Water and Wastewater.com Help Forums - Sodium bicarbonate addition to anaerobic digester.

IslandHighlander

YaBB Newbies

Offline

Never take Ex-lax
& sleeping pill
on same night

Posts: 12
Nova Scotia Canada
Gender: male

Company or Organization: Halifax Water

Sodium bicarbonate addition to anaerobic digester.
Jan 11^th, 2011, 2:55pm

There has been a bit of discussion here the last few days regarding Sodium bicarbonate addition. We run an anaerobic digester, maybe about 250,000 gal, feeding about 14,500 gal/day. Some time ago we were experiencing a downturn in our alkalinity, and an upturn in our volatile acids. The order of the day was to add soda. We were adding about 10 bags a day for about a week, when our supervisor's supervisor found out and put a stop to it. I myself was never given the actual explanation as to why, but the spirit of the order was to prevent shocking and creating further detriment to our digester condition. Can anyone narrow down what detrimental effects may be experienced by 'over-feeding' soda to an anaerobic digester? Thabks to all who may contribute.

Back to top

IP Logged

sludge judge Hennessy

Ex Member

Re: Sodium bicarbonate addition to anaerobic digester.
Reply #1 - Jan 11^th, 2011, 8:54pm

overfeeding of caustic salts may result in toxicity- it's best to dose over a longer period of time and monitor the acid/alkalinity ratio. Once the acid/ alkalinity ratio is above 0.8 or so the pH will begin to drop and kill the methane formers. Normal process control is to keep it usually between around 0.25 and 0.5.

here's a chart from Wisconsin's DNR certification exam study guide:

SALT MODERATELY INHIBITORY TOXIC

CALCIUM(mg/L) 2500 – 4500 8000
MAGNESIUM(mg/L) 1000 – 1500 3000
POTASSIUM(mg/L) 2500 – 4500 1200
SODIUM(mg/L) 3500 – 5500 8000

http://dnr.wi.gov/org/es/science/opcert/doc/Anaerobic_adv.pdf

hope this helps,

Ryan

Back to top

IP Logged

Sludge Man

YaBB Newbies

Offline

I love Water and
Wastewater.com

Posts: 21

Company or Organization: PT BIOGENIC INDONESIA

Re: Sodium bicarbonate addition to anaerobic digester.
Reply #2 - Jan 15^th, 2011, 9:58pm

Hi IslandHighlander,

By adding caustic soda you can achieve the pH level faster compare to Bicarbonate. But according to our experience by adding caustic soda the alkalinity level drop faster in countertact volatile acid forming in anaerobic system. By adding Sodium bicarbonate the pH level maintain in neutral pH level while alkalinity level still increase. In normal operation, bicarbonate also produced by methane former bacteria to neutralize volatile acid.

Back to top

IP Logged

IslandHighlander YaBB Newbies Offline Never take Ex-lax & sleeping pill on same night Posts: 12 Nova Scotia Canada Gender: Company or Organization: Halifax Water	Re: Sodium bicarbonate addition to anaerobic digester. Reply #3 - Jan 18^th, 2011, 11:12am Thanks for your response. It puts me on the right track. Have a good one.
Back to top	IP Logged

fatih YaBB Newbies Offline Posts: 2 Gender: Company or Organization: Zonguldak Karaelmas University	Re: Sodium bicarbonate addition to anaerobic digester. Reply #4 - Jan 17^th, 2012, 5:44am There has been a gas release in our lab scale digester after adding sodium bicarbonate addition. Is it carbondioxide and whats the reason? Can anyone help me please?
Back to top	IP Logged

Peter_McCarthy Full Member Offline Water and Wastewater.com is the best! Posts: 191 Company or Organization: ADI Systems Inc.	Re: Sodium bicarbonate addition to anaerobic digester. Reply #5 - Jan 17^th, 2012, 6:16pm faith Add more vinegar and stand back!! Islandhighlander More typically one adds sodium carbonate (soda ash) instead of bicarbonate. You can also consider magnesium hydroxide. Peter
Back to top	IP Logged

fatih YaBB Newbies Offline Posts: 2 Gender: Company or Organization: Zonguldak Karaelmas University	Re: Sodium bicarbonate addition to anaerobic digester. Reply #6 - Jan 18^th, 2012, 3:10am It is too late, it took an hour to clean our laboratory We also lost most of the sludge...
Back to top	IP Logged