污水處理廠主要處理單元介紹
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污水處理廠主要處理單元介紹
(一)進流抽水站 本廠處於園區地勢最低處，廠區設施依地勢建造，整體流程採重力之方式設計，進流抽水站位於污水處理廠之最前端，其最主要之功能係以污水泵將進流水揚升後，再以重力流之方式流至後續處理單元進行處理。 (二)機械攔污柵 機械攔污柵主要功能為藉攔柵阻流攔除之作用，可將進流廢（污）水中較大型之固形物，例如：樹葉、樹枝、破布、衛生用品、瓶罐、塑膠袋、垃圾等攔下後清除，其作用可避免後續處理設施中設備(如抽水機，括泥機等)之磨損或量測設備之誤差，尤其是抽水泵之磨損。 (三)巴歇爾量水槽 巴歇爾量水槽是最為被廣泛應用在廢水流量量測之計量裝置，其同時也被安裝在污水處理廠進、放流水明渠渠道中以正確掌握進放流廢水量。其量測原理係藉由污水流經特殊構造之巴歇爾水槽明渠渠道中，因流量之不同產生水位變化，再由超音波量測液位後換算流量值。流量計量設施之正確的使用、選擇、維護及校正對一有效率操作營運管理之現代化污水處理廠是非常重要；流量計需定期委由經授權機構進行校正以確保流量功能正常及讀值正確。 (四)渦流式沉砂池 渦流式沉砂池係屬於污水處理廠前處理設施之一,通常設置於攔污柵之後初沉池及調勻池之前，可避免砂礫於後續管線及池底中沉積造成阻塞亦可減少後續處理單元之機械設備磨損，延長設備使用壽命。一般常見沉砂池的種類有矩形水平流式,曝氣式及渦流式等三種。渦流式沈砂池係圓形形狀池體，其沉砂原理為污水沿池邊緣以切線方向流入，沈砂池中心設有葉片攪拌器可控制並保持水流定速旋轉，產生離心式水流使砂礫沈降於中央下部之貯砂斗內，而有機物則懸浮不致沈降，沉砂再經抽砂泵或氣升泵抽出送至洗砂分離器，利用廢水洗砂分離後，廢砂再由清運車定期清運至合法處理機構進行掩埋或再利用。 (五)調勻池 進流之廢（污）水其水質或水量一般皆處於不穩定之變動狀態，為使後續處理單元之操作成效穩定，尤其是針對較敏感之生物處理單元，過劇之水質酸鹼變化或毒性物質等，皆可能造成微生物受到明顯抑制或死亡，影響處理效率，或者造成化學處理之加藥無法有效穩定控制，因此必須在前端處理單元設置有一適當體積之空間，調整變化之進流水質與水量，及有足夠之停留時間藉由曝氣攪拌調勻污染物濃度變化，同時預先增加廢（污）水中之溶氧，可利後續之生物處理程序。 (六)接觸氧化池 好氧生物處理法主要被應用於去除廢水中有機物，該有機物常以生化需氧量(簡稱BOD5)量測及表示。接觸氧化池為一固定膜式好氧生物處理法，附著性生長之微生物生長於具有高比表面積蜂巢式濾材上，以鼓風機將空氣注入廢（污）水，提供微生物所需之溶氧(一般DO值介於1.0~3.0 mg/L)，藉由微生物分解有機物之作用，消耗水中之有機成分。 固定膜式生長之微生物因其不會被大量洗出，使得生物有較長時間於池內生長，因此從細菌、原生動物到後生動物皆常出現，生物相種類及數量相當豐富，對於環境有相當之適應性，於污染負荷之衝擊適應性較懸浮生長之微生物強，且操作管理簡單，適合於工業廢水之處理，但操作上有可能造成污泥累積阻塞接觸濾材之缺點，因此適當定期之反沖洗是操作上重要之一環。 (七)化學混凝沉澱池 化學混凝作用係藉由加入之混凝劑及膠凝劑，破壞水中膠體物質或不易沉降之細小懸浮固體物粒子間之穩定狀態，再由產生膠凝作用增加顆粒大小，以沉降方式將其去除，本廠之設計為污水先經快混槽加入混凝劑多元氯化鋁(PAC)由快速攪拌機進行快混，以打破細微顆粒之穩定性使顆粒得以互相碰撞而增大，再經兩段慢混槽，藉由加入陰性高分子聚合物助凝劑(Polymer-)以慢速攪拌機作用增加其粒子與粒子間之接觸架橋機會，產生較大顆粒之化學混凝膠羽後進入矩形沉澱池，使混凝膠羽沉降於池底，以去除廢（污）水中之污染物。 (八)砂濾池 砂濾單元設置在生物及化學處理單元之後以進一步去除放流水中部分懸浮固體勿(SS)及附著於固體物之BOD5。 砂濾為一種固體與液體分離之程序，藉由沈澱、凝聚吸附及攔截阻流等作用去除含在廢（污）水中之粒子；濾料對於粒子的去除機制作用如下: (1) 沉澱作用:藉由粒子於濾料粒子間之沉澱以達過濾之 效果，惟過濾水質受沉澱面積（濾料之表面積）之 大小影響，濾料之表面積越大，處理水之水質越好。 (2) 凝聚吸附作用:粒子附著於濾材表面上，而被捕捉。 粒子藉由物理、生物、化學之凝聚作用，而達到過 濾之功能。惟過濾水之水質受濾料之接觸機會所影 響，濾層越厚、粒徑越小濾材表面積越大，粒子抑止效果越佳，過濾效果也越高。 (3) 攔截阻留作用:為較濾材之濾粒間隙為大的粒子，被 濾材所捕捉。 通常過濾以(1)及(2)之作用較大，阻留作用則為上 述之副作用。 砂濾單元包括過濾及反沖洗二個程序，連續反覆循環操作，反沖洗過程可將濾料清洗乾淨。當砂濾出流水SS出現超過可接受之過高(穿透)現象時或濾床前後壓損增加到極限值，即表示過濾濾程已結束需進行反沖洗程序以移除附積在砂床間之懸浮固體物；反沖洗所產生的廢水則迴流至污水廠前處理設施後再次進行生物及化學處理。
(九)AO+MBR處理系統
AO-MBR為一種生物處理單元，包含缺氧池、好氧池、膜濾池，其可取代 (十)污泥處理系統 本廠之污泥來源包括化學性及生物性污泥及少量各沉澱池所收集之浮渣等，由泵浦抽送至污泥濃縮池，將含水率高約98%~99%之污泥濃縮使其含水率降低至約95%左右，經由濃縮後之污泥再進入污泥貯槽，然後加入高分子聚合物(Polymer+)調理，再進入帶濾式脫水設備將污泥脫水，使其含水率大幅降低至約80％以下，最後經由螺旋式輸送機輸送至污泥餅暫存槽內，後再行委託合格之污泥清除商將污泥清運至處理廠再利用或最終處置。
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Introduction for major units of wastewater treatment plant Generally, the wastewater relies on the force of gravity to flow from factories to the wastewater treatment plant by sewage pipes. So the plants are planned and located on the park’s site of lower ground level. Once, the wastewater enters into the plant at the first point, the pumping station is built up for lifting the influent up to the next treatment facilities and then wastewater flows to the following units by gravity. (2) Mechanical bar screens In wastewater treatment, bar racks are used to protect pumps, valves, pipelines, and other appurtenances from damage or clogging by large objects, such as tree leaves, sticks, rags, tampons, cans, plastic bags, garbage etc. Those screened larger objects are collected in the storage container and later disposed in a landfill by dump trucks. According to the method used to clean the screenings, bar racks and screens are both designated and set up as hand-cleaned or mechanically cleaned types in the WWTP. (3) Parshall flumes The Parshall Flumes, the most widely used device for measuring the flow rate of wastewater, are also installed in open channels at the influent and effluent sites of our wastewater plants. In open channel, the head, generated by an obstruction such as a special shaped flume, can be detected by the ultrasonic instrument and are used to determinate the flow rate. The correct application, selection, maintenance and calibration of flow-metering devices are critical to the efficient operation and