【導讀】它包括物理，化學和生物過程，消除物理，化學和生物污染物。是集中產(chǎn)生廢物流以及固體廢物或污泥進行處理或再進入環(huán)境。種污物通常是在無意中受到了許多有毒的有機和無機物的污染。污水是由個人住宅，機關，商業(yè)和工業(yè)機構產(chǎn)生的。所，浴室，淋浴，廚房，水槽廢液等等，這些水將通過污水管排放。在發(fā)達國家，家居分別將污水排放為灰水和黑水已經(jīng)越來越普。遍，因為灰水可以用于澆灌植物或回收用來沖馬桶。因此城市廢水包括住宅，商業(yè)和工業(yè)排放的廢水，且可能包括雨水徑流。具有處理雨水能力的污水處理系統(tǒng)被稱為合流排水系統(tǒng)。因為它們復雜化而且由于其季節(jié)性，降低了污水處理廠的效率。此外，當遭遇暴雨時，過量的。由于降雨流經(jīng)屋頂和地面時，會帶走包括土壤顆粒和其他沉積物，重金屬，有機物，動物排泄物，污油和油脂等各種污染物質。收集和處理，通常取決于當?shù)刂莺吐?lián)邦法規(guī)和標準。生物膜處理法和停止增長生物處理法。會導致介質堵塞和濾池上表面積水。

　　

【正文】 eved in a single reactor while nitrate conversion occurs in anoxic mode. BAF is operated either in upflow or downflow configuration depending on design specified by manufacturer. Membrane bioreactors Membrane bioreactors (MBR) bine activated sludge treatment with a membrane liquidsolid separation process. The membrane ponent uses low pressure microfiltration or ultra filtration membranes and eliminates the need for clarification and tertiary filtration. The membranes are typically immersed in the aeration tank。 however, some applications utilize a separate membrane tank. One of the key benefits of an MBR system is that it effectively overes the limitations associated with poor settling of sludge in conventional activated sludge (CAS) processes. The technology permits bioreactor operation with considerably higher mixed liquor suspended solids (MLSS) concentration than CAS systems, which are limited by sludge settling. The process is typically operated at MLSS in the range of 8,000–12,000 mg/L, while CAS are operated in the range of 2,000–3,000 mg/L. The elevated biomass concentration in the MBR process allows for very effective removal of both soluble and particulate biodegradable materials at higher loading rates. Thus increased Sludge Retention Times (SRTs) — usually exceeding 15 days — ensure plete nitrification even in extremely cold weather. The cost of building and operating an MBR is usually higher than conventional wastewater treatment. Membrane filters can be blinded with grease or abraded by suspended grit and lack a clarifier39。s flexibility to pass peak flows. The technology has bee increasingly popular for reliably pretreated waste streams and has gained wider acceptance where infiltration and inflow have been controlled, however, and the lifecycle costs have been steadily decreasing. The small footprint of MBR systems, and the high quality effluent produced, make them particularly useful for water reuse applications. There are MBR plants being built throughout the world, including North Librty, Iowa, Georgia, and Canada. Secondary sedimentation The final step in the secondary treatment stage is to settle out the biological floc or filter material and produce sewage water containing very low levels of organic material and suspended matter. Rotating biological contactors Main article: Rotating biological contactor Rotating biological contactors (RBCs) are mechanical secondary treatment systems, which are robust and capable of withstanding surges in organic load. RBCs were first installed in Germany in 1960 and have since been developed and refined into a reliable operating unit. The rotating disks support the growth of bacteria and microorganisms present in the sewage, which breakdown and stabilise organic pollutants. To be successful, microorganisms need both oxygen to live and food to grow. Oxygen is obtained from the atmosphere as the disks rotate. As the microorganisms grow, they build up on the media until they are sloughed off due to shear forces provided by the rotating discs in the sewage. Effluent from the RBC is then passed through final clarifiers where the microorganisms in suspension settle as a sludge. The sludge is withdrawn from the clarifier for further treatment. A functionally similar biological filtering system has bee popular as part of home aquarium filtration and purification. The aquarium water is drawn up out of the tank and then cascaded over a freely spinning corrugated fibermesh wheel before passing through a media filter and back into the aquarium. The spinning mesh wheel develops a biofilm coating of microorganisms that feed on the suspended wastes in the aquarium water and are also exposed to the atmosphere as the wheel rotates. This is especially good at removing waste urea and ammonia urinated into the aquarium water by the fish and other animals.