Β1.0 Wastewater and Sludge Management

Detailed design of wastewater treatment plants (WWTPs) including process calculations, equipment selection and general layout of a WWTP.Specific topics covered are: EC Directive 91/271 for wastewater treatment and disposal, preliminary and primary treatment design, activated sludge for carbon, nitrogen and chemical and biological phosphorous removal, design of aeration systems, sludge thickening, anaerobic sludge digestion, biogas utilization for sludge mixing and energy recovery, sludge dewatering and disposal. A WWTP design project will be conducted by each student. The above topics are described in more detail below:

1. Wastewater treatment objectives, current European legislation for wastewater collection treatment and disposal. Municipal wastewater flowrates and characteristics. Overall design considerations. Design of facilities for preliminary and primary wastewater treatment.
2. Microbial growth kinetics.Suspended growth biological treatment, aerobic and anoxic heterotrophic bacteria and aerobic autotrophic bacteria growth. Simple mathematical modelling of activated sludge system using mass balances. Activated sludge design for carbon and nutrient removal, secondary settling tanks design
3. Aeration requirements, oxygen transfer and mixing requirements in activated sludge systems. Mechanical surface aerators and diffused aeration. Principles of aeration system sizing, air supply system, selection of diffusers and blowers.
4. Design of facilities for the treatment and disposal of sludge. Sludge characteristics, primary and secondary sludge. Sludge thickening, gravity and mechanical thickening. Sludge stabilization, anaerobic sludge digesters design, biogas production collection and storage. Digestion heating and mixing requirements. Energy and solids balances in anaerobic digestion. Mechanical sludge dewatering
5. Each student conducts and submits at the end of the semester a WWTP design project that includes: Principles of integrated wastewater treatment facilities design. Site selection and plant layout according to site topograpy. Preliminary plant hydraulic considerations, wastewater and sludge treatment facilities arrangement, tank geometry, equipment selection, provisions for future expansion. Administration, staff and other support facilities.