Technical And Economic Analysis Of Semi-centralized Greywater Treatment And Reuse System

Based on fundamental data from the Chinese residential aera (Shanghai and qingdao), we proposed the concept of "Semi-centralized supply and treatment systems". In this paper, the concept is applied to analyze the economical and techinical feasibility of the greywater treatment and reuse system in Chinese residential area. Alike the prototype, the so-called supra cell is developed based on data from shanghai residential aera, which covers an area of 500,000 m² and includes 11,520 inhabitants. From the technical and economical point of view, the simulation of the investment and operation cost on such semi-centralized greywater reuse system is performed in order to determine its appropriate size for Chinese residential aera.The result shows that the specific investment cost of pipeline for one supra cell is 4424 yuan/Cm³.d^-1), while the specific investment costs of the corresponding greywater treatment process of IMBBR(Integrated Moving Bed Biofilm Reactor), BAP(Biological Aerated Filter) and MBR(Membrane Biological Reactor) are 3558, . 3627 and 5224 yuan/(m³.d^-1), respectively. The specific investment cost of pipeline increases with the number of supra cells, whereas the specific investment cost of treatment process is the opposite: when the scale reaches 4 supra cells, the specific cost of pipeline and the two treatment processes are respectively 4607,2362,2154 and 4134 yuan(m³.d^-1).With comparison to the decentralized traditional "cluster" and "on-site" treatment system, "semi-centralized greywater treatment and reuse system " is confirmed to be more suitable for Chinese residential area.Finally, through the calculation on investment and operation cost of pipeline and treatment plant along with the influence of water price on investment payback period, the simulation indicate that in the shanghai region, the optimal size of semi-centralized greywater reuse system is between 4 and 8 cells, i.e. the treatment capacity between 3000 and 6000m³/d which correspond to 50,000 and 10,000 inhabitants. In such scale, the opearation costs of MBBR,BAF and MBR are approximately 0.59,0.62 and 0.67 yuan/m³(depreciation cost not included), whereas if the depreciation cost is considered, the costs are 1.8,1.8 and 2.7 yuan/m³ respetively, the corresponding investment payback period are 12 and 16 years respetively. While in north China region, over 1 cell is believed to be appropriate, but bewteen 4～8 cells is also confirmed to be optimal, in such sacle, the investment payback period of the two treatment process are 6 and 8 years respectively.