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为满足对畜禽养殖产品日益增长的需求,我国畜禽养殖业得到快速发展,因此,产生了大量畜禽粪污[1]。畜禽粪污经沼气工程后会将其生物质能转化为沼气,具有良好的经济效益[2-3]。但与此同时也会产生大量沼液。沼液中含有大量的病原菌、重金属,环境风险高,若随意排放或处理不当会污染生态环境,甚至危及人类健康[4-5]。
目前,规模化猪场粪污废水和沼液通常采用常规生化法处理,但一般效果较差,其中SS是最大的限制因素[6-7]。因此,沼液在进入生化处理前需要尽可能地去除SS。生物沥浸法是一种利用微生物调理,采用深度除渣机进行固液分离的技术。近年来,该技术主要用于环境污染领域的治理,如市政污泥的深度脱水[8-9],重金属污染土壤与河道底泥的生物修复[10-11],畜禽粪污中重金属的去除[12-13]等。该技术不仅可以有效回收污泥/粪污中的SS,脱除重金属,消除恶臭,绿色环保,而且经固液分离获得的泥饼(含水率低于60%)可用于资源化处理[14]。
对于猪场沼液采用生物沥浸法是否可行,相关研究报道较少。为此,本研究考察了不同浓度的营养剂对生物沥浸处理猪场沼液的影响,并重点考察了pH、比阻、泥饼重金属含量以及滤水水质等指标,以期为猪场沼液的处理提供借鉴和参考。
微生物营养剂浓度对生物沥浸法处理猪场沼液的影响
Effect of microbial nutrient concentration on bioleaching treatment of anaerobically digested piggery slurry
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摘要: 猪场沼液是规模化猪场沼气工程排出的具有高悬浮固体(SS)和高污染负荷的一类高浓度有机废水。采用生物沥浸法调理实现其深度固液分离,对该废水生化处理达标排放意义重大。通过摇瓶实验,研究了猪场沼液在不同浓度营养剂下的生物沥浸处理,并将获得的沥浸泥作为接种物回流,回流比为1∶1,共连续处理6批,测定pH、过滤比阻(SRF)、泥饼重金属含量及滤水水质等指标。结果表明:当营养剂浓度≥15 g·L−1,其处理效果较好且稳定;pH降至3.5以下,SRF降至5.0×1011 m·kg−1左右,脱水速率提高86.1%,泥饼重金属的浸出率高,其中Cu≥49.5%、Zn≥72.7%。沼液经生物沥浸处理后体积减少40%~50%,抽滤水的化学需氧量(COD)、氨氮(NH3)含量、总磷(TP)含量和SS分别从原稀释沼液的27 669.8、1 014.8、582.1 和27 857.1 mg·L−1降至423.8~499.3、671.4~704.0、0.7~1.1和0 mg·L−1,去除率最高可达98.5%、33.8%、99.9%和100%,大大降低了后续生化处理的难度。采用生物沥浸法处理猪场沼液具有良好的应用前景。Abstract: The anaerobically digested piggery slurry (ADPS) is a kind of organic wastewater with high suspended solids (SS) concentration and pollutant load discharged from large-scale pig farm biogas project. The complete solid-liquid separation through bioleaching conditioning followed by diaphragm pressure filter is of significance in ADPS biological purification. The bioleaching conditioning of ADPS with addition of different concentrations of microbial nutrient were performed through the flask-shaking experiment. Acidic already-bioleached ADPS was taken as an inoculum for next batch bioleaching experiment with the recycling ratio of 1∶1, and the corresponding recycling was conducted for successive six batches. The pH, specific resistance to filtration (SRF), heavy metal content in bioleached cake, and water quality indexes were measured. The results showed that when the concentration of microbial nutrient was ≥15 g·L−1, and good and stable bioleaching effect was achieved as following: the pH value and the SRF of bioleached ADPS could drop below 3.5 and about 5.0×1011 m·kg−1, respectively, and their dewaterability could increase by 86.1%. Under such a condition, the leaching percentages of Cu and Zn of the sludge-borne heavy metals were above 49.5% and 72.7%, respectively. After bioleaching treatment, the ADPS volume decreased by 40%~50%. The chemical oxygen demand (COD) content, ammonia nitrogen (NH3) content, total phosphorus (TP) content and SS of the filtered water could decrease to 423.8~499.3, 671.4~704, 0.7~1.1 and 0 mg·L−1 from the initial 27 669.8, 1 014.8, 582.1 and 27 857.1 mg·L−1, and the corresponding highest removal rates could reach 98.5%, 33.8%, 99.8% and 100%, respectively, which greatly reduced the difficulty in subsequent biochemical treatment. Therefore, bioleaching conditioning for ADPS has a good application prospect.
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表 1 猪场沼液的基本理化性质
Table 1. Basic physicochemical properties of anaerobically digested piggery slurry
pH 含固率/% SS/% COD/(mg·L−1) NH3/(mg·L−1) TP/(mg·L−1) SRF/(m·kg−1) Cu/(mg·kg−1) Zn/(mg·kg−1) 7.67 5.6 5.2 51 650.3 1 894.2 1 086.5 1×1013 967.2 1 809.4 表 2 生物沥浸处理后抽滤水COD、氨氮、总磷和悬浮固体含量
Table 2. COD, NH3, TP and SS content of filtered water after bioleaching
营养剂浓度/(g·L−1) COD/(mg·L−1) NH3/(mg·L−1) TP/(mg·L−1) SS/(mg·L−1) 10 423.8 671.4 1.1 0 15 453.4 691.8 0.7 0 20 499.3 704.0 1.0 0 表 3 生物沥浸处理后泥饼重金属Cu、Zn的浸出率
Table 3. Leaching percentages of Cu and Zn heavy metals in sludge cake after bioleaching
营养剂浓度/(g·L−1) Cu Zn 处理前/(mg·kg−1) 处理后/(mg·kg−1) 浸出率/% 处理前/(mg·kg−1) 处理后/(mg·kg−1) 浸出率/% 10 967.2 966.5 0.07 1 809.4 1 704.3 5.8 15 967.2 488.9 49.5 1 809.4 493.2 72.7 20 967.2 280.1 71.0 1 809.4 312.3 82.7 -
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