|M.Sc Student||Ehud Pisanty|
|Subject||Analysis of the Relations between Construction or Upgrading|
Municipal Wastewater Treatment Plants, WWTP, Costs
and their Design Capacity
|Department||Department of Civil and Environmental Engineering||Supervisor||Full Professor Friedler Eran|
This paper analyses the relation between the construction cost of municipal wastewater treatment plants and their designed plant capacity in Israel. The analysis takes into consideration the type of treatment, that affects the effluent quality. Establishing the relation between construction costs and design capacity can be an important tool both for planners / designers and for evaluation of applications for state support.
The analysis revealed that construction costs in Israel are not very sensitive to effluent quality,within the type of WWTP analysed (i.e. effluent quality of BOD/TSS of 20/30 to 10/10), with construction costs of WWTP producing higher quality effluent are, on average, only about 25% more expensive than lower quality producing ones.
The relative costs of civil engineering; electro-mechanical equipment; and electricity and control change with WWTP size: The relative cost of civil engineering decreases when WWTP capacity increases, while the relative cost of electro-mechanical equipment increases with WWTP capacity increase. The relative cost of electricity and control almost does not change with wwtp capacity.
Treatment cost is composed of capital cost (construction cost with the interest through the loan extent) and of operation and maintenance cost (O&M). Published data show that treatment cost increases steeply with effluent qualities produced by tertiary wastewater treatment technology or better.
In Israel government aid for wastewater treatment is in the form of subsidized loans for plant construction, while no support is given to WWTP operation. Thus, the local authority which is in charge of building and operating the WWTP does not have an incentive to improve effluent quality to a level better than the minimum required by law. On the other hand, it would be of public interest to maximize water reuse, practically these effluents would be directed mainly to agriculture. To increase the variety of reuse possibilities (in agriculture and possibly in other sectors), effluent quality should meet better health standards. This can be achieved without a significant increase in construction cost, but with higher operation costs. Thus, it is recommended that government aid should include not only construction cost but also a subsidy dependent on effluent quality.