Study On Debugging And Running Of Wastewater Treatmeat For Small Cities And Towns About Biological Enhanced Flocculation Combined Process

The sewage in small towns is mainly domestic sewage with small water quantity and large fluctuations in water quality.Small towns have these characteristics: complex geology and landform, dispersive population, laggard economy and culture relatively. So they always face the dilemma that the funds are used for Sewage treatment,sewage collection system is not perfect, combined sewers, laggard equipments and lack of professional managers to run in wastewater treatment plant. All along, it is a difficult selection of sewage treatment process, because the requirements of environmental protection are higher but the costs of initial investment and operation and maintenance are less. Combined with the specific situation of small towns,it is imperative to empolder a new suitable sewage treatment technology with higher pollutant removal efficiency,less investment costs, high-efficiency and low-power.Enhanced Bio-flocculation Combined Process which integrated the advantange of biological flocculation and adsorption and biofilm has such characteristics: no need to add chemicals,fast start-up, a certain effect of nitrogen and phosphorus removal, high efficiency, small area, low cost and easy management ,good practicability and superiority and so on.The experiment was carried out in the Jiuxian Town Wastewater Treatment Plant of Tongliang county in Chongqing , which mainly treated domestic sewage with combined sewers. The desigened quality of the effluent can reach grade - one standard B of "Discharge Standards of Pollutant for Municipal Wastewater Treatment Plant "(GB18918-2002). The study included the cultivation of activated- sludge,the start-up of variable rate biofilter ,the optimization studies of combined parameters in combined process 1 and combined process 2 in work condition,as well as the effects of treatment in high-load conditions. Finally, the project's economic and social benefits were analyzed.The wastewater treatment plant cultivated sludge with inoculation and start up of variable rate biofilter with"Quickly Discharge Sludge and Start-up". The start up of plant was finished in 15 day. Advantages of inoculation and Quickly Discharge Sludge and Start-up are start up fastand effective. The conclusions of the study as follows:Combined process 1 : The temperature of Sewage was 21.3℃～25.7℃, MLSS=3000～3500mg/L,the sludge load Ns=0.223～0.313kgCOD/(kgMLSS?d),the fun operated 45 min and stoped 15 min, the air-water ratio was 3.2:1; the flow of sewage treatment was 240m3/d, the percent recycle of sludge was 25%, the influent of CODCr , NH3-N, TN, TP were 212, 31.40 ,34.00 and 2.17mg/L, respectively,and the turbidity was 146NTU . The effluent of CODCr , NH3-N, TN, TP were 21, 0.38,5.23 and 0.97mg/L, respectively,and the turbidity was 0.766 NTU. The average removal rates of CODCr, NH3-N, TN, TP and turbidity were 90.09%, 98.79%, 84.62%, 55.30% and 99.48%, respectively, which were better than the latest grade - one standard B of "Discharge Standards of Pollutant for Municipal Wastewater Treatment Plant "(GB18918-2002).Combined process 2 :The temperature of Sewage was 13.4℃～20.7℃,MLSS=2800～3200mg/L,the sludge load Ns=0.313～0.448kgCOD/(kgMLSS?d),the fun was continuous operation, the air-water ratio was 4.2:1; the flow of sewage treatment was 260m3/d, the percent recycle of sludge was 25%, the influent of CODCr , NH3-N, TN, TP were 262, 22.20 , 31.04 and 1.19mg/L, respectively,and the turbidity was 184NTU. The effluent of CODCr , NH3-N, TN, TP were 38, 4.46, 13.52 and 0.57mg/L, respectively,and the turbidity was 0.913NTU. The average removal rates of CODCr, NH3-N, TN, TP and turbidity were 88.03%,81.22%,60.10%,65.58% and 98.62%, respectively,which were better than the latest grade - one standard B of "Discharge Standards of Pollutant for Municipal Wastewater Treatment Plant "(GB18918-2002).The effluent quality met the designed discharge standards in conditions of combined process 1 and 2. The effluent quality of biological enhanced flocculation combined process of variable rate biofilter and combined process 2 of constructed wetlands met grade-one standard B of "Discharge Standards of Pollutant for Municipal Wastewater Treatment Plant "(GB18918-2002).The combined process can meet the similar situation of small towns sewage treatment requirements and had a strong adaptability. Therefore, in the promotion and use of the process, small towns can choose process according to specific conditions.Backwash cycle of variable rate biofilter in Enhanced Bio-flocculation Combined Process was 5~7d.The results of industrial test showed that the energy cost of the biological enhanced flocculation combined process for 1 m3 wastewater is 0.2092kWh/m3.Advantanges of Enhanced Bio-flocculation Combined Process were high-efficiency,strong ability of resist concussion, steady effluent, low running energy, less excess sludge production, small area, low cost, low operating costs, easy maintenance and management ,the better effect of landscape.This process applies to small cities and towns with small area, high concentrations of wastewater quality, complicated components.Recommended small town sewage treatment process the second choices, as the combined process can be asked to deal with the water management requirements at the same time lower its operation.The study recommend the combined process 2 wastewater treatmeat for the small cities and towns, because its quality of the effluent can reach the desigened value and its operation and management demand is lower.