Nitrogen andPhosphorus Removal fromCombined Sewage Components byMicrobial Activity

FINSTEIN, M.S.(Rutgers, TheState University, New Brunswick, N.J.). Nitrogen andphosphorus removal fromcombined sewage componentsby microbial ac- tivity. Appl. Microbiol. 14:679-684. 1966.-When primary domestic sewage sludge was combined withsettled sewageorsecondary-treatment plant effluent, synergism resulted. Theactivity (measured byoxygen uptake, andtheremovalofKjeldahl nitrogen andorthophosphate fromsolution) whichresulted fromincubating sludge together withsettled sewageexceeded thesum oftheactivities whenthese compo- nents wereincubated separately. A similar synergistic effect occurred withsludge andeffluent. Thesewagesludges weredeficient inreadily available nitrogen, butno shortage ofphosphorus was demonstrated. Theaddition ofammoniumandortho- phosphate salts tosludge, inconcentrations equivalent tothosefoundinsettled sewageandeffluent, stimulated sludge oxygen uptake atleast 80% as much as settled sewageor effluent. Itissuggested thatthesynergism reflects increased microbial activity resulting fromwidened carbon-nitrogen andcarbon-phosphorus ratios achieved bycombining sludge withnutrient-rich settled sewage or effluent. Theundesirable growth ofalgae inreceiving waters hasdirected attention totheimportance ofremoving plant nutrient elements, aswell as carbonaceous pollutants, fromwastewaters (14). Biological treatment ofdomestic sewagedoes noteffectively removenitrogen andphosphorus, theelements ofgreatest concern.Thisdifficulty hasitsorigin inthenutrient imbalance ofsewage withrespect totherequirements ofheterotrophic bacteria forrespiration andcellsynthesis. The imbalance consists ofan excessofnitrogen and phosphorus relative tocarbon. Theportion of thenitrogen andphosphorus thatisrequired formicrobial synthesis isretained as activated sludge or trickling filter slime, whereasexcess nutrient isdischarged inthefinal effluent. Primary sedimentation may havetheeffect of aggravating thenutrient imbalanceby with- holding fromaerobic treatment thesewage frac- tionrichest incarbonaceous constituents (Table 1).Since anydecrease intheamountofmicro- biologically available carboninthefeed, rela- tive tonitrogen andphosphorus, wouldbedetri- mental tonutrient removal, primary sedimenta-