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The State of California's WastewaterReclamationCriteria is under review and will be revised and expanded to include several new regulations on the use of reclaimed municipal wastewater. To provide a scientific basis for the evaluation of the existing and proposed Criteria, enteric virus monitoring data from secondary and tertiary effluents were evaluated. These virus data were obtained from special studies and monitoring reports, covering the period from 1975 to 1989, including ten municipal wastewater treatment facilities in California. Based on the enteric virus data from these reports, and using the current Criteria as a guide, four exposure scenarios were developed to determine the risk of waterborne enteric virus infection to humans as a consequence of wastewater reclamation and reuse. The exposure assessments included food crop irrigation, landscape irrigation for golf courses, recreational impoundments, and ground water recharge. The virus enumeration and the resulting risk assessments described in this paper provide a comparative basis for addressing the treatment and fate of enteric viruses in wastewater reclamation and reuse. The analyses show that annual risk of infection from exposure to chlorinated tertiary effluent containing 1 viral unit/100 L in recreational activities such as swimming or golfing is in the range of 10−2 to 10−7, while exposures resulting from food-crop irrigation or groundwater recharge with reclaimed municipal wastewater is in the range of 10−6 to 10−11. The risk analyses are also used to demonstrate that the probability of infection can be further mitigated by controlling exposure to reclaimed wastewater in the use area.

Adhesion of selected bacteria to cellulose actetate (CA) reverse osmosis (RO) membranes used in wastewater reclamation processes was investigated to determine its role in membrane fouling and reduced process efficiency. Adhesion of a hfycohcterium sp. previously isolated from an early stage of RO membrane biofouling was relatively unaffected by large variations in the ionic strength or pH of the buffer system. However, trace quantities of a polyoxyethylene ether nonionic detergent almost completely inhibited attachment. The mycobacteria were found to adhere to the CA membrane surface (or to a CA-affinity column) approximately 2.5fold more effectively than a wild-type strain of Escherichia coli The ability of Mycobucterium and E. coli to adhere to the membrane was correlated with their relative surface hydrophobicities as determined by their affinities for n-hexadecane. A similar correlation was established between a hydrophilic wild-type strain of Acinetobactev phos&devorus containing a single 17.8 mega-Dalton plasmid (PYGl) and a more hydrophobic isogenic derivative strain (P7P-) lacking the PYGl plasmid. Unlike the P7WT parent strain, the P7P-derivative produced more fimbrialike appendages, which may account for its enhanced hydrophobic and adhesive properties. The results suggest that hydrophobic interactions between bacterial cell surface components and the CA membrane surface play an important role in the initial stages of bacterial adhesion and RO membrane biofilm formation. JULY 1985 H.F. RIDGWAY ET AL 99

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The kinetics of adhesion of a Mycobacterium sp. to cellulose diacetate reverse-osmosis membranes is described. This Mycobacterium sp. (strain BT2-4) was previously implicated in the initial stages of reverseosmosis membrane biofouling at a wastewater reclamation facility. Adhesion of BT2-4 cells to the cellulose diacetate membrane surfaces occurred within 1 to 2 h at 30°C and exhibited saturation-type kinetics which conformed closely to the Langmuir adsorption isotherm (Pearson r correlation coefficient = 0.977), a mathematical expression describing the partitioning of substances between a solution and solid-liquid interface. This suggests that the cellulose diacetate membrane surfaces may possess a finite number of available binding sites to which the mycobacteria can adhere. Treatment of the attached mycobacteria with different enzymes suggested that cell surface polypeptides, a-1, 4or a-1,6-linked glucan polymers, and carboxyl ester bond-containing substances (possibly peptidoglycolipids) may be involved in mycobacterial adhesion. The possible implications of these findings for reverse-osmosis membrane biofouling are discussed.