Viability of a Single-Stage Unsaturated-Saturated Granular Activated Carbon Biofilter for Greywater Treatment

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.

Coupling Microbial Electrolysis Cell and Activated Carbon Biofilter for Source-Separated Greywater Treatment

“…Thus, a further increase in HRT would be required to meet the recommended effluent quality for reuse. However, the results were quite expected based on the previous reports that aerobic biofilter would be effective for greywater treatment [10,17,44,45].…”

“…Interestingly, the GAC biofilter in this study showed effective greywater treatment at shorter HRTs as compared to the previous reports on different biofilter studies for greywater [10,17,44,45]. Based on an extensive literature review, biofilters studied for greywater were operated without any liquid recirculation [8,10,17].…”

“…Among various treatment methods, passive treatment systems like biofilter, constructed wetland, etc., have been reported as a simple and technically efficient method 2 of 11 for greywater treatment [8][9][10][11][12][13]. For instance, a recent study [17] reported a granular activated carbon (GAC) biofilter that could remove 94% chemical oxygen demand (COD) from greywater for a hydraulic retention time (HRT) of 2.4 h. Interestingly, energy recovery potential from greywater with anaerobic biotechnologies has been rarely investigated. Anaerobic bioprocess, such as anaerobic digestion, is usually known to be more effective for high-strength wastewater [18][19][20].…”

Bio-enhanced Granular-Activated Carbon Dynamic Biofilm Reactor for Greywater Treatment: Biofilm Growth, Performance and Mechanisms

“…Various methods, including physical, chemical, biological, and their combined techniques, have been used to treat GW 1,7 . However, these approaches ignored the potential application of decentralized on-site reuse of GW 8 . Traditional aerobic biological treatment technologies can achieve efficient removal of organics and nitrogen 3 , but several shortcomings are still remained.…”

“…Because of the high porosity, large specific surface area and excellent adsorption property, granular activated carbon (GAC) is widely used as the filter media for biological filters in wastewater treatment 13 . In the GAC-based biofilters, GAC media can enable the attachment and growth of biofilm 8 ; as the "pollutants transfer station", GAC can also uptake and store various pollutants that supplying for microbial metabolism 14 , all of which maintain high activity and biochemical reaction rate in the biofilm. GAC biofilters can achieve the efficient removal of pollutants by multiple processes including GAC filtration, adsorption and catalysis 14 , as well as the biosorption and biodegradation in biofilm 15 .…”