management of a modern wastewater treatment facility. Flow meters should calibrated periodically by an authorized organization to ensure that the meter is functioning properly and accurately. (4) Vortex grit chambers Grit chambers, which are one part of pre-treatment facilities of the wastewater treatment plant, are most commonly located after the bar racks and before the primary sedimentation tanks or the equalization tanks. Sand, grit, and stones need to be removed to protect pumps, valves, pipelines, and other appurtenances of the downstream processes from damage. There are three general types of grit chambers: horizontal-flow of rectangular configuration; aerated; or vortex-type. The vortex-type consists of a cylindrical tank in which the flow enters tangentially creating a vortex-flow pattern; centrifugal and gravitational forces cause the grit to separate. The rotating turbine, installed in the center of the circular tank, controls and maintains constant flow velocity, and its adjustable pitch blades promote separation of organics from grits. The action of the rotating turbine produces a toroidal-flow path for grit particles. The grit settles by gravity into the hopper in one revolution of the basin’s contents. Solids are removed from the hopper by grit pumps or air-lift pumps. Grits removed by pumps can be discharged to a hydro clone, or called a grit washer, for removal of the remaining organic materials. Separated grits are kept in storage container for some time and periodically transported to final disposal or landfill by trucks. (5) Equalization tanks The equalization tanks are used to overcome the operation problems caused by the wastewater flow rate and strength variations, to improve the performance of the downstream processes, and to reduce the size and cost of downstream treatment facilities. The principal benefits that are cited as deriving from application of flow and strength equalization are as follows: (1) biological treatment is enhanced, because shock loadings are eliminated or can be minimized, inhibiting substances can be diluted, and pH can be stabilized, and dissolved oxygen in wastewater can be increased in advance if the mixing is by blowing air; (2) the effluent quality and thickening performance of secondary sedimentation tanks following biological treatment is improved through constant solids loading; (3) sand filtration surface-area requirements are reduced, filter performance is improved, and more uniform filter-backwash cycles are possible; and (4) in chemical treatment, damping of mass loading improves chemical feed control and process reliability. (6) Contact aeration basins The principal application of the aerobic biological treatment process is for the removal of the carbonaceous organic matter in wastewater, usually measured as biological oxygen demand, i.e. BOD. The contact aeration basin is one kind of fixed membrane-type aerobic biological treatment, microorganisms grow and attach on honey-comb type plastic media with high specific surface rate(about 100M2/M3) and decomposes organic pollutants in the wastewater, and we provides the oxygen by the air blower into the wastewater to maintain the dissolved oxygen concentration between 1.0~3.0 mg/L. Because microorganisms of the fixed membrane-type growth would not be washed out easily, so it enables to have the long time to grow. Therefore from the bacterium, all often appears the protozoon to the metazoan. The types and quantities of microorganism are quite rich. The operation management is simple and also suitable for the treatment of industrial wastewater, but it has the possibility to cause the sludge accumulation and block the media, therefore the proper and periodical backwashing is very important. (7) Chemical coagulation/flocculation basins and sedimentation tanks Coagulation has been defined as the addition of the chemical, normally called the coagulant, to a colloidal dispersion which results in particle destabilization by