【正文】 在“十五”期間對城市排水設(shè)施投資將達(dá)1200億元，而中小城市污水處理項目將占有相當(dāng)高的比重。2　排水管網(wǎng)　　排水體制是污水處理廠設(shè)計所面臨的首要問題，它不僅涉及工程投資、環(huán)境保護(hù)、工程實施的難易程度，還直接影響污水處理廠的工藝選擇。合流制區(qū)域面積至少占建成區(qū)面積的80%以上，而且八十年代以前的建成區(qū)，建筑密集，各種地下管線擁擠，要改造為分流制，需增設(shè)一套污水管網(wǎng)系統(tǒng)，難度非常大。　　傳統(tǒng)排水觀念認(rèn)為，合流管渠被暴雨釋稀溢流，當(dāng)徑污比達(dá)到57倍時，不會對水體造成危害，事實并非如此。一般截流干管取n0=12，支管系統(tǒng)適當(dāng)高于干管的截流倍數(shù)，取n0=13。該工程措施可結(jié)合城市總體發(fā)展規(guī)劃逐步實施。 分流制管網(wǎng)與排水系統(tǒng)的連接　　對于混合制排水體制的管網(wǎng)系統(tǒng)，分流制污水干管應(yīng)在合流制截流干管的最終溢流井下游接入，嚴(yán)禁先匯流再溢流。有一些工程項目，104～104m3/d進(jìn)行估算，或不考慮現(xiàn)狀管網(wǎng)的完善程度，即做為污水處理廠的設(shè)計水量。前期工作薄弱，缺少基礎(chǔ)研究，是造成實際進(jìn)廠水量水質(zhì)偏離設(shè)計規(guī)模的主要原因。 設(shè)計水量　　污水處理廠的水量規(guī)模，應(yīng)根據(jù)城市歷年供水節(jié)水統(tǒng)計資料，以現(xiàn)狀年的用水量為基礎(chǔ)，以年增長率法預(yù)測污水處理廠收水范圍內(nèi)設(shè)計年限的需水量，并實測市區(qū)主要排污口的水量，以實測污水折減系數(shù)確定其水量規(guī)模。 設(shè)計進(jìn)水水質(zhì)　　污水處理廠的設(shè)計進(jìn)水水質(zhì)，在市區(qū)選擇幾個有代表性的排污口，定期實測其水質(zhì)水量，采用加權(quán)平均確定其現(xiàn)狀水質(zhì)濃度，以此為基礎(chǔ)，結(jié)合其它監(jiān)測資料并考慮一定余地，確定設(shè)計進(jìn)水水質(zhì)。 　　污水處理廠設(shè)計應(yīng)進(jìn)行近期及遠(yuǎn)期規(guī)模的研究，以合理確定工程分期。對中小城市污水處理廠，近期建設(shè)規(guī)模不宜過大。　?、?中小城市基礎(chǔ)資料缺乏，存在諸多不確定因素，如產(chǎn)業(yè)結(jié)構(gòu)調(diào)整、某些重點污染企業(yè)的周期性運(yùn)行等，其水質(zhì)水量較難準(zhǔn)確預(yù)測。4　處理工藝 處理工藝類型及選擇　　隨著環(huán)境及法規(guī)的壓力，城市污水處理廠普遍采用二級生物處理工藝，在生物法中，有活性污泥法和生物膜法兩大類，活性污泥法因其處理效率高，在城市污水處理廠得到廣泛應(yīng)用?！　鹘y(tǒng)活性污泥及其改進(jìn)型A/0、A2/0、AB工藝，處理單元多，操作管理復(fù)雜，尤其是污泥厭氧消化工藝，對管理水平要求較高?！　≈行〕鞘形鬯幚韽S，設(shè)計規(guī)模一般在10104m3/d以下，由于其技術(shù)力量相對較弱，采用氧化溝和SBR工藝具有明顯優(yōu)勢?！　。?）氧化溝和SBR法，通常不設(shè)初沉池和污泥消化系統(tǒng)，工藝流程簡單，適合管理水平相對較低的中小城市。 雨水沖擊負(fù)荷與污泥流失　　在排水管網(wǎng)為合流制的條件下，進(jìn)入污水處理廠的污水流量雨天是晴天的24倍，當(dāng)出現(xiàn)雨水沖擊負(fù)荷時，大量活性污泥從曝氣池轉(zhuǎn)移至二沉池，并造成污泥流失。但上述方式都不能使有機(jī)物得到有效降解。 改進(jìn)型Orabl氧化溝工藝　　Orabl氧化溝由三條橢圓形同心溝渠組成，污水由外溝依次進(jìn)入中間溝及內(nèi)溝，各溝內(nèi)的有機(jī)物濃度和溶解氧濃度均不相同，在去除有機(jī)物的同時，可實現(xiàn)除磷脫氮的目的。當(dāng)雨水沖擊負(fù)荷停止后，系統(tǒng)切換至正常運(yùn)行狀態(tài)?？赏ㄟ^雙池或多池組合運(yùn)行實現(xiàn)連續(xù)進(jìn)出水?！　BR池通常每個周期運(yùn)行46小時，當(dāng)出現(xiàn)雨水高峰流量時，SBR系統(tǒng)就從正常循環(huán)自動切換至雨水運(yùn)行模式，通過調(diào)整其循環(huán)周期，以適應(yīng)來水量的變化。5　污水回用　　我國屬世界12個貧水國家之一，人均水資源占有量僅2400m3，尤其北方地區(qū)人均水資源占有量僅200400m3，水資源的緊缺狀況在一定程度上限制了工農(nóng)業(yè)生產(chǎn)和城市的發(fā)展，許多城市不得不到幾十公里以外開辟水源，其投資在1000元/m3以上。我國的天津、大連、太原、青島、泰安等地污水回用的工程實踐，充分證明了城市污水回用的經(jīng)濟(jì)性。在中小城市污水處理廠設(shè)計中，應(yīng)研究污水回用的可能性，調(diào)查研究回用對象及水質(zhì)要求，并結(jié)合回用水水質(zhì)要求進(jìn)行污水處理工藝選擇，進(jìn)行廠區(qū)總平面布置時，應(yīng)考慮污水回用的處理用地。 oxidation ditch。 structure。s of 20 centuries in 1954 at Dutch throw in the usage for the very first its a water fluid matter good, circulate the stability and manage convenience etc. technique characteristics, already at domestic and international and extensive application in live the dirty water to is dirty to manage aqueously with the industry[1].Current application than oxidize extensively the ditch type include:The ( Pasveer) oxidizes the ditch, the ( Carrousel) oxidizes the ditch, ( Orbal) oxidizes the ditch, the type of T oxidizes the ditch( three ditch types oxidize the ditch), the type of DE oxidizes the ditch to turn to oxidize the ditch with the integral oxidize the ditch because of the difference of esse in construction with circulating, therefore each characteristics[2].This text will introduce construction, mechanism, existent problem and its latest developments that Carrousel oxidize ditches primarily.2. The Carrousel