Membrane Bioreactor technology for the treatment and reuse of mixed domestic wastewater from residential areas

Abstract:

In many Chinese residential communities, reclaimed water reuse system meet the problem of long-term application for the poor water quality and sensory discomfort. Aimed to meet the “Standard of Urban Wastewater Reuse” for miscellaneous water consumption (GB/T 18920-2002) and scenic environment use (GB/T 18921-2002), a pilot-scale Anoxic/Oxic Membrane Bioreactor (AO-MBR) followed by activated carbon filter and ultraviolet combined chlorine disinfection devices were installed to treat the mixed domestic wastewater in a residential area in north China. The objectives of the research were to investigate the reclaimed water qualities and optimize the main operating parameters; furthermore, to analyze the technical and economic suitability for treatment of the mixed domestic wastewater with grey water only. The results showed that, when the mixed domestic wastewater (effluent of septic tank) was chosen for treatment, under the conditions of Hydraulic Retention Time (HRT) 8h, mixed liquor suspended solids (ρMLSS) 3500~7500 mg•L-1, the effluent was colorless and odorless, the chemical oxygen demand (ρCOD), Biochemical Oxygen Demand(ρBOD5) and ammonia nitrogen(ρNH3-N) was respectively below 30 mg•L-1, 3 mg•L-1 and 3.0 mg•L-1, which can stably meet the “GB/T 18920-2002”, however, the total nitrogen(ρTN) and total phosphorus(ρTP) concentration of effluent can’t meet the requirements of “GB/T 18921-2002”; While simulating the ρCOD: ρTN: ρTP ratio of the raw wastewater (influent of septic tank), under the conditions of HRT 10 h, SRT 50 d, the recycling ratio 200%, ρMLSS 5500~6000 mg•L-1, the dosage of poly-aluminum chloride(ρPAC) 4~5 mg•L-1, the effluent quality was better than the “GB/T 18920-2002” and the “GB/T 18921-2002”. To achieve the same reclaimed water quality, the mixed domestic wastewater treating process is more complicated than that of the grey water, at the same time, the operating cost is 0.32 Yuan•m-3 higher than the later. Therefore, from the views economic and technical feasibilities, it should be taken into account the demand and potential usage of the reclaimed water, the local climate conditions during selecting a suitable wastewater collecting and treating system in residential areas.