Technical Analysis And Economic Comparison Of The Projects To Treat The Sewage In Small Towns

The small towns are essential in the sustainable development, which can affect the urbanization in China. At present, waters are polluted severely by the wastewater from small towns. Therefore, the technical analysis and economic comparison of the process to treat the sewage in small towns are necessary. Based on the financial and natural conditions and the scale of the wastewater treatment in small towns, Oxidation Ditch, Anaerobic-Anoxic-Oxic(A/A/O), Sequencing Batch Reactor(SBR) and Bio-contact Oxidation Process are chosen as the suitable processes to treat wastewater.When the scales of wastewater treatment plants are defined as 0.25 × 104m3/d, 0. 5 × 104m3/d 1 × 104m3/d, 2 × 104m3/d, and the plants are with the same characters of raw wastewater, the mathematical models of the investment and operational cost with the treatment scale are put forward for the four processes.Four processes are evaluated comprehensively with analytic hierarchy process. The results are as follows: (1) When the scale is 2× 104m3/d, the best process is SBR, the second is A/A/O, the third is Oxidation Ditch, the last is Bio-contact Oxidation Process. (2) When the scale is 1 × 104m3/d, the best process is SBR, the second is A/A/O, the third is Bio-contact Oxidation Process, the last is Oxidation Ditch. (3) When the scale is 0.5 × 104m3/d, the best process is SBR, the second is A/A/O, the third is Oxidation Ditch, the last is Bio-contact Oxidation Process. ?When the scale is 0.25×104m3/d, the best process is Bio-contact Oxidation Process, the second is SBR, the third is Oxidation Ditch, the last is A/A/O.The mathematical models and the results of technical analysis and economic comparison are helpful for the construction of the treatment plants in small towns in China.