Urban water systems and, in particular, wastewater treatment facilities are among the major energy consumers at municipal level worldwide. Estimates indicate that on average these facilities alone may require about 1% to 3% of the total electric energy output of a country, representing a significant fraction of municipal energy bills. Specific power consumption of state-of-the-art facilities should range between 20 and 45 kWh per population-equivalent served, per year, even though older plants may have even higher demands. This figure does not include wastewater conveyance (pumping) and residues post-processing. On the other hand, wastewater and its byproducts contain energy in different forms: chemical, thermal and potential. Until very recently, the only form of energy recovery from most facilities consisted of anaerobic post-digestion of process residuals (waste sludge), by which chemical energy methane is obtained as biogas, in amounts generally sufficient to cover about half of plant requirements. Implementation of new technologies may allow more efficient strategies of energy savings and recovery from sewage treatment. Besides wastewater valorization by exploitation of its chemical and thermal energy contents, closure of the wastewater cycle by recovery of the energy content of process residuals could allow significant additional energy recovery and increased greenhouse emissions abatement.

Impact on water resources 4.2 Climate Change Impact on Weather 4.2.1 Risks of extreme events and disasters 4.2.2 Economic losses related to weather 50 4.2.3 Extreme weather events 52 4.2.4 The tipping point 58 4.3 Climate Change Impact on Energy 58 4.3.1 Climate impact on energy production 60 4.3.2 Climate impact on energy demand 61 4.3.3 Building more climate resilient energy 61 4.4 Climate Meetings 62 4.4.1

This paper summarises progress of the IAWQ Task Group developing the Scientific and Technical Report (STR) on respirometry in control of the activated sludge process. The significance of respirometry in activated sludge systems is explained from a biochemical background. A classification is proposed which includes all respirometric measuring principles described in the literature. The different respiration rates that can be measured are reviewed and some variables that can be deduced from respiration rate are discussed. Some elementary control concepts will be provided that are necessary for the evaluation of respirometry-based control strategies. Finally, a number of respirometry-based control strategies will be classified and discussed.

No abstract

No abstract