References of "Schmitt, Theo G."
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailSludge digestion instead of aerobic stabilisation – a cost benefit analysis based on experiences in Germany
Gretzschel, Oliver; Schmitt, Theo G.; Hansen, Joachim UL et al

in Water Science & Technology (2014)

As a consequence of a worldwide increase of energy costs, the efficient use of sewage sludge as a renewable energy resource must be considered, even for smaller wastewater treatment plants (WWTPs) with ... [more ▼]

As a consequence of a worldwide increase of energy costs, the efficient use of sewage sludge as a renewable energy resource must be considered, even for smaller wastewater treatment plants (WWTPs) with design capacities between 10,000 and 50,000 population equivalent (PE). To find the lower limit for an economical conversion of an aerobic stabilisation plant into an anaerobic stabilisation plant, we derived cost functions for specific capital costs and operating cost savings. With these tools, it is possible to evaluate if it would be promising to further investigate refitting aerobic plants into plants that produce biogas. By comparing capital costs with operation cost savings, a break-even point for process conversion could be determined. The break-even point varies depending on project specific constraints and assumptions related to future energy and operation costs and variable interest rates. A 5% increase of energy and operation costs leads to a cost efficient conversion for plants above 7,500 PE. A conversion of WWTPs results in different positive effects on energy generation and plant operations: increased efficiency, energy savings, and on-site renewable power generation by digester gas which can be used in the plant. Also, the optimisation of energy efficiency results in a reduction of primary energy consumption. [less ▲]

Detailed reference viewed: 125 (2 UL)
Full Text
Peer Reviewed
See detailSludge digestion instead of aerobic-stabilisation – a cost-benefit analysis
Gretzschel, Oliver; Schmitt, Theo G.; Hansen, Joachim UL et al

in Proceedings of the IWA-conference ‘Asset Management for enhancing energy efficiency in water and wastewater systems’ (2013)

The consequences of a worldwide increase of energy costs and an efficient use of the renewable energy resource sewage sludge have to be more and more considered also for smaller WWTP within design ... [more ▼]

The consequences of a worldwide increase of energy costs and an efficient use of the renewable energy resource sewage sludge have to be more and more considered also for smaller WWTP within design capacities between 10 000 and 50 000 PE. To find out the lower limit for an economical conversion into a digester plant, cost functions for specific capital costs as well as operating cost savings were derived. By means of those tools it is possible for the operator of a plant to evaluate if further examinations concerning a refitting of the existing plant to digestion are promising. By comparing capital costs with operation cost savings a break-even point for process conversion could be determined. The break-even point varies depending on project specific constraints as well as assumptions related to future energy and operation costs and variable interest rates. A 3 % increase of energy and operation costs leads to a cost efficient conversion for plant larger than 7 500 PE. Such a conversion of WWTP results in different positive effects on energy turn-around and the operation process of the plant: Increased efficiency by process optimization and energy savings as well as on-site renewable power generation by digester gas which can be used on the plant. Besides, the optimisation of energy efficiency results in an important reduction of primary energy consumption. [less ▲]

Detailed reference viewed: 88 (1 UL)