Study On The Mathematics Model And New Technics Of Municipal Sewage Degradation By Outside Cycle Anaerobic Reactor

Anaerobic treatment is a technology of low energy consumption, low construction and operating costs, less sludge output and small layout area. It will be very attractive for some regions of our country, where the climate is amenable. So the subject of the paper is to develop a new type of energy saving process-the Outside Circling Anaerobic Reactor (OCAR). Through small-scale comparative study of the Up-flow Anaerobic Sludge Blanket (UASB), Expanded Granular Sludge Bed (EGSB) and OCAR treating synthetic municipal wastewater, stabilization shock of process operation were investigated, on which effects of factors such as the up-flow velocity, HRT, organic load on OCAR were focused. Characters of municipal wastewater treatment by EGSB and OCAR were studied; furthermore, effects of suspended solids (SS), dissolved oxygen and temperature on OCAR treating municipal wastewater were analyzed; also, residence time distribution (RTD) model, diffusion models and Anaerobic Digestion Model No. 1 (ADM1) were used to analyze the reactor performance.Start-up modes of low-temperature and high-temperature were studied comparatively using seeded granular sludge that has been adapted to the municipal wastewater. Analyses of COD, alkalinity, VFA, Coenzyme F420 and EPS etc indicated that the start speed were in the order of OCAR>EGSB>UASB. With the increasing of flow rate, effluent SS of OCAR was significantly lower than EGSB. When the up-flow velocity was 9.0 m/h , the value of difference reaches its biggest as 58mg/L, which indicated that through separation of effluent and recycled stream before precipitation areas, OCAR can reduce effluent SS significantly. Along with the lower residence time, organic pollutants loads of both OCAR and EGSB increases, when the residence time is 2.08 hr, the organic load reach 3.14 kg COD/(m~3·d), and the effluents meet secondary sewage discharge standards stability; relationship between the organic loading and HRT is: Y=0.26 Ln(x) + 2.13.Hours of continuous experiments showed that substrate degradation of UASB, EGSB and OCAR fit the Monod model.A pilot experiment was established in a municipal wastewater treatment plant, and actual performance of OCAR at room temperature was discussed specifically. As quality of municipal wastewater fluctuated much, The performance of OCAR pilot installations with perforated pipe water distribution system became unstable and effluent COD fluctuated obviously, the transformation used by the high pulsed water distribution system instead of perforated pipe water distribution system inundated, which not only effectively reduced effect of the flow fluctuations on the reactor operation stability, but also improved efficiency of the reactor; with increasing of reflux ratio, effluent SS of EGSB and OCAR gradually increased too. However, effluent SS of OCAR was obviously lower than that of EGSB (with the largest difference of 66.3 mg/L). Even when the reflux ratio increased to 30, effluent COD of OCAR did not change much. SS were high in the municipal wastewater, but can be effectively depredated in OCAR without accumulation in the reactor. OCAR used effluent recycle and higher up-flow rate to make better mixing conditions, strengthening the substrate diffusion and transmission; at the same time it can maintain adequate quantity of sludge in the reactor, which can compensate for the fluctuations of the temperature. As the influent COD of the municipal wastewater was low, adverse effects of low-temperature on anaerobic degradation can be offset.Therefore, temperature fluctuations will not affect the basic operation of the system of OCAR at room temperature treatment of low concentrations of municipal wastewater. DO and SMA of the anaerobic granular sludge fited a good linear relationship of Y =- 2.9885X +90.162 at room temperature; as anaerobic granular sludge has facultative bacteria buildings in the periphery of particles, with timely completion influent consumption of dissolved oxygen, it can play a protective role for particles within the methane-producing bacteria. In the media-temperature processing load IC citric acid wastewater sludge particles for the average particle size 1.337 mm, sludge average size dropped to 1.106 mm in OCAR after inoculation of 30 days, as the organic load and temperature decrease. The study of the reactor control the balance through sludge showed that only when the reactor volume load Y and effluent TSS (X) meet the following relationship, can the reactor maintain sludge balance to maintain the normal operation:In the formula,ηstands for the average removal efficiency of COD, average, y yield coefficient, HRT hydraulic retention time. The longer the granular sludge inoculated, the more SMA of the granular sludge, and the greater the methane-producing bacteria activity is; Along with the increase in volume load, Coenzyme F420 of the granular sludge increased. There were 15 microbial species in the sludge of media-temperature processing citric acid wastewater while 9 of them were eliminated, and six new species were generated from the normal temperature processing municipal wastewater treatment. After treatment at temperature of 10℃, 20℃, 30℃respectively, microbial community structure and population size of the anaerobic granular sludge marked the succession process, PCR-DGGE map similarity coefficient Cs is 53.5% - 74.5%; the greater the temperature difference, the smaller Cs is.RTD models were used to analyze the hydraulic characters of EGSB and OCAR. Discrete parameter D and the dead percentage showed that when the up-flow rate was high, EGSB existed ditch stream with increase of dead percentage; OCAR used a central return, which improved the water distribution system. The higher the velocity increases, the greater the discrete parameter D is, the better the mixed results were. When the up-flow rate rose to 9.00 m/h, the dead zone percentage decreased to 0.87%. Dispersion model was used for different velocity increased under OCAR sludge concentration of simulation, the simulation process, through the inclusion ofthree-phase separator separation efficiency (SE) to achieve the concept of the modelto simulate the effluent SS. Standard deviation of the simulation data was less than 6%.