Pulp and paper making is a highly water-intensive process,estimated to use as much as 60 m~3(15,850 gallons)of water per ton of paper produced.1 With that usage comes high volumes of wastewater that not only must be treated but must also meet increasingly more stringent water quality regulations.To meet these more stringent requirements necessitates new technology and potential redesign of existing wastewater treatment plants(WWTPs).To address those requirements,this paper will provide an overview of different chemical addition/removal strategies,physical tertiary treatments,and biological technologies used to reduce or remove phosphorus from WWTP effluent.Examples of each technology will also be presented.Although some municipalities have been required to meet a monthly phosphorus average of less than 1 mg/L since the early 1990s,the carryover is that industrial users are required to meet the same standards for their wastewater permits.Permits from the National Pollutant Discharge Elimination System(NPDES)regulate the total maximum daily load(TMDL),as well as monthly maximums of phosphorus allowed into U.S.receiving waters: these monthly maximums are also trending lower.It is important to note that phosphorus in wastewater is generally reported as orthophosphate or P2O5.Typical pulp-and-paper WWTPs already remove 80%-90% of the phosphorus in their wastewater,but the trend is toward achieving a standard of less than lmg/L phosphorus in effluent.Many plants already have to meet these stringent requirements due to the nature of the receiving waters to which they discharge.
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