University of Minnesota, Department of Civil Engineering, 500 Pillsbury Ave SE, Minneapolis, MN 55455, USA.
Water Res. 2012 Jun 1;46(9):2937-46. doi: 10.1016/j.watres.2012.03.015. Epub 2012 Mar 22.
The presence of micropollutants can be a concern for land application of biosolids. Of particular interest are nonylphenol diethoxylate (NP(2)EO), nonylphenol monoethoxylate (NP(1)EO), and nonylphenol (NP), collectively referred to as NPE, which accumulate in anaerobically digested biosolids and are subject to regulation based on the environmental risks associated with them. Because biosolids are a valuable nutrient resource, it is essential that we understand how various treatment processes impact the fate of NPE in biosolids. Thermal hydrolysis (TH) coupled with mesophilic anaerobic digestion (MAD) is an advanced digestion process that destroys pathogens in biosolids and increases methane yields and volatile solids destruction. We investigated the impact of thermal hydrolysis pretreatment on the subsequent biodegradation of NPE in digested biosolids. Biosolids were treated with TH, anaerobic digestion, and aerobic digestion in laboratory-scale reactors, and NPE were analyzed in the influent and effluent of the digesters. NP(2)EO and NP(1)EO have been observed to degrade to the more estrogenic NP under anaerobic conditions; therefore, changes in the ratio of NP:NPE were of interest. The increase in NP:NPE following MAD was 56%; the average increase of this ratio in four sets of TH-MAD samples, however, was only 24.6 ± 3.1%. In addition, TH experiments performed in pure water verified that, during TH, the high temperature and pressure alone did not directly destroy NPE; TH experiments with NP added to sludge also showed that NP was not destroyed by the high temperature and pressure of TH when in a more complex sludge matrix. The post-aerobic digestion phases removed NPE, regardless of whether TH pretreatment occurred. This research indicates that changes in biosolids processing can have impacts beyond just gas production and solids destruction.
微污染物的存在可能是土地应用生物固体的一个关注点。特别值得关注的是壬基酚二乙氧基化物（NP(2)EO）、壬基酚单乙氧基化物（NP(1)EO）和壬基酚（NP），统称为 NPE，它们在厌氧消化的生物固体中积累，并根据与它们相关的环境风险进行监管。由于生物固体是一种有价值的营养资源，因此了解各种处理工艺如何影响 NPE 在生物固体中的命运至关重要。热水解（TH）与中温厌氧消化（MAD）相结合是一种先进的消化工艺，可破坏生物固体中的病原体，并提高甲烷产量和挥发性固体破坏率。我们研究了热水解预处理对消化生物固体中 NPE 随后生物降解的影响。在实验室规模的反应器中，用 TH、厌氧消化和有氧消化处理生物固体，并分析消化器的进水和出水的 NPE。在厌氧条件下，NP(2)EO 和 NP(1)EO 已被观察到降解为更具雌激素的 NP；因此，NP:NPE 比值的变化很有意思。MAD 后 NP:NPE 的增加了 56%；然而，在四组 TH-MAD 样品中，该比值的平均增加仅为 24.6±3.1%。此外，在纯水中进行的 TH 实验验证了，在 TH 过程中，高温和高压本身不会直接破坏 NPE；在含有 NP 的污泥中进行的 TH 实验也表明，当 NP 处于更复杂的污泥基质中时，TH 的高温和高压不会破坏 NP。无论是否进行 TH 预处理，后有氧消化阶段都能去除 NPE。这项研究表明，生物固体处理的变化可能会对气体产生和固体破坏产生影响。
