Abstract Population growth and climate change are exacerbating water scarcity. Graywater recycling could reduce water demand but it is not commonly practiced because of high treatment costs. Biochar, an emerging low-cost alternative sorbent with potential environmental benefits for graywater treatment, was compared to activated carbon (AC) for removing dissolved organic carbon (DOC) from graywater. The impact of pretreatments (coagulation, biodegradation) were also evaluated. Among five biochars tested, a wood-based biochar was the most effective for graywater treatment, but AC removed more DOC. Sorption resulted in a greater percent removal of ultraviolet (UV) absorbance than DOC or free chlorine demand. Graywater regulations could not be met by sorption alone but could be met with pretreatment before sorption. After biodegradation, irrigation and toilet flushing treatment targets could be achieved with AC doses less than 0.7 g/L, while a biochar dose of about 1 g/L was needed to achieve the irrigation treatment targets. For DOC removal, alum coagulation at a dose of 30 mg/L was a less effective pretreatment than biodegradation. Pretreatment and sorption to decrease turbidity and increase UV transmittance could be effective for the potential use of UV disinfection, thus creating an effective graywater non-potable reuse approach.

中文翻译：

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灰水处理的吸附、混凝和生物降解

摘要人口增长和气候变化正在加剧水资源短缺。灰水回收可以减少需水量，但由于处理成本较高，并未普遍采用。生物炭是一种新兴的低成本替代吸附剂，对灰水处理具有潜在的环境效益，在去除灰水中溶解的有机碳 (DOC) 方面与活性炭 (AC) 进行了比较。还评估了预处理（混凝、生物降解）的影响。在测试的五种生物炭中，木基生物炭对于灰水处理最有效，但活性炭去除了更多的 DOC。与 DOC 或游离氯需求相比，吸附导致紫外线 (UV) 吸光度的去除百分比更高。仅通过吸附无法满足灰水法规，但可以通过吸附前的预处理来满足。生物降解后，AC剂量小于0.7 g/L即可实现灌溉和冲厕处理目标，而生物炭剂量约为1 g/L才能实现灌溉处理目标。对于 DOC 去除，30 mg/L 剂量的明矾混凝预处理效果不如生物降解。预处理和吸附以降低浊度并增加紫外线透射率可能对紫外线消毒的潜在用途有效，从而创造一种有效的灰水非饮用水再利用方法。