Normally suggest you feed the ...

Published by

Normally suggest you feed the bacterial with a readily biodegradable substrate such as Molasses or even Sugar. I have seen cases where plants have used animal feed to provide nutrient balance. Aerate to supply oxygen and mixing. I would suggest you limit your normal feed as much as possible to allow the recovery to take shape. Check the activity level by switching off the air for a short period and measuring the rate of dissolved oxygen decline before settlement starts to impact the DO level. If your plant has gone Anaerobic you may find the Ammonia levels are currently high and as the plant recovers you may start to lose akalinity due to Nitrification (although unlikley to be a problem if the pH remains between 4 and 5). You will therefore need to have Alkaline materials such as lime or caustic soda available to add. Agree with previous suggestion that you should have some anti-foam and be prepared to go to on / off aeration if foam generation is too high. Then you will need to careful as you re-introduce normal feed materials. If the pH drops back to 4-5 quickly you may shock the bacteria. Slowly increase the amount of normal feed and reduce the readily biodegradable substrate. 

1 Comment

Thanks Michael . I am guessing pinfloc or deflocculation is happening due to firstly my pH's and for how long it has been operating in these conditions for (3-4years) and from the settling characteristics I see in my 30min sludge test. It will settle from 1000ml to 900ml after 30 and have the consistency of thick soup. The start point for me is to get my pH's correct. Finally, today I saw a pH of 7.02 & 6.97, and I have installed a dosing pump for NaOH to removed  manual dosing and ensure a consistent steady dose rate. Lime is being added for alkalinity.

Is there a formula for dosing of CaOH hydrated lime that you know of ?

thanks for your help  

Published by

Permalink

1 Comment

Hi Chris. With regards to alkalinity dosing depends on what you are trying to achieve. If you are removing ammonia you need 7.2mg of Alkalinity per 1 mg of Nitrogen removed. SBR's will normally have an anoxic section which can recover alkalinity in the system if some dissolved BOD is left leaving a nett requirement of approx 4mg/l. However your influent may be having a big impact if it is acidic. Best way to control alkalinity is standard pH control loop dosing in the NaOH and then checking actual alkalinity on a daily basis. If Nitrifying suggest a target alkalinity around 500mg/l. 

The settlement rate you have shown above is really poor and you are probably correct that your low pH level is causing the floc binders to split apart - however if it is a thick soup its likely to also be build up of significant trash and possibly non-organic solvents or even bacterial slime. It would be worth doing an MLSS test followed by vMLSS to see how much of your sludge is organic. If you can't empty and restart the SBR you are looking at a long slow road to recovery but it is feasible. You have made a great start with getting the pH working. If possible speed up the process by putting one basin into manual and continously aerating with the Nutrient make up I previously recommended. This basin can then act as the seed basin for your other SBR's. 

Published by

Permalink