The wastewater from industries varies so addition they may be either excessively acid or alkaline and may contain high or low concentrations of colored matter. These wastes maybe heavy metals or toxic materials and possibly pathogenic bacteria. These wastes may be discharged into the sewer system provided they have no adverse effect on treatment efficiency or undesirable effects on the sewer system. It may be necessary to pretreat the wastes prior to release to the municipal system or it is necessary to a fully treatment when the wastes will be discharged directly to public waters supply.