The standard specifies the pollutant limits for the effluent of urban wastewater treatment plants, waste gas emissions and sludge disposal (control).
The standard applies to the management of urban sewage treatment plant effluent, exhaust emissions and sludge disposal (control).
Residential neighborhoods and industrial enterprises within the independent domestic sewage treatment facilities pollutant discharge management, also in accordance with this standard.
The question said to improve should refer to how the water quality can be treated to provide efficiency it. General sewage treatment plant treatment has the following five methods:
One, intermittent activated sludge method (SBR)
Intermittent activated sludge method, also known as the sequencing batch activated sludge method (Sequencing Batch Reactor-SBR), which consists of single or multiple SBR tanks, operation, wastewater batches into the pool, in order to go through five independent stages, namely Intake, Reaction, Sedimentation, Drainage and Idle. Water intake and drainage with water level control, reaction and precipitation with time control, the time of an operating cycle according to the load and water requirements vary, generally 4 to 12h, of which the reaction accounted for 40% of the effective pool volume for the cycle of water intake and the required volume of sludge and the sum of the volume.
Response faster than the continuous flow method, high treatment efficiency, load impact resistance; due to the high concentration of substrate, the concentration gradient is also large, alternating anoxic, aerobic state, can inhibit the excessive propagation of specialized aerobic bacteria, is conducive to the biological denitrification and removal of phosphorus, but also due to the short age of the mud, the filamentous bacteria are unlikely to become the dominant, so that the sludge is not easy to expand; compared with the continuous flow method, the SBR method, the short flow Compared with the continuous flow method, the SBR method has a short process, simple structure of the device, when the water volume is small, only one intermittent reactor is needed, there is no need to set up a special sedimentation tank and adjustment tank, no need for sludge reflux, and the operation cost is low.
Two, adsorption regeneration (contact stabilization) method
This way to make full use of the initial removal capacity of activated sludge, in a relatively short period of time (10 ~ 40min), through the adsorption to remove the wastewater in the suspended and colloidal organic matter, and then through the liquid-solid separation, wastewater that is to obtain the purification of the BOD5 can be removed by about 85% ~ 90%. Adsorption of saturated activated sludge, part of the need to return to the flow, introduced into the regeneration tank to further oxidative decomposition, to restore its activity; the other part of the remaining sludge without oxidative decomposition that is discharged into the sludge treatment system.
Separately in the two pools (adsorption pool and regeneration of his) or in the same pool of the two sections. It adapts to the load impact of the ability to be strong, but also eliminates the initial sedimentation tank. The main advantage is that it can greatly save infrastructure investment, most suitable for dealing with wastewater containing more suspended and colloidal substances, such as tannery wastewater, coking wastewater, etc., the process is flexible. However, due to the short adsorption time, the treatment efficiency is not as high as the traditional method.
Three, oxidation ditch
Oxidation ditch is a special type of delayed aeration method, it's like a runway plane, trench set two aeration brush (disk), but also with surface aerators, jets, or lifting tube aeration device. Aeration equipment work to promote the rapid flow of ditch liquid, to achieve the role of oxygen supply and mixing.
Compared with the ordinary aeration method, oxidation ditch has the advantages of capital investment, maintenance and management is easy, stable treatment effect, good quality of effluent water, sludge production is less, there is a better de-N, P role, adapt to the load impact capacity and so on.
Four, continuous feed cycle cycle delayed aeration activated sludge method (ICEAS)
ICEAS reactor with pre-reaction area in front (10% of the pool volume). The reactor consists of a pre-reaction area and a main reaction area, and realizes continuous water intake and intermittent drainage. Pre-reaction area is generally in anaerobic and anoxic state, where organic matter is adsorbed by activated sludge, which also has the role of biological selection to inhibit the growth of filamentous bacteria and prevent sludge expansion. The adsorbed organic matter is oxidized and decomposed by activated sludge in the main reaction area.
Reaction of continuous water intake, to solve the incoming water and intermittent water intake does not match the contradiction. However, this process has poor sedimentation effect, deterioration of purification effect, easy sludge expansion, low sludge load, long reaction time, increased equipment volume, and larger investment.
Fifth, biological denitrification and phosphorus removal process (A / A / O)
Wastewater first into the anaerobic pool and return sludge mixing, in the role of parthenogenetic anaerobic fermentation bacteria, wastewater in the biodegradation of macromolecules can be converted to polyphosphorus bacteria can absorb the small molecules of organic matter (eg, VFA), and in the form of PHB stored in the body, and the energy required from the decomposition of polyphosphorus chain. Subsequently, the wastewater enters the anoxic zone, denitrifying bacteria use the organic substrate in the wastewater to denitrify the NO3- brought in with the reflux mixture. When the wastewater enters the aerobic tank, the concentration of organic matter in the wastewater is low, and the polyphosphorus bacteria mainly obtain energy through the decomposition of PHB in the body for bacterial proliferation, while the dissolved phosphorus in the surrounding environment is absorbed into the body and stored as polyphosphorus chains, which is subsequently discharged from the system in the form of residual sludge. The lower concentration of organic matter in the aerobic zone of the system is favorable for the growth of autotrophic nitrifying bacteria in this zone.
Anaerobic, anoxic, aerobic three different environmental conditions and different types of microbial flora of organic cooperation, can simultaneously have the removal of organic matter, denitrification and phosphorus removal function; process is simple, hydraulic retention time is shorter; SVI is generally less than 100, will not occur sludge expansion; sludge in the phosphorus content is high, generally more than 2.5%; anaerobic-anoxic pool only need to be stirred gently, so that mixing, and to not increase the dissolved oxygen. And do not increase the dissolved oxygen to the degree; sedimentation tank to avoid anaerobic - anoxic state, to avoid the release of phosphorus polyphosphate bacteria to reduce the effluent water quality and denitrification to produce N2 and interfere with the sedimentation; denitrification effect by the size of the mixture of reflux than the effect of phosphorus removal effect by the reflux of sludge with the impact of DO and nitrate oxygen, and thus denitrification and removal of phosphorus is not possible to improve the effect.