The broader reuse of sewage sludge as a soil fertilizer or conditioner is impeded by the presence of toxic metals. Bioleaching, a process that leverages microbial metabolisms and metabolites for metal extraction, is viewed as an economically and environmentally feasible approach for metal removal. This study presents an innovative bioleaching process based on microbial oxidation of ammonia released from sludge hydrolysis, mediated by a novel acid tolerant ammonia-oxidizing bacteria (AOB), Nitrosoglobus. Over a span of 1024 days, a laboratory-scale bioleaching reactor processing anaerobically digested (AD) sludge achieved an pH of 2.5 ± 0.3. This acidic environment facilitated efficient leaching of toxic metals from AD sludge, upgrading its quality from Grade C to Grade A (qualified for unrestricted use), according to both stabilization and contaminants criteria. The improved quality of AD sludge could potentially reduce sludge disposal expenses and enable a broader reuse of biosolids. Furthermore, this study revealed a pH-dependent total ammonia affinity of Nitrosoglobus, with a higher affinity constant at pH 3.5 (67.3 ± 20.7 mg N/L) compared to pH 4.5–7.5 (7.6 – 9.6 mg N/L). This finding indicates that by optimizing ammonium concentrations, the efficiency of this novel ammonium-based bioleaching process could be significantly increased.

中文翻译：

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在连续生物反应器中对污水污泥中的有毒金属进行铵基生物浸出

有毒金属的存在阻碍了污水污泥作为土壤肥料或改良剂的更广泛的再利用。生物浸出是一种利用微生物代谢和代谢物提取金属的过程，被认为是一种经济和环境可行的金属去除方法。本研究提出了一种创新的生物浸出工艺，该工艺基于污泥水解释放的氨的微生物氧化，由新型耐酸氨氧化细菌 (AOB) Nitrosoglobus 介导。在 1024 天的时间里，处理厌氧消化 (AD) 污泥的实验室规模生物浸出反应器的 pH 值达到了 2.5 ± 0.3。这种酸性环境促进了 AD 污泥中有毒金属的有效浸出，根据稳定性和污染物标准，将其质量从 C 级提升到 A 级（符合不受限制使用的条件）。 AD 污泥质量的提高可能会减少污泥处置费用，并实现生物固体的更广泛的再利用。此外，这项研究揭示了 Nitrosoglobus 的 pH 依赖性总氨亲和力，与 pH 4.5–7.5 (7.6 – 9.6 mg N/L) 相比，pH 3.5 (67.3 ± 20.7 mg N/L) 下的亲和常数更高。这一发现表明，通过优化铵浓度，可以显着提高这种新型铵基生物浸出工艺的效率。