AWWA REUSE52128

The State of California Department of Health Services (DHS) has developed draft regulations addressing groundwater recharge with reclaimed water. In recognition of the need to remove, or reduce the concentrations of health-significant organic constituents that may be present in municipal wastewater, DHS has selected total organic carbon (TOC) as a parameter to be monitored in the reclaimed water. The intent of the TOC requirement is to limit the TOC of wastewater origin in the extracted water to a maximum of 1 mg/L. Dilution, either at the point of recharge or in the aquifer, is also required to limit the maximum reclaimed water contribution to 50% unless methodology is identified and demonstrated to be as effective as a 1:1 dilution. Two questions central to the dilution requirement issue are explored in this paper. Can reclaimed water having less than or equal to 1 mg/L TOC be reliably produced? Does meeting a TOC limit of less than or equal to 1 mg/L in the reclaimed water at the point of recharge provide a level of health protection equivalent to meeting a TOC limit of less than or equal to 2 mg/L in the reclaimed water and blending it 1:1 with water of non-wastewater origin? The purpose of this paper is not to advocate elimination of the dilution requirement in the draft groundwater recharge regulations for reclaimed water used for indirect potable reuse. The intent is to suggest addition of an alternative method of treatment that could be included in the regulations to produce reclaimed water that, from a health standpoint, is at least equivalent to blended water having the same TOC concentration of wastewater origin. Includes 43 references, tables.