Treatment of Dilute Manure Wastewaters by Chemical Coagulation
Results from laboratory coagulation-settling experiments using five coagulants (one inorganic salt and four organic polymers) on four dilute wastewaters (fresh manure from swine, poultry, and cattle and effluent from a swine anaerobic digester) are presented to provide chemical coagulation data for designing treatment facilities for livestock and poultry. Adjustment of pH alone was generally ineffective in promoting coagulation on all wastewaters. Values of pH above nine were effective for swine wastewater. Ferric chloride removed 60 to 70% of the volatile solids (VS) for cattle and swine at concentrations of 300 to 450 mg/L, but was less effective on poultry wastewater. Addition of organic polymers with iron salt did not improve coagulation from swine wastewater. Synthetic polymers and chitosan were excellent coagulants for all manure wastewaters but not for digester effluent. Based upon the effective concentrations to remove suspended solids from the flush waters of a 1,000-head swine finishing unit, synthetic polymers are the most cost-effective chemical coagulant, while chitosan is the least cost-effective.