Proceedings of the International Symposium on Efficient Water Use in Urban Areas


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Trace Organics Removal. The regulations intend to control the concentration of organics of municipal wastewater origin as well as anthropogenic chemicals that have an impact on health when present in trace amounts. Thus, the dilution requirements and the organics removal specified in Project Categories I and IV in Table 4 are to limit average concentration of unregulated organics in extracted groundwater affected by the groundwater recharge operation. The concentration of unregulated and unidentified trace organics is of great concern since other constituents and specific organics are dealt with through the established maximum contaminant levels and action levels developed by the California Department of Health Services (CDHS).

Approximately 90 percent by weight of the organics comprising the total organic carbon (TOC) in treated municipal wastewater are unidentified (State of California, 1987). One of the health concerns related to the unidentified organics is that an unknown but small fraction of them are mutagenic. Regulation of the presence of trace amount of organics in reclaimed water can be accomplished by dilution using surface water or groundwater of less contaminated source. When reclaimed water makes up more than 20 percent of the water reaching any extraction well for potable water supply, treatment to remove organics must be provided. Because of lack of an ideal measure for trace amount of organics in reclaimed water as well as in the affected groundwater, total organic carbon (TOC) was chosen, as a surrogate, to represent the unregulated organics of concern. Although TOC is not a measure of specific organic compounds, it is considered at present to be a suitable measure of gross organics content of reclaimed water as well as groundwater for the purpose of determining organics removal efficiency in practice. However, there is insufficient basis for the establishment of a gross organics standard for the recharge water that protects public health.

Table 4. Estimated log virus removal by wastewater treatment in different project category¹

Project category²	Treatment requirements	Log virus removal³

I	Primary/secondary/filtration/ Organics removal/disinfection	7
II	Primary/secondary/filtration/ Disinfection	6
III	Primary/secondary/disinfection	3
IV	Primary/secondary/filtration/ Organics removal/disinfection	6

¹Adapted from State of California, 1992 and Hultquist, et al., 1991. ²Refer to Table 3 for the Project category. ³Log removal is the negative log of the fraction remaining. Thus, the fraction remaining is 0.10, it is equivalent to one log removal. Conversely, 99.999% removal or 0.00001 remaining is the equivalent of 5 logs removal.

Inorganic Chemicals. Inorganic chemicals, with the exception of nitrogen in its various forms, are adequately under control if all maximum contaminant limits (MCLs) regulated by CDHS are met. By limiting the concentration of total nitrogen in the reclaimed water, detrimental health effects such as methemoglobinemia can be prevented. In those recharge operations where adequate nitrogen removal cannot be achieved by treatment processes or passage through an unsaturated zone, the criteria provide the alternative method such as well head treatment to reduce the total nitrogen concentration to below the allowable concentration of 10 mg/L as N.

Table 5. Estimate of overall removal of enteric viruses in groundwater recharge systems due to the combined effects of treatment processes, soil systems, and retention in groundwater^{1 2}

Project category	Treatment requirements	Log virus removal³

I	Primary/secondary/filtration/ Organics removal/disinfection	17
II	Primary/secondary/filtration/ Disinfection	16
III	Primary/secondary/disinfection	14
IV	Primary/secondary/filtration/ organics removal/disinfection	13

¹Adapted from State of California, 1992 and Hultquist, et al., 1991. ²Infiltration rate of 7.3 m/day was assumed for virus removal with soils in unsaturated zone.

SUMMARY AND CONCLUSIONS

To increase the natural supply of groundwater, artificial recharge of groundwater basins is becoming increasingly important in groundwater management and particularly in situations where the conjunctive use of surface water and groundwater resources is considered.

Several constraints limit expanding use of reclaimed municipal wastewater for groundwater recharge. The lack of specific criteria and guidelines governing the artificial recharge of groundwater with reclaimed municipal wastewater is currently hampering the implementation of large-scale groundwater recharge operations; thus, the establishment of policy and regulations for the planning and implementing new groundwater recharge projects has been proposed. The rational basis and other background information for the proposed groundwater recharge regulations are presented in this paper. These regulations will serve as a basis with which future groundwater recharge projects are evaluated. Two case histories are presented for the soil aquifer treatment and non-potable water reuse with less stringent water quality requirements.

ACKNOWLEDGEMENTS

Information contained in this paper was updated and revised with case histories. However, portions of the material in this paper were previously presented at various places which included the NATO Advanced Study Institute, Acquafredda di Maratea, Italy, May 24-June 5, 1992, and Water Down Under 94, Adelaide, South Australia, Australia, November 21-25, 1994.

REFERENCES

Asano, T., Wassermann, K.L. (1980). “Groundwater recharge operations in California,” Journal American Water Works Assoc. 72, 7, 380-385

Asano, T. (ed.) (1985). Artificial Recharge of Groundwater, Butterworth Publishers, Boston, MA.

Bennani, A.C., Lary, J., Nrhira, A., Razouki, L., Bize, J., and Nivault, N. (1992). “Wastewater treatment of greater Agadir (Morocco): an original solution for protecting the bay of Agadir by using the dune sands,” In:Waste water management in coastal areas, March 31-April 2, 1992, Montpellier, CFRP-AGHTM, Paris, France.

Bouwer, H. (1978). Groundwater Hydrology, McGraw-Hill Book Co, New York, New York.

Bouwer, H. (1988). “Groundwater recharge as a treatment of sewage effluent for unrestricted irrigation,” In: Pescod, M.B. and Arar., A. (eds.). Treatment and Use of Sewage Effluent for Irrigation, Butterworth Publishers, Boston, MA.

Brissaud, F., Salgot, M., Bancole. A., Campos, C., and Folch, M. (1998). “Residence time distribution and disinfection of secondary effluents by infiltration and percolation.” Advanced Wastewater Treatment, Recycling and Reuse Proceedings, Volume 1, pp. 371-378, Fiera Milano, 14-16 September 1998, Milan, Italy.

Hultquist, R.H., Sakaji, R.H., Asano, T. (1991). “Proposed California regulations for groundwater recharge with reclaimed municipal wastewater”. American Society of Civil Engineers, Environmental Engineering Proceedings, 759-764, 1991 Specialty Conference/EE Div/ASCE, New York, New York.

National Research Council (1982). Quality Criteria for Water Reuse, Panel on quality criteria for water reuse, National Academy Press, Washington, D.C.

National Research Council (1994). Groundwater Recharge Using Waters of Impaired Quality,” National Academy Press. Washington, D.C.

Roberts, P.V. (1980). “Water reuse for groundwater recharge: an overview,” Journal American Water Works Assoc., 72, 7, 375.

State of California (1978). Wastewater reclamation criteria, code of regulations, Title 22, Division 4, Environmental Health, Department of Health Services, Sacramento, C.A.

State of California (1987). Report of the scientific advisory panel on groundwater recharge with reclaimed wastewater, Prepared for State Water Resources Control Board, Dept. of Water Resources, and Dept. of Health Services, Sacramento CA.

State of California (1992). Proposed guidelines for groundwater recharge with reclaimed municipal wastewater, and Background information on proposed guidelines for groundwater recharge with reclaimed municipal wastewater, Interagency water reclamation coordinating committee and the Groundwater recharge committee, Sacramento, CA.

Todd, D.K. (1980). Groundwater Hydrology, 2nd ed. John Wiley and Sons, New York, New York.

World Health Organization (1989). Health guidelines for the uses of wastewater in agriculture and aquaculture, Report of a WHO Scientific Group, Technical Report Series 778, World Health Organization, Geneva, Switzerland.

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