The Eeonomic Study Of The Novel Air Flotation-sedimentation Process

The novel air flotation-sedimentation process, is a new combination of water treatmentprocesses, which established by Sun Zhimin and the others of Guangzhou MunicipalEngineering Design and Research Institute, it owns the function of switching two differentprocesses (air flotation and sedimentation) in the same basin. A waterworks of20000m3/d inZhuhai, which was used the novel air flotation-sedimentation process in its modification, waschosen as the research object. We proposed the research methods, from two aspects ofconstruction and operation, to study the process of construction investment, land occupation,operating costs, and evaluate the economy of the process through its yield and recoveryperiod. Then we provided the selection of economical solution in real construction andoperation.Construction economy researching, is a method of comparing the construction fee and landoccupation of a waterworks of20000m3/d in Zhuhai， which used the novel airflotation-sedimentation process in its modification, with three traditional forms of “airflotation+sedimentation” combination basin,"flocculation+horizontal flow settling+flotation" combination basin,"flocculation+tube settling+flotation" combination basin,"flocculation+side flow lamella settling+flotation" combination basin that designed andwaiting to be built. The results showed that the construction fee and land occupation of theformer is less than the latter three. The land occupation of latter three is2.3times,1.4timesand1.7times of the former, respectively; the construction fee of the latter three is1.76times,1.31times and1.40times of the former, respectively.The operation economy researching, is a method that analyses the operating cost of airflotation or sedimentation in different water quality conditions based on the waterworks reports and test data. The results showed that the unit cost of air flotation process was19.41~19.47yuan/km3more than sedimentation process, under the condition of low turbidityand higher algae of raw water; the unit cost of air flotation process was3.65~5.69yuan/km3lesser than sedimentation process, under the condition of middle turbidity and high iron andmanganese of raw water.Financial evaluation is in accordance with the provisions of the relevant documents. And inthe national current fiscal and taxation system and price system, after checking the financialaffairs of a waterworks of20000m3/d in Zhuhai, the results showed that its yield (after tax)is12.67%, its investment payback period (after tax) is10.07years; and its yield (before tax) is16.41%, its investment payback period (before tax) is8.61years.The economy research of novel air flotation-sedimentation has shown a good economy.