Study on household micro-mesh anerobic digester followed by vegetable garden fertilization for resources oriented sanitation of toilet and kitchen

The household three chamber anaerobic digester(3CAD)with its final products being used as fertilizers is the main way for harmless and resourceful treatment of traditional toilet liquids in rural China. When the residents changed their waterless toilets into water-flush toilets, the design volume of the existing 3CADs is far from meeting the requirements of the national mandatory standards regarding the hydraulic retention time (HRT). In this study, a multiple-step micro-mesh anaerobic digester (MMAD) was advanced, aiming to greatly shorten the HRT requirement of the anaerobic digestion. Based on health risk assessment and phytotoxicity assessment of the effluent, the feasibility of MMAD method was verified. According to the results of the comprehensive evaluations, the optimization of the setting parameters of the multi-step micro-meshes and the HRT of the digester were also obtained. Setting four-step micro-meshes with apertures of 150 μm,75 μm,50 μm and 5 μm along the water flow direction, the effluent quality obtained when the HRT is 10 days is as follows: the SS5 (>5 μm) was less than 0.5 mg L−1, representing that the effluent index of parasite eggs was qualified; the fecal coliform value of the effluent was greater than 10−4; the removal efficiency of SS and COD were 82.28% and 67.27%, which were much better than those of the 3CADs. After continuous operation for 236 days, the reactor showed no sign of clogging. The system with MMAD + vegetable garden fertilization can not only meet the needs of modern sanitation in rural areas at low cost, but also help to achieve the goal of carbon peak and neutrality, which are in line with the concept of sustainable development.