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RE: bioassy motality using sodium bisulfite

Rob Baur — Tue, 05 Feb 2008 12:42:09 GMT

We use a feedback loop using an on line analyzer like http://analyticaltechnology.com/cms/Default.aspx?tabid=89 It is relatively cheap and uses diluted sulfuric acid as its only reagent. Be sure to install a system to bleach the sample lines automatically as bisulfite residual will grow slime that consumes both bisulfite and reacts with chlorine.

Bisulfite does have a BOD, but chemical DO consumption requires a catalyst like cobalt. Old Std. Mthds. had an aerator test that depressed the DO by adding bisulfite and a cobalt catalyst. Measuring DO drop due to bisulfite on the lab bench showed a DO increase due to the DO probe stirrer. Adding a catalyst dropped the DO immediately.

RE: bioassy motality using sodium bisulfite

rwhitworth52 — Fri, 01 Feb 2008 13:43:00 GMT

Phil,

You are most likely correct about maintaining the D.O. during the toxicity test procedure; it just came to mind about the D.O. depression.

RE: bioassy motality using sodium bisulfite

Phil — Fri, 01 Feb 2008 12:24:11 GMT

Thanks! I thought DO was monitored & controlled at a level of >4.0 mg/l during the 96hr test period.

RE: bioassy motality using sodium bisulfite

rwhitworth52 — Fri, 01 Feb 2008 11:57:40 GMT

Phil,

Using bisulfide for dechlorination is usually 1 part to 1 part. Excessive use of bisulfide will deplete oxygen and kill the test organisms.

bioassy motality using sodium bisulfite

Phil — Fri, 01 Feb 2008 11:51:06 GMT

All,

During our dechlorination agent conversion from SO2 to Sodium Bisulfite,WET bioassay monitoring was conducted with a >50% mortality to the Mysid Shrimp. The lab feels it was due to a overdosing of the bisulfide because only the shrimp was effected which I agree. Anyway, does anyone have experience with the bisulfite dosing? IE enough for chlorine removal but not overdosing.

Thanks,

Phil