Abstract
Compared with conventionally collected sewage, source-diverted greywater has a higher potential for on-site treatment and reuse due to its lower contaminant levels and large volume. A new design of granular activated carbon (GAC) biofilters was developed by incorporating unsaturated and saturated zones in a single stage to introduce an efficient, passive, and easy-to-operate technology for greywater on-site treatment at the household scale. The design was customized for its intended application considering various aspects including the reactor’s configuration, packing media, and feeding strategy. With the highest hydraulic and organic loadings of 1.2 m3 m−2 d−1 and 3.5 kg COD m−2 d−1, respectively, and the shortest retention time of 2.4 h, the system maintained an average total chemical oxygen demand removal rate of 94% with almost complete removal of nutrients throughout its 253 days of operation. The system showed a range of reduction efficacy towards five surrogates representing viruses, bacteria, and Cryptosporidium and Giardia (oo)cysts. A well-functioning biofilm was successfully developed, and its mass and activity increased over time with the highest values observed at the top layers. The key microbes within the biofilter were revealed. Feasibility of the proposed technology was investigated, and implications for design and operation were discussed.
Highlights
Greywater often has lower contaminant levels compared to other wastewater streams because most of the contaminants’ loadings are excluded; further, greywater typically makes up 50–80% of domestic water consumption [1,2]
The results acquired from this study provide insights into the efficacy, functionality, and design of granular activated carbon (GAC) biofilters as a commercially viable treatment technology that can contribute to maximizing water-use efficiency through on-site greywater treatment and reuse
The GAC was efficient in removing surfactants with an efficiency of 98% under optimum conditions
Summary
Greywater often has lower contaminant levels compared to other wastewater streams because most of the contaminants’ loadings are excluded (such as faeces and urine); further, greywater typically makes up 50–80% of domestic water consumption [1,2]. Most of the previous greywater studies have focused on utilizing treatment technologies that have been commonly used in centralized domestic sewage treatment plants. This approach ignores a wide range of potential decentralized applications of greywater reclamation. Greywater is of relatively better quality compared to combine sewage, it has special characteristics that require unique treatment technologies that are customized to these characteristics
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