Chengdu sewage treatment plant detailed process

Water treatment process: the process is anaerobic or micro-oxygen contact mixing, short-term aeration, separation, aerobic starvation sludge reflux or SBR direct water intake and other processes, so that the original wastewater and aerobic starvation sludge full contact mixing, short-term aeration, settlement and separation; settlement and separation of the supernatant that is the treated effluent, settlement and separation of sludge, most of the sludge, in the aerobic conditions to make it starvation, starvation of sludge and then the original The remaining part is the residual sludge discharge. Process system, mainly consists of AC pool, AeT pool, AS pool, AeS pool connected in sequence The monitoring and control system of wastewater treatment process consists of four parts: model, sensor, local regulator and upper monitoring strategy. Among them, the sensor is the weakest, but also the most important and basic part of the monitoring and control system of the wastewater treatment plant. Increasingly stringent sewage discharge standards have led to the complexity of sewage treatment processes and equipment, the performance of sensors used for monitoring and control of sewage treatment processes has also put forward higher requirements, promoting the development of sensor technology in the field of wastewater treatment, and a number of new types of sensors suitable for wastewater treatment processes have been introduced. Wastewater treatment process is a complex biochemical reaction process, involving a wide range of instrumentation, most of the sensors are unique to the wastewater treatment process, respectively, applied to different occasions, reflecting one or more specific variables in the state of information changes. Wastewater treatment process generally consists of mechanical treatment, biochemical treatment and chemical treatment, which involves liquid phase, solid phase, gas phase three material components. Monitoring these phases of the instrumentation can be simply divided into two categories of general-purpose and special. 2, general-purpose instrumentation of the sewage treatment process General-purpose measuring instruments include temperature, pressure, level, flow, pH, conductivity, suspended solids and other sensors. ① anaerobic digestion process is often implemented due to temperature control, temperature sensors become more important. Typical temperature measurement elements are RTDs ② Pressure measurement is often used as an alarm parameter for aeration and anaerobic digestion processes. ③Level measurement is used for water level monitoring, usually using buoys, differential pressure transmitters, volume measurement, ultrasonic water level detection and other methods of measurement. ④The flow monitoring instruments mainly include Kanban plate, rotor flowmeter, turbine flowmeter, target measuring tank, electromagnetic flowmeter, ultrasonic flowmeter and so on. ⑤ pH is an important variable in the biochemical process, moreover, it is the key value of anaerobic digestion and nitrification process. pH electrodes are usually installed in wastewater treatment plants to immerse in sludge, and long-term maintenance-free can be realized through different cleaning strategies. For wastewater with a high buffering capacity, pH measurements may not be sensitive to process variations and are therefore not suitable for process monitoring and control, in which case a carbonate measurement system can be used instead. (vi) Conductivity sensors are used to monitor changes in the composition of the influent water and also form the basis of the chemical phosphorus removal control strategy. (vii) Traditional biomass measurements are based on the scattering of incident light by suspended particles and the estimation of absorbance. With the advent of sensitive light detectors, sensors capable of automating light effect measurements were introduced. Most commercial sensors use a light source that emits low visible or infrared light in a region where most media exhibit low absorbance. The biomass concentration can also be determined from the difference in velocity of the ultrasound in the free solution between the suspended material and the microorganisms. 3, Sensors in Anaerobic Digestion Processes Measurement of biogas flow is widely used in anaerobic digestion processes to indicate the overall activity of the reactor. In recent years a number of specialized techniques have been used to monitor gas composition. Typical laboratory methods are wash bottle separation methods, where gas composition can be determined based on the ratio of the flow rate before entering the bottle and after exiting the bottle. For example, an alkali flask will be able to collect all the C02, H2S and allow CH4 to pass through. More specialized gas analyzers can directly monitor the gas composition content, such as infrared absorption meters to determine C02 and CH4 content, and specialized hydrogen analyzers have been developed based on chemical power sources. Gas phase H2S meters can determine H2S content by monitoring the reaction of sulfide to lead stripping. The main problem with monitoring systems based on gas analysis is that they cannot directly predict the concentration of the corresponding gas in the liquid phase. Immersion sensors that can directly measure dissolved hydrogen have been developed. Fuel cells are the core of such sensors. direct measurement instruments for H2S and CH4 have not been reported so far. pH measurements are not easy to detect in unbalanced anaerobic digesters, especially when the alkalinity of the mixed liquor is high. Measurements of C02 and carbonate in the mixed liquor can be made in this case. Alkalinity is largely dependent on the carbonate buffer and is therefore often used in control strategies for anaerobic digestion. Carbonate monitors have been developed for use in practical anaerobic digestion processes. There are two basic principles for estimating carbonate alkalinity. One is titration, where advanced on-line titration sensors can simultaneously monitor different components such as ammonia and carbonate. Another method for on-line determination of alkalinity is based on the quantification of gaseous C02 obtained by acidification of the sample. A gas flow meter can be used to measure the volume of the gas produced. All biological activities can be characterized by the production of heat. Measurement of heat by a calorimeter provides direct insight into biological process changes. Flow calorimeters are preferred for wastewater treatment processes.