一、概述
水(shui)資源是經濟發(fa)展和社會可持(chi)續發(fa)展的(de)一個重要(yao)因素，城(cheng)市污(wu)(wu)水(shui)處理(li)率(lv)已成(cheng)為(wei)一個地區(qu)文明與否的(de)一個重要(yao)標志(zhi)。污(wu)(wu)水(shui)處理(li)已從原始(shi)的(de)自然處理(li)、簡單的(de)一級處理(li)發(fa)展到利用(yong)各種先(xian)進技術、深度處理(li)污(wu)(wu)水(shui)，并(bing)回(hui)用(yong)。處理(li)工(gong)藝也從傳(chuan)統活性污(wu)(wu)泥法、氧化溝(gou)工(gong)藝發(fa)展到現在(zai)多種工(gong)藝，以達到不同的(de)出水(shui)要(yao)求。
二、污水處理流程
一般(ban)的(de)污水(shui)(shui)處(chu)(chu)理(li)(li)(li)(li)主要采(cai)用(yong)(yong)二級處(chu)(chu)理(li)(li)(li)(li)方(fang)式：第一級為(wei)機械(xie)(xie)處(chu)(chu)理(li)(li)(li)(li)，一般(ban)采(cai)用(yong)(yong)格柵等機械(xie)(xie)設備過濾(lv)污水(shui)(shui)中(zhong)漂浮物(wu)或顆(ke)粒較大的(de)物(wu)質；第二級為(wei)生化處(chu)(chu)理(li)(li)(li)(li)，根據不同(tong)處(chu)(chu)理(li)(li)(li)(li)要求，處(chu)(chu)理(li)(li)(li)(li)污水(shui)(shui)中(zhong)含有(you)的(de)各種超(chao)標的(de)硅物(wu)質或金屬元(yuan)素(su)，使處(chu)(chu)理(li)(li)(li)(li)后的(de)水(shui)(shui)能滿足(zu)后續(xu)用(yong)(yong)水(shui)(shui)設備的(de)要求，如生活用(yong)(yong)純凈水(shui)(shui)、工業鍋爐軟化與(yu)除鹽(yan)水(shui)(shui)等。
三、現場工況
污水(shui)集水(shui)池中(zhong)的(de)污水(shui)經兩臺污水(shui)泵(beng)1#污水(shui)泵(beng)2#將水(shui)送入沉淀池，為防止(zhi)沉淀池水(shui)溢出發生(sheng)事故，沉淀池中(zhong)設置有水(shui)位(wei)檢(jian)測(ce)裝置，當實際水(shui)位(wei)超過報警水(shui)位(wei)時(shi)控(kong)制系統自(zi)動關閉(bi)格柵前的(de)電動蝶閥以防止(zhi)發生(sheng)溢水(shui)事故。沉淀池中(zhong)的(de)污水(shui)再(zai)由生(sheng)化(hua)(hua)水(shui)泵(beng)送入生(sheng)化(hua)(hua)處(chu)理池，生(sheng)化(hua)(hua)處(chu)理池也設有水(shui)位(wei)上限檢(jian)測(ce)，通過控(kong)制生(sheng)化(hua)(hua)水(shui)泵(beng)控(kong)制生(sheng)化(hua)(hua)處(chu)理池水(shui)位(wei)。
四、改造方案
1、沉淀池兩臺水泵由一臺變頻器采用一拖二控制；
2、采(cai)用可靠(kao)性較高的(de)PLC+變頻(pin)器的(de)方式(shi)；
沉淀(dian)池內設(she)置有上(shang)限(xian)(xian)(xian)、下(xia)限(xian)(xian)(xian)水(shui)(shui)(shui)(shui)位(wei)(wei)(wei)及上(shang)、下(xia)限(xian)(xian)(xian)報(bao)警水(shui)(shui)(shui)(shui)位(wei)(wei)(wei)檢(jian)測。其控制過程為(wei)當(dang)(dang)水(shui)(shui)(shui)(shui)位(wei)(wei)(wei)達到(dao)(dao)下(xia)限(xian)(xian)(xian)時(shi)，水(shui)(shui)(shui)(shui)位(wei)(wei)(wei)檢(jian)測將信號(hao)(hao)送給(gei)PLC，PLC啟(qi)動變(bian)(bian)頻器(qi)并將頻率上(shang)升信號(hao)(hao)輸出給(gei)變(bian)(bian)頻器(qi)，當(dang)(dang)變(bian)(bian)頻器(qi)頻率達到(dao)(dao)50Hz時(shi)若此時(shi)水(shui)(shui)(shui)(shui)位(wei)(wei)(wei)仍處于下(xia)限(xian)(xian)(xian)位(wei)(wei)(wei)置，PLC發出切換(huan)信號(hao)(hao)將污水(shui)(shui)(shui)(shui)泵(beng)1#切換(huan)到(dao)(dao)工頻運行，延時(shi)一段時(shi)間后由變(bian)(bian)頻器(qi)啟(qi)動污水(shui)(shui)(shui)(shui)泵(beng)2#。相反(fan)，當(dang)(dang)水(shui)(shui)(shui)(shui)位(wei)(wei)(wei)達到(dao)(dao)上(shang)限(xian)(xian)(xian)位(wei)(wei)(wei)置時(shi)則停止(zhi)污水(shui)(shui)(shui)(shui)泵(beng)1，PLC發出變(bian)(bian)頻器(qi)頻率下(xia)降信號(hao)(hao)，若因水(shui)(shui)(shui)(shui)泵(beng)或(huo)其它原(yuan)因造成水(shui)(shui)(shui)(shui)位(wei)(wei)(wei)低于下(xia)限(xian)(xian)(xian)或(huo)上(shang)限(xian)(xian)(xian)水(shui)(shui)(shui)(shui)位(wei)(wei)(wei)報(bao)警時(shi)，水(shui)(shui)(shui)(shui)位(wei)(wei)(wei)檢(jian)測器(qi)將報(bao)警信號(hao)(hao)送給(gei)PLC，由PLC輸出啟(qi)動報(bao)警電路（報(bao)警指燈與響鈴(ling)），以提示操作人員查看原(yuan)因。
曝氣機(ji)(ji)和潛水(shui)泵是(shi)污水(shui)處理的核心設(she)備，需要用(yong)變頻器對曝氣機(ji)(ji)的鼓風(feng)機(ji)(ji)（羅茨風(feng)機(ji)(ji)）和潛水(shui)泵速， 鼓風(feng)機(ji)(ji)變頻控制：污水(shui)處理好氧部分(fen)溶(rong)(rong)(rong)解氧濃(nong)度(du)對處理結果(guo)有很大影(ying)響，溶(rong)(rong)(rong)解氧濃(nong)度(du)太(tai)低，污水(shui)不能達標(biao)；溶(rong)(rong)(rong)解濃(nong)度(du)太(tai)高，不僅浪費電能還(huan)可能使活性污泥上浮使出水(shui)也不能達標(biao)，鼓風(feng)機(ji)(ji)加變頻器就是(shi)為了控制CASS池溶(rong)(rong)(rong)解氧的濃(nong)度(du)穩定在恒定值。
五、結論
污水(shui)處理廠經過變頻(pin)改(gai)造后不僅提高了自動(dong)化程度和(he)控(kong)制精度，同(tong)時在節(jie)能降耗上也大大獲益(yi)，綜合節(jie)電率達35%，企(qi)業效益(yi)和(he)社會效益(yi)同(tong)步(bu)大幅提升。
