AEROBIC METHOD

ANAEROBIC METHOD(UASB PROCESS)

Anaerobic Process

Fats, proteins, polysaccharides

Step -1 Facultative & anaerobic bacteria: Very slow for grasses, agriculture residue

Fatty acids, amino acids, sugars

Step -2 Fermentation & beta Oxidation (Grow rapidly)

Simple Organic compounds-- short chain fatty acids, alcohols,

BOD converted to bacterial cells

Step- 3, Methanogenesis Strict Anaerobic Bacteria. Grow slowly (Intolerant to pH & Temp )

CH3COOH ---- CH4 + CO2

UASB Reactor

gas collector

biogasgas dome

inlet point

sludge blanket

sludge outlets

bafflesettlingzone

effluentgutter

deflector

biogas

inlet box

Granules

Removal Efficiencies

TSS 60-80%

BOD 60-70%

COD 60-70%

River Discharge Standards

TSS <50 mg/l

BOD <30 mg/l

Faecal Coliform <10,000 MPN/100 ml

DESIGN OF UASB REACTOR(Case Study of Karnal STP)

WASTWATER DATA USED

FLOW = 40 MLDBOD = 250 mg/LCOD = 400 mg/LTSS = 270 mg/LVSS = 70% of TSS = 189 mg/LInert SS = 270-189 = 81 mg/L

DESIGN PROCEDUREDesign Conditions:

Yield Coef. (Yobs) = 0.01 Kg SS/Kg BOD Upflow Velocity = 0.52-0.58 m3/m2/h or m/h Max Peak Upflow Velocity = 1.5 m/h HRT (Hydraulic Retention Time)= 8-12 Hrs. Height of the Reactor = 5.0 m Volumetric Loading = 0.8-1.2 Kg COD/m3/day Sludge Bed Concentration = 65 Kg TSS/m3 or 65000 mg/L

(Conc. 6.5 %)

No. of Reactors = 4 Nos.

Flow in each Reactor = 10 MLD = 10,000m3/d

= 416.67m3/hr

Peak Factor = 2.25

Peak Flow = 416.67 x 2.25

= 937.50 m3/h

Adopt Upflow Velocity = 0.54 m3/m2/h

Surface Area of the Reactor= 416.67/0.54

= 771.6 m2

Provide Reactor Size = 32 m x 24 m

Check for Peak Upflow

Velocity = 937.50/771.6

= 1.21 m/h < 1.5 m/h

Select Height of the Reactor

(to full-fill Sludge Bed & GLSS)= 5.0 m

Volume of the Reactor = 32 x 24 x 5.0= 3840 m3

Volumetric Loading = Q x COD/Vol.= 10,000 m3/d x 400 x10-3/

3840= 1.04 Kg COD/m3/d, OK

Calculated HRT = 3840/416.67= 9.21 hrs, OK.

Sludge Production

Considerations: A = Yield of biomass is 10 % of BOD degraded B = Fractions of VSS remain: (60 % VSS degraded) C = Inert solids (TSS-VSS) influent

Sludge Production

Expected BOD Removal Eff. = 70%Ash Content in TSS = 30%VSS Content = 70% of TSSNew VSS Produced in BOD rem. = 10% of BOD removed

= 0.1 x 0.7 x 250= 17 mg/L

Sludge Produced (A) = 40,000 x 0.017 kg/m3 = 680 Kg/d

Non-Degradable VSS = 40% VSS= 0.4 x 189= 75.6 mg/L

Sludge Produced (B) = 40,000 x 0.76 kg/m3 = 3024 Kg/d

Ash/Inert SS Received in flow = 30% TSS= 0.3 x 270= 81 mg/l

Sludge Produced (C) = 40,000 x 0.081 kg/m3 = 3240 Kg/d

Total Sludge Production = 680+3024+3240= 6944 kg/d

Methane Generation (COD basis)

Quantity of methane estimated from oxygen equivalent of methane gas.

CH4 + 2 O2 CO2 + 2 H2O. 16 g or 1 mole of CH4 equivalent to 64 g

COD. 1 g of COD = 1/64 mole of methane. 1 mole of methane = 22.4 liters of volume. 1 g COD = 22.4/64 = 0.35 Liters CH4

Energy/Electricity Production

Energy Equivalent of methane 33810 kJ/m3 of methane COD removed 11200 kg/d (70 %) Methane generated = 0.35 x 11200 = 3920 m3/d Energy produced = 3920 m3/d x 33810 kJ/m3 = 1533 KJ/s Theoretical Electricity produced = 1533 KW Efficiency of generator = 10 % - 20 % (generally 10 %) Actual Electricity Produced: 3679 kW-h/d

-Low Energy Consumption-Good removal Efficiencies-Generation of Methane Gas (Energy Recovery)-Small Land Area Requirements-Low Surplus Sludge Production-N,P,K Conc. Are Retained in Treated Eff.-Simple Construction, Operation & Maintenance

Salient Features of UASB Technology

Post-Treatment Options

Final Polishing Ponds Aerated Lagoons Combination of Aerated Lagoon & Ponds Down Hanging Sponged Media System

Final Polishing Ponds (FPP)

Aerobic Ponds having not less than 1 day HRT Water Depth 1.5 m Large area requirements Max. Removal Eff. 50% for TSS, 60 % for Total BOD Algal Growth Sludge Accumulation (desludging is required) No Feacal Coliform removal is expected

View of FPP

Facultative Aerated Lagoon (FAL)

Power is Required for Aerators Water Depth 3.0 to 3.5m Settling Tank is required (Solids-Liquid) Moderate HRT (12 hrs) No Feacal Coliform Removal is expected

View showing FAL