Cost Analysis of Trickling Filtration and Activated Sludge Plants for the Treatment of Municipal Wastewater Dr. Waleed M. Zahid Associate Professor, Environmental Engineering Civil Eng. Department, College of Engineering King Saud University
Objectives 1- Estimate the costs of wastewater treatment plants employing different biological systems Trickling Filtration Complete-Mix Activated Sludge Oxidation-Ditch Activated Sludge
Objectives 2- Determine the most cost-effective plant
(1) Project cost Wastewater Treatment Costs A- Construction cost of unit processes B- Equipment cost
(1) Project cost C- Other construction costs: o mobilization o Site preparation o Site electrical o Piping o Instrumentation and control o Lab and administration buildings
(1) Project cost D- Non-Construction cost: o Engineering design fee o Legal and technical cost o Inspection cost o Miscellaneous cost o Contingency cost
(1) Project cost E- Land cost F- Profit and overhead G- Interest during construction
(2) Annual Operation and Maintenance Cost A- Labor cost B- material, chemical and energy cost
Methods for Planning-Level Cost Estimating Parametric Costing method Based on statistical analysis of the cost of facilities of similar size and characts. Cost is expressed as a function of some characts. of the process (e.g. flow, surface area) Unit Price Costing Method Unit prices are applied to quantities and sizes calculated from the design of processes (e.g. cost of m 3 of reinforced concrete)
Cost Estimation and Analysis Treatment Schemes Preliminary Treatment Primary Clarification Trickling Filter Secondary Clarifier Chlorination Influent wastewater Final Effluent Thickener Anaerobic Digestion Belt-Filter Press (a) Trickling Filtration Plant
Preliminary Treatment Primary Clarification Complete-Mix Aeration Tank Secondary Clarifier Chlorination Influent wastewater Thickener Anaerobic Digestion Belt-Filter Press Final Effluent (b) Complete-Mix Activated Sludge Plant Preliminary Treatment Oxidation Ditch Secondary Clarifier Chlorination Influent wastewater Final Effluent Thickener Belt-Filter Press (c) Oxidation Ditch Activated Sludge Plant
Cost Estimation The CapdetWorks o A cost-estimating program for wastewater-treatment construction projects o Calculates the design of each unit process based on the process influent and then cost that design
Cost Estimation o The cost estimate the program generates: Planning-level estimate -- Engineering-level estimate
Cost Estimation It estimates costs using the U.S July 2000 data base, and uses cost indices to adjust costs to the present 2006 values The Marshall & Swift Equipment Cost Index The Pipe, Valve, & Fitting Cost Index The Engineering News Record Construction Cost Index 1302 656 7751 Unit costs for some construction activities & material, chemicals, and supplies were acquired from local markets
Other information required by the program Wastewater flows & Characteristics Manfuha WW Treatment Plant Average flow = 200,000 m 3 /d, Peak flow = 320,000 m 3 /day BOD 5 = 300 mg/l, COD = 500 mg/l, SS = 400 mg/l, TKN = 50 mg/l Desired effluent quality Reclaimed water quality criteria for un-restricted irrigation (Ministry of Water & Electricity) Design Criteria for Treatment Processes Design Period = 30 years
Cost Analysis To determine the most cost-effective treatment scheme The Present Worth Cost The Unit Cost per m 3 of wastewater treated The Present Worth Cost The amount of money required at the beginning of the planning period to pay the project cost immediately and the present worth of the annual O & M costs for the entire planning period
SR 1,000,000,000 Unit process construction cost and equipment cost Total construction cost Project cost Present worth 900,000,000 800,000,000 700,000,000 600,000,000 500,000,000 400,000,000 300,000,000 200,000,000 100,000,000 0 Trickling Filtration Complete-Mix Activated Sludge Oxidation Ditch Activated Sludge Comparison of Costs of Treatment Plants
SR 16,000,000 Annual Labor cost Annual material, chemical and energy cost Total annual O & M cost 14,000,000 12,000,000 10,000,000 8,000,000 6,000,000 4,000,000 2,000,000 0 Trickling Filtration Complete-Mix Activated Sludge Oxidation Ditch Activated Sludge Comparison of Operation & Maintenance Costs
Findings & Conclusions 1. The capital and present worth costs for the complete-mix and oxidation-ditch AS plants are higher than those of TF Cost of constructing unit processes and equipment 53% - 62% Project cost 12% Present Worth Cost 18% 70 60 62 53 Complete-Mix AS Plant Oxidation-Ditch AS Plant 50 40 30 31 27 20 13 12 19 18 10 0 Unit process construction and equipment costs Total construction cost Project cost Percent Increase in Costs of the Activated Sludge Plants in Comparison to the Trickling Filtration Plant Present worth
Findings & Conclusions 2. The O & M costs for the complete-mix and oxidation ditch AS plants are higher than those of Tricking filter plant The total annual O & M cost 46% - 52% The annual material, chemical and energy cost 54% - 57% The annual labor cost for the complete-mix plant 30% The annual labor cost for the oxidation ditch 1% 70 60 57 54 Complete-Mix AS Plant Oxidation-Ditch AS Plant 52 50 46 40 30 30 20 10 1 0 Annual labor cost Annual material, chemical and energy cost Total Annual O & M cost Percent Increase in Operation & Maintenance Costs of the Activated Sludge Plants in Comparison to the Trickling Filtration Plant
3. The per unit cost Findings & Conclusions Trickling Filter SR 1.06/m 3 Complete-mix AS SR 1.25/m 3 Oxidation-ditch AS SR 1.23/m 3 The Trickling Filtration is the Most-Cost Effective Treatment Plant (satisfies effluent requirements with the lowest cost)
Thank You