Ko ngā whakarewa para (pērā i te PR, NMP, PMA, me ētahi atu) i hangaia e ngā peita, waituhi, tae kakahu, me ngā hinu kakahu, ka hangaia mā ngā taputapu whakatikatika i raro i ētahi tikanga tukatuka hei whiwhi hua whakarewa. Ko te nuinga o ēnei hua ka whakamahia hei whakarewa mō ngā waituhi, peita, waituhi, tae kakahu, me ngā hinu kakahu, tae atu ki ngā kaihoko horoi i roto i te hanga whakaaturanga karaihe wai.
Mā te whakauru i te hangarau me ngā taputapu a te Kamupene Ogano, he kamupene Hapanihi kua rārangihia, neke atu i te 70 tau o te wheako ki te maimoatanga wai, mā te whakamahi i te whakakore waikawa-pūtake, te whakatō matū, te whakahāngaitanga Fenton, te whakapūngao hau pēhanga, te whakahāngaitanga anaerobic, me te tohanga ā-roto IC anaerobic. Ko te tauhohenga hāora anaerobic, te whakahāngaitanga whakapā, te mimiti waro whakahohe me ētahi atu tukanga maimoatanga wai para ka taea e te kamupene te tino rite ki ngā taputapu, hangarau me ngā pūkenga ki te hangarua me te maimoatanga i ngā wai para waro kukū-teitei, ngā wai para kei roto te wheori, ngā waikawa para me ngā para kawakore, ngā wai para kei roto te parahi me ētahi atu wai para ahumahi me ngā wai para kāinga. Ko te kaha tukatuka o ia rā o ngā wai para ka eke ki te neke atu i te 100 tana. Ka taea te whakamahi anō i te wai kua rongoatia hei wai horoi i roto i te awheawhe whakaputa me te whakakaiao i te rohe wheketere, kia tutuki ai te whai huatanga o ngā rauemi.