Domestic Wastewater Treatment Mobilization Construction - AskTOP

EM 1110-3-1721 1 May 84Table 13-1 . Typical Chlorine Dosages Required for Sewage DisinfectionType of Effluent tobe DisinfectedDosagemg/lDosagepounds/mil gallonRaw Wastewater 20 167Raw Wastewater (Septic) 50 417Settled Wastewater 20 167Settled Wastewater (Septic) 40 334Trickling Filter Effluent 15 126Activated Sludge Effluent 8 67For the recommended treatment scheme presented in chapter 5, chlorinedosages of 15 mg/l or 126 pounds/mil gallon will be applied at averagedaily flows and a maximum of 27 mg/l or 226 pounds/mil gallon will beapplied at peak daily flow rates, when disinfection is required .Sodium hypochlorite solution normally provides 12 .5 percent availablechlorine, and calcium hypochlorite solution normally provides 70percent available chlorine . To determine the equivalent dosagesrequired for these chemicals if used to disinfect the various types ofeffluents described above, divide the dosage figures by the fraction ofavailable chlorine attributable to the specific chlorine compound .Chlorination of wastewater can reduce its BOD by 15 to 35 percent ; thisis a common practice to relieve overloaded plants until additionalcapacity is provided . Approximately 2 mg/l of BOD can be removed by 1mg/l of chlorine up to the point at which residual chlorine isproduced . Odor control can be achieved by prechlorination doses of 4to 6 mg/1 . Odors off sludge drying beds can be reduced by applyingcalcium hypochlorite at a rate of 1/2 pound per 100 square feet of bedarea . Periodic application of chlorine to trickling filter influentwill reduce filter clogging and ponding . A chlorine dose of 1 to 10mg/1 based on the returned sludge flow is sometimes required forcontrol of bulking sludge in an activated sludge process . A chlorineresidual of 1 mg/l in sludge thickener supernatant prevents sludge frombecoming septic during its holding period .d . Mixing . Rapid mixing at the point of chlorine application iscritical for disinfection efficiency, while adequate mixing at the samepoint is critical for control purposes . The following methods areacceptable mixing practices to be used at Army installations : thehydraulic jump, submerged weir, the over and under baffle, themechanical mixer, and the closed conduit flowing full and with adequateturbulence .13-4 . Chlorine feeding equipment . The chlorinator capacity will bedesigned to have a capacity adequate to provide the dosage requirementstipulated in paragraph 13-3 .d . a t maximum flow conditions . Designconsiderations will be based on the assumption that chlorine can be13-2