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Estimation of wastewater treatment costs: Evaluation of the CAPDET model for Canadian conditions
Canadian Journal of Civil Engineering
Abstract
CAPDET is a computer program for estimating construction and operation costs of wastewater treatment plants. A validation study of the model was carried out in order to assess its capabilities for predicting these costs for Canadian conditions. The validation was performed using data from existing full-scale facilities located in Ontario, Québec, and other provinces. The validation study identifies problems in applying the model to Canadian conditions and formulates precise recommendations to account for them. Key results of the validation study were that construction costs can be predicted by the model to within ±20% of the actual costs and operation and maintenance costs to within ±30%. Key words: wastewater treatment plants, construction costs, operation and maintenance costs, CAPDET, computer program.
Emerging technologies for wastewater treatment face an uphill battle to be adopted in practice because no large-scale costing data exists to prove their cost competitiveness. Similar technologies and their costing data offer some insight to the approximate cost, but more detailed estimates are required for a final decision on process selection. The circulating fluidized bed bioreactor (CFBBR) is one such technology, proven at the lab and pilot and scale, but is yet to be used on a large scale. In order to demonstrate the potential economic competitiveness of the CFBBR, a method of modifying the CapdetWorks costing software by first modeling the CFBBR in the GPS-X process simulation software was employed. The modelling was used to determine the necessary changes to a moving bed bioreactor (MBBR) process (media size, density, surface area, and bed fill fraction) in CapdetWorks to simulate the CFBBR and then generate costing estimates for both capital cost (CapEx) and operation and maintenance cost (OpEx). Benchmarking the cost estimates against simulations of conventional suspended and attached growth processes and external costing data from the US EPA was performed to both validate the costing method and analyze the CFBBR's economic competitiveness. The calculation of the net present value from the CapEx and OpEx showed that the CFBBR is predicted to have 10%–30% lower costs at low flows of 1.5 and 4.6 MGD and comparative costs to conventional processes at higher flows from 10 to 30 MGD. Furthermore, the smaller land footprint of the CFBBR-based plants and lower landfilled biosolids implies that the CFBBR's environmental footprint is superior to its competitors and offers advantages for both small-sized plants and large urban plants.
It can be stated that the development and application of CAD/CAE systems in engineering have evolved in parallel with the evolution of computers. However, in the technological field of wastewater treatment there is so far a considerable gap between capability of hardware and software available for simulation and the design of treatment facilities. SIMTAR, a CAD/CAE system, implies an effort to adjust this situation. It is a handy tool for the design and evaluation of wastewater treatment plants -WTP's-. In this system the whole of the stages involved in the design of WTP's (calculation of equipment sizes, cost estimation, and drawing of equipment plants) can be accomplished. The input is done interactively by means of menus and a graphical interface, which allows the user to generate the simulation diagram and the treatment process flowsheet. Results computed by SIMTAR fit quite well with those calculated by several engineering firms for the Manresa and Martorell's plants (Catalonia, Spain).
Pollution control plants regional differences in operating cost data base Technical report No. VP-R-129, prepared for Environment Canada. USEPA. 1978. Design of wastewater treatment facilities-Major systems. United States Environmental Protection Agency (USEPA) Reprint of Department of the Army
- Rupke Associates Ltd
RUPKE & ASSOCIATES LTD. 1982. Pollution control plants regional differences in operating cost data base. Technical report No. VP-R-129, prepared for Environment Canada. USEPA. 1978. Design of wastewater treatment facilities-Major systems. United States Environmental Protection Agency (USEPA). Reprint of Department of the Army, EM 1 1 10-2-501, Septembre 1978, EPA/430/9-79-008.
Program user's guide. United States Environmental Pro-tection Agency (USEPA). U.S. Army Engineering Water-ways Experiment Station, Environmental Engineering Division Evaluation of capital cost data: liquid moving equipment
- D R Woods
- S L Norman
Computer assisted procedure for the design and evaluation of wastewater treatment systems (CAPDET)-Program user's guide. United States Environmental Pro-tection Agency (USEPA). U.S. Army Engineering Water-ways Experiment Station, Environmental Engineering Division, Vicksburg, MS. WOODS, D. R., NORMAN, S. L., and ANDERSON, S. J. 1979. Evaluation of capital cost data: liquid moving equipment. Canadian Journal of Chemical Engineering, 57.