Wastewater Denitrification-II

SOLUTION

1. 10 MLD of wastewater is to be denitrified, and glucose (C₆H₁₂O₆) is to be added for this purpose to the denitrification tank. Nitrate concentration influent to the denitrification tank is 40 mg/L (as N). q_c = 3 days, q = 2 hours. Calculate the effluent nitrate concentration and glucose requirement in Kg/d. (Y_T)_DN = 0.8; (K_s)_DN = 0.1 mg/L; (K_d)_DN = 0.04 /d; (q_m)_DN = 0.5/d. All bio-kinetic constants are in terms of Neglect nitrogen incorporation into bio-mass.

Hint:

· Glucose consumption is due to both energy requirement for denitrifying microorganisms and bio-mass growth

· Bio-mass Formula:

· Balanced equation describing nitrate reduction to nitrogen gas with glucose as electron donor has to be formulated and used.

SOLUTION:

BSRT (q_c) = 3 days;

Therefore,

Also, ;

or, ; Also,

Also,

Therefore, X = 992 mg/L

V = q.Q =

Sludge produced per day =

Bio-mass Formula is ; Formula Weight = 113

i.e., 113 g bio-mass has 5 moles of carbon

Therefore, 275 g of bio-mass has moles of carbon

275 Kg of bio-mass has 12194 moles of carbon

Influent nitrate loading =

Effluent Nitrate =

Nitrate conversion = 400 – 14 = 386 Kg/d

Equation for nitrate conversion:

i.e., 336 Kg of nitrate-N requires 30000 moles of carbon

386 Kg of nitrate-N requires of carbon

i.e., total carbon requirement per day = 12194 + 34464 = 46658 moles

6 moles of carbon = 180 g glucose

46658 moles of carbon =

Glucose requirement is 1399 Kg/d