- Y = 0.5 kg / kg
- kd = 0.05 1 / day
- The volume of the reactor
- The mass and volume of solids that must be wasted each day
- The recycle ratio
"Reactor Volume"... "Excess Solids"... "Mass Balance"... |
- The total number of person : (550 home)(2.9 person/home) = 1,595 person
- The corresponding average flowrate : (1,595 person)(0.230 m3/person.day) = 366.85 m3/day
- The corresponding peak daily flowrate : (366.85 m3/day)(2.5) = 917.13 m3/day
- The average BOD5 load : (1,595 persons)(80 g BOD5/person.day) = 127,600 g BOD5/day
- The corresponding BOD5 concentration : (127,600 g/day) / (366.85 m3/day) = 348 g/m3 (mg/L)
- The average SS load : (1,595 persons)(90 g SS/person.day) = 143,550 g SS/day
- The corresponding SS concentration : (143,550 g/day) / (366.85 m3/day) = 391 g/m3 (mg/L)
- The peak daily BOD5 load : (127.60 kg BOD5/day)(2.5) = 319.00 kg BOD5/day
- The peak daily SS load : (143.55 kg SS/day)(2.5) = 358.88 kg SS/day
- An extended aeration activated sludge process package plant is selected
- The aeration time : 1.0 day
- The aeration tank volume : (366.85 m3/day)(1.0 day) = 366.85 m3
- The oxygen transfer efficiency : 6 %
- The specific weight of air : 1.26 kg/m3
- The oxygen content : 23.2 %
- The air requirement : (319.00 kg BOD5/day) / (1.26 kg/m3)(0.232)(0.06) = 18,187.83 m3/day
- The peak hour factor for the settling tank : 4
- The overflow rate for settling tank : 24 m3/m2.day
- The surface area of settling tank : (366.85 m3/day)(4) / 24 m3/m2.day = 61.14 m2
- The hydraulic detention time for settling tank : 0.5 h
- The volume of the settling tank : (366.85 m3/day)(4)(0.5 h) / 24 h/day = 30.57 m3
1 - Influent flow-rate = 3,800 m3/day | 10 - Concentration of settled sludge = 8,000 mg/L |
2 - Influent suspended solids = 200 mg/L | 11 - Settled sludge specific gravity = 1.02 |
3 - Influent VSS = 150 mg/L | 12 - 60 % of reactor volume will be decanted each day |
4 - Wastewater temperature = 20 °C | 13 - Liquid depth of SBR = 6.60 m |
5 - Hydraulic detention time = 24 h | 14 - Sludge wasting is done once a week |
6 - F/M = 0.1 kg BOD5/kg MLVSS.day | 15 - 65 % of effluent is biodegradable |
7 - MLVSS/MLSS = 0.80 | 16 - BOD5 = 0.68 BODL |
8 - Y = 0.65 kg/kg | 17 - BODL of one mole cells = 1.42 times of X |
9 - kd = 0.05 1/day | 18 - C : N : P is suitable |
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- Biodegradable portion of effluent biological solids = (0.65)(20 mg/L) = 13.0 mg/L
- Ultimate BOD of the biodegradable effluent solids = (13.0 mg/L)(1.42 mg/mg) = 18.5 mg/L
- BOD5 of effluent suspended solids = (18.5 mg/L)(0.68) = 12.6 mg/L
- Influent soluble BOD5 escaping treatment = 20.0 mg/L - 12.6 mg/L = 7.4 mg/L
- Tank volume = (3,800 m3/day)(1.0 day) / 0.60 = 6,333.33 m3
- MLVSS = (3,800 m3/day)(250 g/m3)(10- 3 kg/g) / (6,333.33 m3)(0.1 kg/kg.day) = 1,497 g/m3
- Total SS in the reactor = (200 - 150 mg/L) + (1,497 mg/L) / 0.80 = 1,921 mg/L
- The mass of VSS in the reactor = (6,333.33 m3)(1,497 g/m3)(10-3 kg/g) = 9,481 kg
- The total mass of SS in the reactor = (6,333.33 m3)(1,921 g/m3)(10-3 kg/g) = 12,166 kg
"Mass of SS in the Reactor"...
"Solid Production"...
- The net mass of VSS in the system at the beginning of 1st day = (0.65)(250 - 7.4 g/m3)(10-3 kg/g)(3,800 m3/day) - (0.05 1/day)(9,481 kg) = 125 kg/day
- The mass of inert SS added in 1st day = (200 - 150 g/m3)(10-3 kg/g)(3,800 m3/day) = 190 kg/day
- The mass of SS at the end of 1st day = 12,166 kg/day+125 kg/day / 0.80+190 kg/day = 12,512 kg
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Parameter | Result | |
Value | Unit | |
Influent parameters | ||
Population equivalent | 45,000 | pe |
Average daily flow | 11,500 | m3 / day |
Average daily flow | 133 | L / s |
Peaking factor | 1.80 | - |
Design flow | 863 | m3 / hr |
Design flow | 240 | L / s |
PWWF | 25,000 | m3 / day |
PWWF | 289 | L / s |
PWWF | 1,042 | m3 / hr |
BOD design load | 3,150 | kg / day |
Aeration tank | ||
F / M | 0.05 | kg BOD / kg MLSS . day |
MLSS concentration | 4,000 | mg / L |
Aeration volume required | 15,750 | m3 |
HRT @ avg flow | 32.9 | hr |
HRT @ design flow | 18.3 | hr |
Approximate tank size | ||
Depth | 4.0 | m |
Width | 35.0 | m |
Length | 112.5 | m |
Secondary clarifier | ||
SVI | 150 | g / mL |
Sludge volume load | 0.06 | m3 / m2 . day |
Surface area required | 8,625 | m2 |
Overflow rate | 0.10 | m3 / m2 . hr |
Diameter | 104.8 | m |
Average depth | 3.5 | m |
Volume | 30,188 | m3 |
HRT @ average flow | 6.3 | hr |
HRT @ design flow | 3.5 | hr |
Sludge handling | ||
Sludge production rate | 0.95 | kg TS / kg BOD |
Sludge production | 2,993 | kg TS / day |
Days storage in aeration tank | 2.6 | by incr. MLSS by 0.5 kg / m3 . day |
Days storage in aeration tank | 5.3 | by incr. MLSS by 1.0 kg / m3 . day |
Volume @ 0.8 % | 374 | m3 / day |
HRT thickener | 18.0 | day |
Volume thickener | 6,733 | m3 |
Height | 4.0 | m |
Diameter | 46.3 | m |
HRT @ 2 % | 45 | hr |
Volume @ 3 % | 99.8 | m3 / day |
HRT | 67 | day |
Dewatering capacity | 15.0 | m3 / hr |
Dewatering duration | 46.6 | hr / week |
Dewatering volume @ 18 % | 16.6 | m3 |
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