为56.6%/71.7%和80.7%/81.5%，证明该体系中的主要氧化物为SO4?? 和?OH，且起主要作用的是SO4??。AO7降解实验、可吸附卤代物(AOX)和气相色谱-质谱联用(GC-MS)结果表明，Cr(VI)/亚硫酸盐体系在高盐环境下能保持较高的降解效率，且不会增加氯代二次产物的生成，这种新型的氧化降解体系有望在高盐工业废水处理中得到应用。     

Growth and potential purification ability of Nitzschia sp. benthic diatoms in sea cucumber aquaculture wastewater

The growth patterns and water treatment capacity of Nitzschia sp. benthic diatoms in different concentrations of sea cucumber aquaculture wastewater (0%, 10%, 30%, 50%, 80% and 100%) and f/2 medium were studied. Nitzschia sp. grew in different concentrations of aquaculture wastewater and showed remarkable differences in their rate of growth among the treatment groups. Nitzschia sp. grew most quickly (0.83 ind/day) and showed the greatest total chlorophyll‐a content in 30% wastewater. The total chlorophyll‐a content and growth rate of Nitzschia sp. were strongly correlated (R² > 0.98). The total lipid (TL), total protein, exopolysaccharide (EPS) and intracellular polysaccharide (IPS) contents of the diatoms were highest in 100% wastewater and showed significant differences among the experimental groups (p < 0.05). Total nitrogen (TN), ammonium‐nitrogen (NH₄‐N) (AN), nitrate nitrogen (NO₃‐N) (NN), nitrite nitrogen (NO₂‐N) (NIN) and total phosphate (TP) contents were significantly reduced after cultivation. TN uptake peaked at 54.58% in 30% wastewater. AN uptake exceeded 95% in 30% wastewater and 100% wastewater. NN uptake peaked at 56.42% in 80% wastewater, whereas TP uptake ranged from 16.80% to 27.69%. These results suggest that Nitzschia sp. biomass can be enhanced via cultivation in low‐concentration (30%) wastewater, after which their cultivation may be continued in high‐concentration (100%) wastewater, increasing their nutritional value and aiding in the removal of surplus nitrogen and phosphorus in sea cucumber aquaculture wastewater. Application of Nitzschia sp. using the recirculating wastewater‐treatment methods described has the potential to reduce environmental harm caused by sea cucumber cultivation and thus achieve sustainable aquaculture.