Thanks very much Don. You have given me some good information there. There was no form of pH control at this plant. The last 2 weeks I have been manually dosing hydrated lime for mainly alkalinity but also for pH , as well as NaOH. The SBR is set up like this : sewer enters a continuous aeration tank, from there it decant into the DAT ( decant aeration tank ). The DAT is where my stages happen. The manufacturer has set up the timings : aeration for 2 hrs, non aeration for 70min. There are 2 decant per day. My settled sludge volume 30min test shows 90%. We remove sludge from this plant via a truck, which connects to a single outlet 80 mm camlock fitting. Approx 10,000 is drawn from tank. Internal tank pipe work is unknown , potentially outlet is just that and no network of pipe at tank bottom to when withdrawing which will mean a small area of sludge is withdrawn  and mainly just fluid, this would make sense as I have withdrawn 20,000 Ltrs of "sludge" but have seen no shift in SSV. Settling characteristics of the sludge test = very poor flow formation, similar to soup consistency. The 10% supernatant from SSV is clear. The CAT tank SSV has very good settling characteristics/floc formation. Today's pH was - CAT=7.09 DAT=6.97. Not too sure if this brief description will give you a head start up but hope it does.  Thanks again

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Thanks very much Don. You have given me some good information there. There was no form of pH control at this plant. The last 2 weeks I have been manually dosing hydrated lime for mainly alkalinity but also for pH , as well as NaOH. The SBR is set up like this : sewer enters a continuous aeration tank, from there it decant into the DAT ( decant aeration tank ). The DAT is where my stages happen. The manufacturer has set up the timings : aeration for 2 hrs, non aeration for 70min. There are 2 decant per day. My settled sludge volume 30min test shows 90%. We remove sludge from this plant via a truck, which connects to a single outlet 80 mm camlock fitting. Approx 10,000 is drawn from tank. Internal tank pipe work is unknown , potentially outlet is just that and no network of pipe at tank bottom to when withdrawing which will mean a small area of sludge is withdrawn  and mainly just fluid, this would make sense as I have withdrawn 20,000 Ltrs of "sludge" but have seen no shift in SSV. Settling characteristics of the sludge test = very poor flow formation, similar to soup consistency. The 10% supernatant from SSV is clear. The CAT tank SSV has very good settling characteristics/floc formation. Today's pH was - CAT=7.09 DAT=6.97. Not too sure if this brief description will give you a head start up but hope it does. 

Thanks again