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Orenco Systems Inc. March 2002 AdvanTex AX 10 Test Report probing revealed that the grey biofilm (in the areas of the filter more distant from the distribution caps) extended only a few inches below the top of the filter. In contrast, the black coloured biofilm in the vicinity of the distribution caps extended a greater depth below the top of the filter. To improve the liquid distribution across the top of the filter, on April 25, 2001 (Day 192 in Week 28) the original (35 cap) manifold was replaced with one having a modified "diamond-shaped" (33 cap) distribution pattern, as illustrated in Photograph #2. The original filter media below the distribution cap manifold was left in place without any alteration. The biological build-up on the media was left undisturbed in order to determine whether the modifications to the distribution pattern would allow the filter to recover from ` the excessive loading and biofilm condition. 2.5.3 Increasing the Recirculation Ratio & Media Wetting Frequency L During the first 232 days of the test, the flow from the recirculation tank to the filter was set at one minute of dosing every twenty minutes, achieving a recirculation ratio of 2.0. It was ✓r noted that the majority of the drainage through the filter media was completed within one minute of the cessation of dosing, suggesting that the dosing frequency could be increased Lto improve treatment performance. On Day 233 in week 34 (June 4), the recirculation flow was changed to 20 seconds every four minutes. This increased the recirculation ratio to 3.2, and increased the frequency of ` wetting of the filter media by about five times. Although the process, at this point, had recovered; the purpose of altering the timer setting was to see if further improvement could be gained. 2.5.4 Summary �- From mid March through the end of April steps were taken to isolate potential causes for the drop in performance that occurred during the fifth month of testing. Flow to the plant was kept at 500 gpd throughout this period. The underd rain repair was made first since it L was physically inhibiting (blocking)discharge from the unit as well as the natural ventilation through the pod. Effluent quality was monitored closely for about four weeks following the underdrain repair and little apparent recovery was observed. Next, the manifold modification was made. Within a couple of weeks the unit had recovered and by the time the recirculation ratio was increased, the unit was producing an effluent with a CBODS concentration of under 20 mg/L. 2.6 Flow Reduction Prior to repeating the four stress tests in early September, the flow rate was reduced on August 4, 2001 (at the end of the 42"d week of testing) from 500 to 400 gpd. This was done to monitor the performance of the unit at a lower hydraulic loading rate. Nova Tec Consultants Inc. Page 14 of 38