Hauv nroog, nws tseem hu ua Wastewater purification plant lossis dej phwj kho cog. Thaum cov effluent muab tso rau hauv cov kav dej hauv nroog, qhov chaw kho mob yog ib hom kev kho mob pretreatment. Lub chaw kho dej khib nyiab yog ib txoj kab ke uas muaj ntau yam txheej txheem. Tus nqi thiab kev ua haujlwm ntawm txhua chav tsev txheej txheem yog sib cuam tshuam thiab cuam tshuam rau ib leeg, thiab thaum kawg txiav txim siab tus nqi thiab kev ua haujlwm ntawm tag nrho cov kab ke.
Hauv nroog, nws tseem hu ua Wastewater purification plant lossis dej phwj kho cog. Thaum cov effluent muab tso rau hauv cov kav dej hauv nroog, qhov chaw kho mob yog ib hom kev kho mob pretreatment. Lub hom phiaj dav dav ntawm kev kho cov dej khib nyiab yog tshem tawm cov khib nyiab thiab txhim kho cov pa oxygen (uas yog, kom ruaj khov cov organic teeb meem), thiab qee zaum tua kab mob thiab kho ntxiv. Kev kho cov dej khib nyiab hauv kev lag luam tsom rau kev tshem tawm lossis hloov cov roj, tshem tawm cov khib nyiab, cov hlau hnyav, thiab cov organic residue uas cuam tshuam kev ua haujlwm ntawm cov dej phwj hauv nroog, thiab kev hloov kho pH.