Research On The Centralized Sewage Treatment Plant In Constructed Wetland Treatment

In a word, nowadays, the primary treatment object of wastewater treatment factory of citiesinclude mainly to dispose organic(COD, BOD5),suspended solid(SS) and nitrogen,phosphorus, etc.Although the majority of secondary biological treatment may reducepollutants in the water, but their emissions are greatly.Large quantities of phosphate present inwastewater is one of the main causes of eutrophication, so it’s very important to control thecontent of phosphorus in effluent.On the other hand,shortage of water resource becomesincreasingly serious, and the regeneration and reuse of the sewage is one of the effective wayto solve shortage of water resource.and it has economic benefits, social benefits and ecologicbenefits. Furthermore, it can meet the requisition of living and industry.In order to improve the water quality of receiving waters environment quality, and access tohigher quality back into the water, the depth of the secondary effluent still need furthertreatment. According to the raw water quality of sewage (waste) and requirements quality oftreated water,it can be use tertiary treatment or multistage process to remove lowconcentration of COD, BOD and SS in water and nitrogen and phosphorus nutrient salts. ASthe large scale of sewage treatment plant of tail water water about tens of thousands of squareper day,it is not too realistic to use membrane separation, advanced oxidation process, andCW technology has less investment, low energy consumption, stable discharging water,impact resistance ability, line with current situation in China, so it is one of the best choice ofthe in tail water treating.Removal of Phosphorus wetland mainly by adsorption of wetland substrate, so screeningsuperior substrate wetland for the construction of wetlands are particularly important.Constructed wetlands to remove nitrogen mainly rely on ammonification, nitrification anddenitrification microorganisms. Where nitrification is mainly carried out in the aerobic environment, and denitrification is carried out in an anaerobic environment. Due to structurecommon constructed wetland can not provide both aerobic and anaerobic environments, sothe total nitrogen removal is often not high. The actual wetlands project, constructed wetlandare prone to clogging, reducing its water purification function.So it is important todeterminate the clogged of wetland systems for rectification and restoration of wetlands.This study used wetlands a matrix material, screened superior filler, and then constructwetlands with the filler, and to optimize wetlands structure and process, to build suitable CWto treat level A emissions standard sewage treatment plant tail water. And analysis theplugging problems of wetlands,then establish a measure method suitable for wetlandsclogging.The major findings were as following:1. Volcanic and activated carbonwere with smallerpenityof0.74g/cm3and0.58g/cm3, advolcano with porosity of77%.Both Freundlich and Langmuir isotherms could adequatelypredict the adsorption process. The maximum adsorption capacities of phosphorus estimatedfrom the Langmuir isotherm, ranked as:(1512mg/g）> anthracite（1144mg/g）> crushed stone（1081mg/g）> activated carbon（975mg/g）> grave（l906mg/g）> zeolite（.880mg/g）> brokenbricks （773mg/g）> volcanic （729mg/g）> blast furnace slag （583mg/g）> sand（454mg/g）.Pseudo second order kinetics could be suitable to describe adsorptioncharacteristics of five substrate including anthracite, bio-ceramic, activated carbon、brokenbricks, blast furnace slag.The process of adsorption could be divided into fast，middle andslow stages.Volcanic is one of the better choices as CW Substrates. Bio-ceramic andanthracite show high ability of phosphorus removal hinted can be used as the substrate oflarger load constructed wetlands.2. DO is uneven distribution in traditional structure, and the purification efficiency is nothigh. In this paper, different structures creating different oxygen environments within thewetland, the results showed that dissolved oxygen is very different for different wetlandspurification efficiency; optimum operation is within the system can be both adequatenitrification the role of aerobic zone, there may be anaerobic denitrification zone. Runningprocess also has a great impact on the purification efficiency, especially for TN removal.3. Developed a portable hydraulic conductivity detector, and establish a simple operation, high accuracy measure methods about clogging in constructed wetland.