COSTS:

Costs of installing a UV disinfection system will be site specific.

The American Water System (AWS) which operates over 80 water treatment plants is evaluating the possibility of adding UV disinfection to its treatment process. As part of the study, estimated implementation costs are addressed. According to Arora et al. (2001) the estimated O&M costs are $22,600 a year for a 1-MGD facility up to $326,500 a year for a 100-MGD facility. An equation for estimated capital cost is derived.

Capital Cost ($) = $1,766,000 + ($86,950 / MGD) X (Plant Capacity in MGD)

Cost estimates are based on the following assumptions:

1. The reactors provide a UV dose of 40 mJ/cm²
2. The reactors are installed in the filter effluent piping or in high pressure pumping stations

Cotton et al. (2001) estimated the costs of retrofitting water systems with UV disinfection. Cost estimates were developed for flows of 0.024 – 430 MGD (0.09 – 1,628 ML/d). Cost estimates were based on the following assumptions:

1. A UV dose of 40 mJ/cm²

2. LP (Low Pressure) lamps used in systems with flows < 1 MGD (3.8 ML/d)

3. UV disinfection occurs after floc, sedimentation, and filtration and before clearwell storage

4. Three filtered water supplies: low, medium, and high quality relative to UV performance factors

A. Data came from ICR (Information Collection Rule) data base
B. Water Quality Assumptions – parameters given in the table below

Water Quality Assumptions (Cotton et al., 2001)

Parameter	High	Median	Low
UV254 –cm-1	0.014	0.032	0.07
UV transmittance-%	97	93	85
Turbidity-ntu	0.04	0.1	0.3
Alkalinity-mg/L as CaCO3	10	60	140
Hardness-mg/L as CaCO3	20	100	230

5. Interstage pumps required for systems with flows > 1 MGD (3.8 ML/d) at a cost less than 10% of capital costs; small systems had sufficient hydraulic capacity due to low head loss in small UV units

6. A separate building is needed for the UV reactors

7. Equipment redundancy assumed to be a minimum of 20% or a minimum of one redundant reactor (i.e. n + 1 concept).

8. Capital costs amortized over 20 years at 7% interest rate

9. Two UV manufacturers supplied equipment and O&M costs for small systems (<1 MGD). Four UV manufacturers supplied equipment and O&M costs for large systems. Costs used are an average of the costs provided. Manufacturer equipment costs were generally within 40% of each other

10. Engineering estimates and best judgment used for other costs

11. O&M costs included annual lamp replacement for LP and LPHO lamps, semiannual replacement of MP lamps, quarterly calibration of sensors, spare parts, cleaning chemicals, monthly cleaning for systems without automatic cleaning. O&M costs varied significantly by as much as ten fold.

The assumed power costs were $0.08/kW.hr.

Using the cost information for high, median, and low water quality, estimated capital costs for the three water qualities are presented here.

Estimated Capital Costs for Three Water Types

The components used in determining the capital costs and their contribution to each of the three water types are listed here.

Capital Cost Breakdown (Cotton et al., 2001)

Cost Component	Percentage of Total Capital Costs
	Small (0.27 MGD)	Medium (11 MGD)	Large (210 MGD)
UV Equipment	52	20	13
Pumps & appurtenances	NA	10	9
Building	24	9	10
Pipes & valves	NA	4	13
Site Work	NA	10	13
Electrical & instrumentation	8	8	10
Standby power	NA	3	3
Treatability testing	NA	13	3
Engineering	NA	10	11
Contractor overhead & profit	16	6	7
Legal & financial	NA	7	8
Total capital cost	$51,000	$1,200,000	$17,000,000

There was not a significant difference in capital cost between water qualities for larger flows since UV equipment costs are a relatively small percent of total cost because of the larger costs for pumps and a new building.

Using the same cost information, the estimated O&M costs for the three water types are shown here.

Estimated O&M Costs for Three Water Types

The components used in determining the O&M costs and their contribution to each of the three water types are listed here.

O&M costs breakdown (Cotton et al., 2001)

Cost Component	Percentage to Total O&M Costs
	Small (0.27 MGD)	Medium (11 MGD)	Large (210 MGD)
Power	27	52	61
Labor	30	11	7
Parts	43	37	32
Total capital cost	$2,700	$23,000	$290,000

A graph presenting the estimated total unit cost for each of the three water qualities is shown below.

Estimates for Total Unit Costs for Three Water Types

Unit costs decreased with size due to economies of scale and because costs were based on average flows; thus smaller systems need greater relative peaking capacity.

The table below summarizes the capital costs and O&M costs for small, medium, and large systems with median quality water.

Costs for Median Quality Water (Cotton et al., 2001)

System	Capital Costs	O&M
Small (0.27 MGD, 1 ML/d)	$51,000 - $60,000	$2,700 - $3,300
Medium (11 MGD, 41.6 ML/d)	$1.1 - $1.4 Million	$19,000 - $39,000
Large (210 MGD, 794.9 ML/d)	$16 - $22 Million	$170,000 - $600,000

O&M cost varied significantly between water qualities for higher flows due to additional lamps needed, labor, and chemicals for cleaning.

UV disinfection is also 40 – 80% less expensive than ozone for Cryptosporidium inactivation. However, ozone will also oxidize Fe, Mn, and organics and disinfect viruses, and multiple water quality objectives need to be considered in a site-specific cost analysis.