Umthelela wokufunwa kakhulu kwe-oxygen yamakhemikhali (i-COD) emanzini empilweni yabantu kanye nemvelo yemvelo ubalulekile. I-COD isebenza njengesibonakaliso esibalulekile sokulinganisa ukugcwala kokungcola kwemvelo ezinhlelweni zasemanzini. Amazinga aphezulu e-COD abonisa ukungcoliswa okukhulu kwemvelo, okubeka izingozi ezinkulu kokubili ezindaweni zemvelo kanye nempilo yomphakathi.

Amakhemikhali anobuthi aphilayo angena emanzini angalimaza izinto eziphilayo zasemanzini, okuhlanganisa nezinhlanzi, futhi anganqwabelana ngochungechunge lokudla, ekugcineni angene emzimbeni womuntu futhi aholele ebuthi obungapheli. Isibonelo, ukuchayeka isikhathi eside ezintweni ezifana ne-DDT kuye kwahlotshaniswa nemiphumela emibi ohlelweni lwezinzwa, ukulimala kwesibindi, ukungasebenzi kahle komzimba, kanye nokuphazamiseka okungenzeka kwezinhlelo zokuzala nezakhi zofuzo, okuhlanganisa nezingozi ezengeziwe zokukhubazeka kokuzalwa kanye nesifo somdlavuza.

Amazinga aphezulu e-COD nawo aphazamisa ikhwalithi yamanzi futhi aphazamise ibhalansi yemvelo. Lapho ukungcola kwezinto eziphilayo kungena emifuleni nasemachibini ngaphandle kokwelashwa ngesikhathi, okuningi kucwiliswa ezidakeni ezingezansi. Ngokuhamba kwesikhathi, lezi zinto eziqongelelekile zinemiphumela enobuthi yesikhathi eside empilweni yasemanzini. Lokhu kubonakala ngezindlela ezimbili eziyinhloko: okokuqala, ukufa okukhulu kwezinhlobo zasemanzini kungase kwenzeke, kuphazamise imvelo futhi kuholele ekuweni kwezindawo zokuhlala zasemanzini; okwesibili, ubuthi buqongelelana kancane kancane ezintweni eziphilayo ezifana nezinhlanzi nezinhlanzi. Ukudla kwabantu ukudla kwasolwandle okungcolile kuholela ekudlulisweni nasekuqongeleleni kwalezi zinto eziyingozi emzimbeni, okudala izingozi ezinkulu zempilo zesikhathi eside, okuhlanganisa umdlavuza, ukukhubazeka kokukhula, kanye nokuguqulwa kwezakhi zofuzo.

Ngaphezu kwalokho, amazinga aphezulu kakhulu e-COD aphazamisa amandla okuzihlanza ngokwemvelo emizimba yamanzi. Ukuwohloka kwezinto eziphilayo kudla umoya-mpilo oncibilikisiwe (DO), futhi lapho ukusetshenziswa komoya-mpilo kudlula amazinga okuvuselela umoya-mpilo, amazinga e-DO angehla afinyelele ku-zero, okuholela ezimweni ezingena-aerobic. Ngaphansi kwezimo ezinjalo, umsebenzi wamagciwane angena-aerobic uyaqhubeka, ukhiqiza igesi ye-hydrogen sulfide futhi ubangele amanzi ukuba abe mnyama futhi akhiphe iphunga elibi—izinkomba ezivamile zokungcola okukhulu.

Ukusetshenziswa kwabahlaziyi be-COD kudlala indima ebalulekile ekuqapheni nasekuvimbeleni amazinga e-COD amaningi. Isihlaziyi se-Boqu'COD sisetshenziswa kabanzi ekuhlolweni kwamanzi angaphezulu, amanzi angaphansi komhlaba, indle yasekhaya, kanye namanzi angcolile asezimbonini. Sisekela kokubili ukuhlolwa okuphuthumayo okusheshayo endaweni kanye nokuhlaziywa kwekhwalithi yamanzi okusekelwe elabhorethri okunembile, okwenza kube ithuluzi eliguquguqukayo lokuqapha imvelo kanye nokulawula ukungcola.