Wastewater Treatment Notes

8.1 Treatment processes and impurities removal.

8.2 Treatment train/process flow diagram.

8.3 Physical treatment processes.

8.3.1 Racks and Screens: Purpose, types, and construction (Bar, coarse, and fine screens); design criteria.

8.3.2 Grit chamber: Purpose, construction, and design criteria.

8.3.3 Skimming tank: Purpose, construction, and design criteria.

8.3.4 Equalization tank: Introduction, purposes, and types.

8.3.5 Sedimentation tank: Principle of settling (Type I, II, III, and IV), purpose, types, and design criteria.

8.4 Chemical treatment process: Chemical precipitation (Purpose, mixing, and flocculation).

8.5 Biological (Secondary) treatment process.

8.5.1 Objectives of biological treatment process.

8.5.2 Principles of biological treatment process (Attached and suspended growth processes).

8.5.3 Types of biological treatment process.

8.5.3.1 Sewage filtration, filter types: Intermittent sand filter (Purpose, construction, working, cleaning, merits, and demerits); Contact bed (Purpose, construction, working, cleaning, merits, and demerits); Trickling filter (Purpose, construction, working, cleaning, merits and demerits, types – high and standard rates, recirculation, two-stage filters, design criteria, operational and maintenance issues).

8.5.3.2 Activated sludge process: Principle, construction, and process description; Aeration methods (Design parameters and criteria, secondary clarifier, advantages, and disadvantages); Sludge volume/density index and its significance; Control parameters and operational issues (Filamentous bulking, Foaming and mousse formation, Pin-point floc, deflocculation).

8.5.3.3 Oxidation ponds: Purpose, merits, and demerits of oxidation ponds; Theory of oxidation ponds; Construction of oxidation ponds; Commissioning; Operation and maintenance; Operational issues; Design criteria.

8.6 Sequential batch reactor, membrane bioreactor, and moving bed bioreactor: Introduction, removal mechanism, and application.

8.7 Tertiary treatment system: Mechanism, impurity removal, and application.

8.7.1 Pathogen removal: Disinfection, disc filters, and maturation ponds.

8.7.2 Nutrient removal (Nitrogen and phosphorous): Decentralized wastewater treatment system (Introduction, Mechanism, and uses); Anaerobic baffled reactor; Nature-based treatment system. Constructed wetland (Types based on flow: Surface and subsurface, Horizontal and vertical flow), advantages, and disadvantages.