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5. Contaminant Removal Performance Summary for the Waterloo Biofilter® Note: Technologies were allowed a start-up period, when measures of removal performance would be excluded from the test period. We define the start-up period as ending when the technology attains effluent levels below 30 mg/1 BODS; 30 mg/1 TSS; and 19 mg/1 IN. These levels are performance thresholds for alternative systems set by MA DEP. The data from all three units from the second sampling event attained levels below 30/30/19 mg/l, so that only the first sample event was excluded under the start-up period rules. Biochemical Oxygen Demand (BOD,, removal BODS measured in the technology effluent averaged 9.3 mg/I (median, 8.0 mg/1) over the monitoring period, versus 175 mg/l for influent wastewater, representing a removal rate of 95 per cent (Table 1, Appendix 1 & 2)). Measurements exceeded the threshold 30 mg/1 level only 2% of the time (3 samples out of 124 taken). Standard deviation, reflection of the variability of the performance was relatively low; an indication that the technology was able to provide good removal performance consistently over the testing period. Table 1. Biochemical Oxygen Demand (5 -day) removal performance of the Waterloo Biofiltet® system during testing at the Massachusetts Alternative Septic System Test Center - June 1999- June 2001. BOD (mg/1) Replicate 1 Replicate 2 Replicate 3 Influent Mean %Removal Average 9.7 8.9 9.1 174.5 9.3 94.7% Median 9.0 7.5 8.0 162.0 Standard Deviation 6.0 6.7 8.1 59.8 Maximum 28.0 36.0 36.0 385.0 Minimum 1.0 1.0 1.0 83.0 Count 46 46 32 46 Count> 30 m /1 0 1 2 The three maximum values occurred in May 2000. At that time, in all three units the baskets supporting the foam cube media tilted and slumped. This movement displaced the distribution manifold, causing some of the spray of septic tank effluent to miss the media column and hit the enclosure walls and short-circuit to the discharge point. Thus with each pressure dose, a portion of the technology effluent was not fully treated by the filter media, with resultant poorer effluent quality. Waterloo Biofilter® personnel repaired the baskets and subsequent samples show an improvement in the effluent quality (Appendix 1 &2) until the period January — March 2001 when levels rose above 20 mg/1. We interpret this decline as a seasonal effect: lower influent wastewater temperature and Performance Results — WaterlooBiofilter@ Page 6 of 28