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The effectiveness of various filtration agents in the primary treatment of dairy processing wastewater was investigated in laboratory-scale studies. The filtration agents used were: zeolite, crushed coral, charcoal, sand and crushed coral and sand and glass beads. The effectiveness of the filtration media was determined by testing parameters such as chemical oxygen demand (COD), total solids (TS) and total suspended solids (TSS) before and after filtration of wastewater. Percent reduction of the different parameters as a result of filtration was calculated. Sand combined with crushed coral or glass beads was found to be the most effective filtering medium with an average reduction of 99% in TSS, 93% in COD and 51% in TS. Charcoal filtration resulted in an average 85% reduction in TSS, 83% reduction in COD and 46% reduction in TS. Filtration using crushed coral resulted in an average 83% reduction in TSS, 78% reduction in COD and 39% reduction in TS. Zeolite was the least effective of the four media; it resulted in an average reduction of 78% in TSS, 76% in COD and 30% in TS. The differences among mean values of COD, TSS and TS after the different treatments were analyzed statistically using analysis of variance (ANOVA). When differences among means were found to be statistically significant (p < 0.0001), each mean value was compared with every other mean value using Duncan's multiple range test and least significant difference (LSD) test. Comparison of the mean values indicated the following: No significant difference between means of zeolite and crushed coral treatment. Mean values of COD, TSS, and TS of charcoal treatment were significantly different from the other treatments. Sand combined with crushed coral or glass beads was the most effective filtration agent and the means were significantly different from the means of the other treatments.

Research was conducted to assess the practical use of an ATP bioluminescence assay to evaluate the bacteriological quality of raw milk. Filtration was used to precondition samples before ATP determination, which was measured in relative light units (RLUs). The Lumac ATP bioluminescence assay results were compared with standard plate counts (SPCs) of samples to estimate the microbial load for 246 raw milk samples that were split and either tested immediately or subjected to two preliminary incubation temperatures, 12.8 and 15.6 degrees C, for 18 h. Linear regression analysis procedures were used to analyze the data. Preincubation treatments were analyzed separately. For all treatments, linear regression coefficients were significantly different from zero (P < 0.01). The R2 values calculated using log10-transformed SPC and log10-transformed RLUs for samples tested immediately and samples preliminarily incubated at 12.8 and 15.6 degrees C were 0.58, 0.78, and 0.80, respectively. The R2 for all samples combined was 0.78. Differences in regressions among treatments were tested using a multiple slope and intercept model. Treatment intercepts and slopes were significantly different (P < 0.01). A linear regression equation was used to predict SPC from ATP values. Comparison of predicted values with actual SPCs indicated that ATP could be useful in predicting SPC in raw milk.

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