oxidizes the construction of the ditchThe Carrousel oxidize the ditch to be researched to manufacture by Dutch DHV pany development in the last the pany of DHV in foundation of the ditch in the original Carrousel to permited specially the pany EIMCO to invent again with its patent in the United States Carrousel 2000 system( see the figure ), realizes the living creature of the higher request takes off the nitrogen with divided by the function of .There has been in the world up to now more than 850 Carrousels oxidize the ditch with the Carrousel 2000 system are circulating[3].From diagram therefore, the Carrousel oxidizes the ditch the usage the spirit of that definite direction control with shake up the device, face to mix with the liquid deliver the level speed, from but make drive the liquid of admixture that shake up is in oxidize ditch shut match outlet circulate oxidize the ditch have the special hydraulics flows the , current plete mix with the characteristics of the type reactor, have the characteristics that push the flow type reactor again, the ditch inside exsits obviously of deliquescence oxygen density steps the ditch cross section is rectangle or trapezoids, the flat surface shape is many for oval, the ditch internal water is deep general for ～ ｍ , the breadth is deep pare for 2:1, also have the deep water amount to 7 ms of, ditch inside average speed in water current is ms/ ditch spirit admixture equipments contain surface spirit machine, the spirit of turn to brush or turn the dish and shoot to flow the spirit machine, pipe type spirit machine with promote take care of type spirit machine etc., match with in recent years usage still contain underwater push machine[4~6].3. The Carrousel oxidizes the mechanism of the ditch The Carrousel oxidizes the ditch handles dirty and aqueous principleThe at the beginning mon Carrousel oxidizes the dirty water in inside in craft of the ditch direct with dirty mire in reflux together enter oxidize the ditch surface spirit machine makes fuse in the liquid of admixture the density of the oxygen DO increases about 2 the 3 mgs/ this kind of well the term of the oxygen , the microorganism gets the enough deliquescence oxygen es and go to divided by the BOD。Not the dirty mire in germ in form in silk inflation takes place primarily at the waste water water temperature is lower but the dirty mire carries higher microbial burthen is high, the germs absorbed the large quantity nourishment material, is low because of the temperature, metabolism the speed is slower, accumulating the rises large quantity is high to glue sexual and many sugar materials, making the surface of the live and dirty mire adhere to the water to increase consumedly, SVI the value is very high, being the dirty mire inflation.Cause that aim at the dirty mire inflation, can adopt the different counterplan:From the anoxia, water temperature high result in of, can enlargement tolerance or lower into the water measures to alleviate burthen, or the adequacy lowers the MLSS( control dirty mire reflux measure), making need the oxygen measures decrease。Can pass the hurl add the nitrogen fertilizer, phosphorus fatty, adjust the admixture nourishment in the liquid material equilibrium( BOD5:N:P=100:5:1)。Bleach the powder with the liquid chlorin( press to fuck % of the dirty m