Research On The Application Of Anaerobic Process In Sanitary Waste Water Treatment

The water resources are quite scarce in China and the per capita quota is only equal to the one quarter of the world average. With the population increase, economy development and rapid urbanization, the situation of water resource shortage will become more serious in the coming years.Over the past decade, a large amount of investment has been spent on the construction of wastewater treatment plants for dealing with the municipal wastewater generated by the cities along the Three Gorges Reservoir. However, many these treatment plants are not in adequate operation due to economic reasons. Appararently, the high expenses on the operation and maintenance of the treatment plants have become the hindrance of municipal wastewater treatment in Three Gorges Region, even the whole country. Therefore, a kind of reliable and economical treatment technology is urgently expected.The development of anaerobic treatment techonolgy of wastewater has gone through many generations, hereinto the UASB(Upflow Anaerobic Sludge Blanket) reactor and the EGSB(Expanded Granular Sludge Bed) reactor are the representatives of the third generation and the forth generation(plug flow reactor); they belong to high-efficiency anaerobic treatment technoloy and work well at treating municipal wastewater of low concentration. However, until now high-efficiency anaerobic treatment techonologies have not been applied in the treatment of municipal wastewater in China.A high-effiency plug flow anaerobic reactor is developed based on the classic anaerobic dynamics model-Monod Equation and analysing the characteristics of plug flow reactor. The pilot experimental study is carried out on the treatment of municipal wastewater by the high-efficiency anaerobic plug flow reactor and meanwhile the impacts of various factors on the treatment efficiency, such as the variation of inluent load, alkalinity, mixing intensity, catalyst, gas generation and temperature, are observed. The results indicate that the influent load has a little influence on the treatment efficiency, and alkalinity is able to keep the wastewater in the range of the requirements of biological growth; however, mixing intensity has an apparent influence on the treatment efficiency, and microelement catalyst and temperature inluence the treatment efficiency largely. It is also found that addition of microeloement catalysts will reduce the adverse impacts caused by the lower temperature.By theoretical deduction, the author elaborates a dynamics model of anaerobic treatment reaction, and takes advantage of the model to predict the COD concentration of the effluent. The calculation results show that the prediction of the model can match the experiment results well with a standard error of below 10%, which indicates the model can simulate the process of the anaerobic treatment reaction of municipal wastewater and could be meaningful for the development of a practical project in the future.Althrough the treatment efficiency is quite ideal, the effluent can not meet the national emmision standards yet. Therefore, some subsequent technologies are still necessary to treat the effluent further. Through comparing the traditional technologues such as CASS(Cyclic Activated Sludge System), Oxidation Ditch, Bilogical Contact Oxidation and Short-distance Nitration etc, the Short-distance Nitration techonology is choosen as the process following the anaerobic treatment technology. Thus, an entire municipal treatment system is formed. The results of the experiments on the treatment efficiency by the system show that the Anaerobic Treatment plus Short-distance Nitration technology combination can produce an effluent that meets the national standards and meanwhile saves an operation expense of 30% compared to the traditional techonologies.