Answer Happy

1.9 You have received a flowsheet as shown below and you are required to advise your line manager about the changes that must be made on the flowsheet. Indicate anything that you think is wrong with the flowsheet, explain why this is wrong and what will happen if it remains where it is? (20)
Secondary setting tank Dewatering system Biogas Grit Chamber Disinfection discharge Baloon Row sludge Sludge disposa tank Lagoon pump grit disposal Find film reactor Additional info Molecular Weight: C=12 H=1 O=16 Ca=40.1 Mg=24 . Carbon dioxide CO2 + Ca(OH), CaCO, (s) + H20 Calcium carbonate hardness (CCH Ca(HCO3)2 + Ca(OH), 2CaCO3 (s) + 2H,0 Calcium noncarbonate hardness (CNCH) Caso + Na Co, Caco, (s). Na 50 Magnesium carbonate hardness (MCH) Mg(HCO3)2 + Ca(OH), Caco, (s) + MgCO3 + 2H,0 MgCO3 + Ca(OH) 2 MgOH)2 (s) + CaCO; (s) Magnesium noncarbonate hardness (MNCH) MgSO4 + Na2CO; MgCO3 + Na2SO MgCO3 + Ca(OH), Mg(OH), (s) +CaCO, (s)
Mg2+ -sludge = (Original Mg2+) - (Residual Mg2+) Ca2+ - sludge = (Original Ca2+) + (Lime) - (Residual Ca2+) M=CQ. Calcium will precipitate as Cacoz while magnesium will precipitate as Mg(OH),. Chemical EW (mg/meq) Residual Ca2+ 0.6 CaCO3 50 Residual Mg2+ Mg(OH)2 29.2 0.2 Step 1. Calculate total hardness (TH) as the sum of the multivalent cations. Step 2. Calculate alkalinity (ALK), which is typically the bicarbonate concentration. Step 3. Calculate carbonate hardness (CH) and noncarbonate hardness (NCH). CH= ALK if TH > ALK CH= TH if TH< ALK NCH = TH - CH. Step 4. Determine the hardness speciation. CCH = Ca2+ if Ca2+ <CH CCH=CH if Ca2+ > CH CNCH = Ca2+ - CCH. MCH=CH - CCH MNCH = Mg2+ - MCH.