Coagulation of alkalinized municipal wastewater using seawater bittern

Laboratory studies were conducted to determine the efficacy of seawater bit tern as a coagulant for the treatment of municipal wastewater. Freshly coll ected grab samples of municipal wastewater from two different discharge poi nts were alkalinized to pH levels of 11.4 +/- 0.1 by adding staked lime or caustic soda. Serial dosages of liquid bittern were added and the jar test technique was used to determine the effect of the process on a number of de terminant parameters. Seawater, liquid bittern, and dried bittern were used as coagulating agents in one of the four test sets to determine the effect of the three magnesium ion (Mg2+) sources on effluent characteristics. The extent of bacterial inactivation and the use of CO2 to control effluent pH were investigated as well. Seawater liquid bittern was found to be an effe ctive and economic source of Mg2+ that may be used in the treatment of muni cipal wastewater. Turbidity and suspended solids removal exceeded 95%. Reco rded chemical oxygen demand removals were in excess of 75%, while dissolved organic carbon removals averaged approximately 30%. Very limited differenc es in efficiency of treatment were noted between the use of slaked lime and caustic soda as alkalinizing agents. Besides its reduced bulk when compare d to seawater, liquid bittern demonstrated an added advantage (over seawate r and dry bittern) in imparting the least increase in dissolved solids to t reated effluent. The process is very effective in inactivating fecal bacter ia. Carbonation by the addition of CO2 in concentrations ranging between 56 and 362 mL/L (depending on initial levels of pH, alkalinity, and the natur e of the alkalinizing agent used) were needed to neutralize clarified super natants to acceptable levels.