You want to design a pump and treat system to remove nicked from solution as (Ni

Question

You want to design a pump and treat system to remove nicked from solution as (NiS) K_ap = 4 times10^-10. Nickel is present at 4 mx/1 and must be treated to below the drinking water standard of 0.1 mg/l. You intend to use a bioreactor for this which uses sulfate producing bacteria to generate the sulfide you need to react with the nicked. pumping rate is 5 liters/minute. a) Determine the minimum concentration of sulfate necessary for this reaction (in mg/L) b) Assuming all added reacts sulfate react to form sulfide, and all sulfide reacts with nickel, calculate the mass of NiS sludge this reactor would generate on a daily basis. c) SRB need organic carbon (like acetate) to grow and generate sulfide, The theoretical stoichiometric of acetate utilization by SRB is: CH_3COO + SO_4^2+ rightarrow 2HCO_3^- + S^2 + H^+ Calculate the minimum concentration (in mg/l)of acetate you must add to the influent water to have enough organic carbon to generate the sulfide you need.

Explanation / Answer

(a)

Ksp=[Ni2+][S2-]

Ni=4 mg/l

[Ni2+]=4 *10-3g/lit /58.7 g/mol=6.81*10-5 M

[S2-]=4*10-20/6.81*10-5=5.87*10-16 mol/lit=5.87*10-16*32 gm/mol=1.8784*10-14 gm/lit=1.8784*10-11 mg/lit

(b)

[S2-] =5.87*10-16 mol/lit

Ni+S---->NiS

So [NIs]=5.87*10-16 mol/lit*4 lit/min=2.348*10-15 mol/min*90.7589 gm/mol=2.13*10-13 gm/min

So in one day =24 hr=24*60 min=1440 min

So in one day NiS=2.13*10-13*1440=3.0672*10-10 gm = 3.0672*10-7 mg

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