Treatment optimization of greywater from the combined use of chemical coagulants

ABSTRACT With the growing demand and shortage of water, efforts are needed to enable alternative sources of supply. Thus, this work was focused on optimizing the treatment of greywater by associating the chemical coagulants aluminum sulfate and ferric chloride, to enable their reuse. Therefore, the research was divided into three stages: characterization greywater from basin and shower of a single-family residence; assessing the combined use of aluminum sulfate and ferric chloride, prepared in 5% solution for the treatment of greywater, optimizing the concentrations of chemical coagulants applying Central Composed of Rotational Design and evaluating the data via Methodology Surface Response and Global Desirability; and evaluating the effectiveness of the proposed treatment, comparing the optimum dosages determined with laboratory tests. The results indicated that the combination of aluminum sulfate (concentration 0.470 g.L-1) and ferric chloride (concentration 0.115 g.L-1) potentiated treatment, achieving a removal of greywater turbidity of up to 94%; also, thermotolerant coliforms and residual chlorine were reduced, making it possible to reuse them in the discharge of toilets and in irrigation.

摘要 随着水资源需求持续增长且短缺问题日益凸显，亟需开发替代供水来源。为此，本研究聚焦于通过联用硫酸铝（aluminum sulfate）与氯化铁（ferric chloride）两种化学混凝剂（chemical coagulants）优化灰水（greywater）处理工艺，以实现灰水回用。据此，本研究分为三个阶段：对单户住宅洗手池与淋浴产生的灰水开展水质表征；评估以5%溶液配制的硫酸铝与氯化铁联用对灰水的处理效果，采用中心复合旋转设计（Central Composed of Rotational Design）优化化学混凝剂投加浓度，并通过响应面法（Response Surface Methodology）与总合意性（Global Desirability）指标对实验数据进行分析；最后评估所提工艺的处理效能，将实验室测定的最优投加剂量与实际处理效果进行对比。实验结果表明，当投加浓度为0.470 g·L⁻¹的硫酸铝与0.115 g·L⁻¹的氯化铁联用时，可强化灰水处理效果，对浊度的去除率最高可达94%；同时，耐热大肠菌群（thermotolerant coliforms）与余氯含量均得到有效降低，处理后的灰水可回用于马桶冲水与灌溉作业。