TABLE OF CONTENTS The following variations of the activated sludge process are commonly used in wastewater treatment:
Conventional Activated Sludge
High Rate
Complete Mix
Step Aeration
Extended Aeration
Contact Stabilization
Pure Oxygen
Identify the following design parameters for each process applicable to the treatment of domestic wastewater: percent BOD 5 removal; aeration detention time; F/M ratio; aerator loading; pounds sludge produced/pound BOD 5 removed; oxygen demand (pounds oxygen/pound BOD 5 applied).
Design parameters are summarized in Table 3.1. Values may vary with different operating conditions.
| Process Modification | BOD 5 Removal | Aeration Detention Time (Hours) | F/M Ratio lbs BOD 5/lb MLSS | Aerator Loading 3 lbs BOD 5/1000 ft | lbs sludge/lb BOD 5 removed | lbs O 2/lb BOD 5 applied |
|---|---|---|---|---|---|---|
| Conventional | >85% | 6 8 | 0.2 0.4 | 20 40 | 0.4 0.55 | 1.0 1.1 |
| High Rate | 75 85% | 0.5 2.5 | 0.5 1.5 | 100 400 + | 0.75 1.0 | 0.4 0.5 |
| Step Aeration | >85% | 3 5 | 0.2 0.4 | 40 60 | 0.55 | 1.0 1.1 |
| Contact Stabilization | >80% | 1.5 3.0 | 0.2 0.6 | 50 75 | 0.55 | 1.0 1.1 |
| Extended Aeration | 85 95% | 18 24 | 0.05 0.15 | 12.5 25 | 0.10 0.15 | 1.5 1.8 |
| Complete Mix | 85 95% | 4 6 | 0.2 0.6 | 50 120 | 0.55 0.65 | 1.0 1.1 |
| Pure Oxygen | 85 95% | 2 4 | 0.5 0.9 | 100 250 | 0.45 0.55 | 1.3 1.8 |
A treatment plant is designed using a conventional activated sludge process. Design population is 29,500 and industrial flow is 250,000 gallons per day. Stream standards require an effluent BOD 5 and total suspended solids concentration of 30 mg/l. Based on an analysis of water use records adjusted for infiltration a flow rate of 100 gallons...
