Ruwan gurɓataccen ruwa (sharar gida) da aka fitar daga tushen gurɓataccen ruwa, saboda yawan adadin ko tattarawar gurɓataccen abu, bai cika buƙatun ƙa'idodin fitarwa ba ko kuma bai cika buƙatun ƙarfin muhalli ba, don haka rage ingancin muhallin ruwa da manufofin aiki. , dole ne a inganta shi ta hanyar wucin gadi.A cikin tsarin kula da najasa, alamomin da ake buƙatar kulawa sun haɗa da nitrogen ammonia, jimlar phosphorus, jimlar nitrogen, COD, pH, narkar da iskar oxygen, da buƙatun oxygen biochemical.