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STIG PROJECT -- EVALUATION OF WATER FOR INJECTION -- 28 March 1994 2 Il. LIQUID COMPOSITIONS A partial flow diagram for the system is shown in Figure 1 which is based on the UIC Permit Application'. Source liquid is processed effluent from the City of Lodi White Slough Water Pollution Control Facility(WSWPCF).Water drawn from WSWPCF passes through a filter sequence in the plant, prior to other use. Filtering removes some components that might otherwise be troublesome. Subsequent processing and uses in the plant increase concentrations of most dissolved components in liquid sub-streams. Four sub-streams are combined for injection/disposal, which is the main focus of this review.The several fluid compositions which develop in the plant involve many technical aspects, including their potential to form mineral scales. Such in-plant factors are recognized here mainly in terms of their plausible consequences for injectability of the resulting mixture. A. Water Compositions Composition of the source was defined by sampling and chemical analysis over a period of about nine months in 1992-1993. Twenty-six sets of chemical data were available for this review. The first fifteen were obtained during a 26-day interval in October-November 1992. The remainder were obtained at modestly irregular intervals during the succeeding 230 days. Plots of these data are shown in Figures 2A and 2B. No persistent time-trends appear in the data sett. Individual component concentrations are generally more variable than ±10 percent of the central values. Irregular shifts in concentration occur for some components, especially silica. Shifts for various components are unsynchronized or weakly synchronized.Average numerical compositions based on these data are used as a basis for modelling. Values are shown in Table 1 where they take several forms. Column 1: overall average of measured values derived by; • weighting the average of the first 15 samples as a single composition • combining that with the unweighted values of the other eleven compositions so that average values are based on twelve sets of data spaced fairly regularly through time Column 2: median values for the 26-member group Column 3: column 1 values plus twice the standard deviations Column 4: design composition used for calculating effects of treatments, particularly reverse osmosis and evapo-concentration processes. Columns 5-6:Nominal and high compositions of mixed waters representing in jectate under different assumptions. B. Waste Water Streams The water stream taken from WSWCPF passes through several processes in the plant to yield wastes of different composition. Three major and one minor waste stream are recombined for disposal.One objective of this review aims to define the range of concentrations in the mixture of recombined waste streams, specifically regarding suitability of the mixture for disposal in the injection well. Rates and concentration factors appear in the lower legend of Figure 1. DON MICHELS ASSOCIATES -Missoula,Montana USA