The current factory operates almost 365 days per year, due to some changes in the production plan, there will be inconsistent raw water coming in to the WWTP. As the system is biological treatment, i would like to know the current practices of other WWTP on how to tackle the issues of:
a) inconsistent food supply for the bacteria (what kind of food/ nutrients can be used)
b) how much DO should be supplied to the idle tank if there is no food supply? (any alternative ways to keep the bacteria alive).
c) how often should we do seeding of the bacteria in WWTP? (what kind of parameter should be used as indicator)
Thank you very much for your attention.
Most probably it will be suffcient just to reduce the sludge withdrawal.
What is you design SRT and design Temperature?
Is the plant designed for carbon removal only or also nutrient removal ?
Dear Daphne Ling, you can try the links below:
https://books.google.iq/books?hl=en&lr=&id=41JButufnm8C&oi=fnd&pg=PA1&dq=biological+wastewater+treatment+system&ots=nSF0i-xF-k&sig=CUtmQFMRLMUIm-AZK5LWdPtURGo&redir_esc=y#v=onepage&q=biological%20wastewater%20treatment%20system&f=false
How long will be the period of no-flow? What is the current hydraulic retention time and sludge age? As Kim asked above, will it be COD removal only, or with nitrification, or with N & P removal?
A 20 day+ SRT in an oxidation ditch recovered 'quickly' after being disconnected for around 3 days from the sewage flow. I don;t have numbers to quantify 'quickly.' The site was already stressed and failing to nitrify, so the main function was COd treatment.
Kim Helleshoej Soerensen
It is the sequential batch reactor. The plant is designed to remove BOD, COD, TSS, O&G and nutrients (organic waste from abattoir). The SRT is around 10 days.
Khalid Turki Rashid
Thanks for the reference, will have a look on it.
Jeremy Dudley
1 day per week. The HRT is designed to be 4.71 day, sludge age is around 10 days. Current MLSS 2000-3000mg/L.
We have stop production before and the performance drop, especially pH and MLSS. The effluent was not very satisfying.
i think you need to limit sludge withdraw , and if you can added some nutrient to bacteria in the areation time
If the stop is short i.e. less than a week I would stop wasting and reduce the aeration to have an Oxygen level below 0.5 mg/l to allow simultaneous denitrification since otherwise you risk problems occuring due to low pH and lack of alkalinity. Or you do alternating aeration i.e. 30 minutes with air and 30 minutes with out air.
At a longer stop you should be dosing acetic acid, ethanol or glycol as carbon source and Urea or Nitric Acid as N and Phosphoric acid.
If the stop is short i.e. less than a week I would stop wasting and reduce the aeration to have an Oxygen level below 0.5 mg/l to allow simultaneous denitrification since otherwise you risk problems occuring due to low pH and lack of alkalinity.
The dosing of Carbon Source should give a F:M ratio of approx 0.05 kg BOD/kg MLSS/d and the rest follows the rule of C:N:P of 100:5:1
Mohamed Najemalden
Thanks for the suggestion. I would like to know what kind of nutrients can we add into activated sludge system? Is it preferable to use normal fertilizer (N, P, K) or to use food source (carbohydrate) during the stop period. Thanks.
Kim Helleshoej Soerensen
Sincerely thanks for your feedback. Can i know what kind of carbon source can i use?
In my answer above are are already suggestion for carbon sources i.e. acetic acid, ethanol, glycerol or Glycole.
Also for P source Phosphoric Acid an Nitric Acid or Urea as N source.
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