the reduction in forces which tend to keep particles apart. Coagulation involves the reduction of surface charges and the formation of complex hydrous oxides. The process involves forming either flocculant suspensions of compounds which entrap desired pollutants and carry them out of solution or the formation of insoluble precipitates of the pollutants themselves. Initially, the coagulation phase of treatment is practically instantaneous and the particles are usually sub-microscopic in size. These colloidal particles then agglomerate to form settleable solids by the process of flocculation. Where coagulation utilizes force of electrostatic or interionic nature, flocculation occurs by chemical bridging or physical enmeshing mechanisms. After coagulation to destabilize the particles and flocculation to generate large particles, the pollutants can subsequently be separated from the wastewater by sedimentation, because of the increase of the settling speed . From 85 to 95 percent of the total suspended solid, 20 to 40 of the COD can be removed by the chemical precipitation in our WWTPs. (8) Sand filters Filtration, in our WWTPs, is used for achieving supplemental removal of suspended solids and particulate BOD from wastewater effluent of biological and chemical treatment processes. Granular media filtration is achieved by passing the wastewater through the beds of granular media materials at a controlled flow rate. The removal process is a complex one involving several different mechanisms such as sedimentation, adsorption, interception , straining, and impaction. The major purpose of filtration is to separate the solids from fluids by interposing a medium to fluid flow through which the fluid can pass, but the solids in the fluid are retained. It has to be emphasized that the separation will depend on the pore size and the thickness of the medium as well as the mechanisms that occur during filtration. Sand filters are the beds of granular materials which are less prone to clogging due to the greater surface area where the particles can be trapped. Granular media filtration is a cyclic operation involving two phases: filtration and backwashing. The end of the filtration phase(filtration run) is reached when the suspended solids in the effluent start to increase(break through) beyond acceptable level, or when a limiting headloss occurs across the filter bed. Once either of these conditions is reached the filtration is terminated, and filter must be cleaned (backwashed) to remove the material (suspended solids) that has accumulated within the granular filter bed. The wash water containing the suspended solids that are removed from the filter is returned to the pre-treatment facilities in the WWTP and to be treated again biologically and chemically. (9)AO+MBR
AO-MBR(anoxic-oxic membrane bioreactor) is kind of biological (10) Sludge thickening and dewatering system The sludges produced by the treatment of wastewater are composed of chemical and biological mixing sludges and the scums collected from sedimentation tanks, they would be pumped out and delivered to the sludge thickeners to reduce the water content of sludge from higher level(approximately about 98~99%) to lower level (approximately about 95%). By thickening, the quantity of sludge can be reduced about 70~80%. Then, the thickened sludges enter the storage tanks temporarily before the dewatering process. After that, the addition of the high molecular polymer (Polymer+), as the conditioner, make the thickened sludge stabilized before entering the belt filters (i.e. the dewatering facilities) which also removed the water in sludge from higher level(about 95%) to lower level (less than 80%). Finally the sludge cakes produced by the belt press are transported by the screw conveyer to the sludge hoppers and then transported, by trucks, to legal sludge disposal companies to be recycled for the sidewalk bricks or concrete.
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