Delta Drinking Water Quality and Treatment Costs

Transcription

1 Delta Drinking Water Quality and Treatment Costs Wei-Hsiang Chen Kristine Haunschild Jay R. Lund With research support from William E. Fleenor 1

2 treatment processes in the Delta South Bay Aqueduct Zone 7 ACWD Santa Clara Water District Contra Costa Canal/ Los Vaqueros North Bay Aqueduct Contra Costa Fairfield Benicia Water District Vacaville Vallejo Southern California Metropolitan Water District of Southern California (MWDSC) Treatment Process Water delivered (mgd) iltration/ eparation Anthracite/Sand GAC/Sand Membranes isinfection Chlorine Chloramines Ozonation Ultraviolet PP DV 2 3 MS J 1 TP 2 21 a Penite ncia 42 b Rinconada Santa Teresa 8 (b) 1 b Randall- Bold 4 b Boll man 75 b NBR 4 a, c Fleming Benicia Hill 1 42 a, b Travis AFB 7 a Robert B. Diemer 52 (a) Henry Joseph J. Jensen Mills 75 a 32 a Robert A. Skinner 3 (a) F.E. Weymou th 52 (a) a Pre, b Intermediate, c Post ozonation use, ()- Under construction SOURCE: CALFED (25) and MWDSC ( )

3 Disinfection Byproducts & Treatment DBPs from Bromide and TOC greatest concern. Technologies to treat TOC & DOC and bromide to prevent DBP formation Alternative disinfection Ozonation (widely used for Delta water) UV irradiation Treatment processes for DBP precursor removal Enhanced coagulation (removes TOC) Adsorption (GAC is common) Membrane filtration (MF/UF, NF, and RO) Magnetic ion exchange (removes NOM and bromide) 3

4 Treatment Method Limits Treatments for Delta water quality conditions to minimize cost within technology limits. Results using state and local studies, and may differ slightly due to site-specific conditions or safety factors. TOC (mg/l) 3-5 Ozone/GAC or Enhanced Coagulation/ Ozone Ozone UV/GAC with/without MIE/UF Ozone/MIE/UF or UV Ozonation assumed as base treatment technology for disinfection and oxidation..3.5 Bromide (mg/l) 4

5 Recent Bromide Concentrations South Delta pumps Contra Costa Canal intake Bromide greatest concern for DBP formation CALFED record of decision (ROD) bromide target concentration of.5 mg/l for public health. North Bay Aqueduct.1 San Joaquin EC, bromide, and chloride show serious salinity problems in the South Delta and San Joaquin

6 Recent TOC and DOC Concentrations Contra Costa Canal intake South Delta pumps Has potential to react with chlorine and ozone to form DBPs High level of organic carbon increases amount of disinfectants required. North Bay Aqueduct San Joaquin NBA at Barker Slough has a higher TOC/DOC concentration than other selected Delta locations.

7 and future water quality conditions at Delta intakes Concentration of constituents (Low, Average, High) Location Time Conductance (EC, µs/cm) Bromide (mg/l) Chloride (mg/l) TOC (mg/l C) DOC (mg/l C) (23-27) 73, 155, 232,.1,.2 2,, 1 1.4, 2.4, , 2., 4.3 San Joaquin (23-27) 19, 3, ,.25,.48 8, 71, 1 2.7, 4.8, , 3.7, 9. North Bay Aqueduct (23-27) 13, 299, 572 N.D.,.4,.9, 2, 5 2.7, 7.9, , 5.5, 15.9 South Delta pumps at Banks (23-27) 5, 355, 71,, 455, 11, 741, 2.3,.15,.41.3,.1,.85.3,.5, , 52, 13 11, 8, , 152, 5 1.9, 3.8, , 3.2, 8.2 W Is. Fail 21, 439, 729.,.25,.49 18, 7, 149 Contra Costa Water District (23-27) 151, 497, 151, 79, , 1153, 33.3,.25,.79.3,.45, ,.84, 2.7 1, 84, 217 1, 137, 472 1, 25, 8 2.2, 3.5,.3 2.1, 3.3,.5 W Is. Fail 183, 7, 14.4,.39,.77, 118, 234 Record of ision (ROD) target concentration

8 Treatment Costs for Future Conditions Sea level rise and western island failure increases total costs to treat Delta water. Most likely treatment processes and costs in bold. Some treatments might be impractical. UV or additional treatment technologies might be needed. Plant /Intake Location (Medium plant) (Large plant) CCWD South Bay (South Delta export) Southern California (South Delta export) Condition All All (23-27) W is. Fail (23-27) W is. Fail (23-27) W is. Fail Enhanced Bromide coagulation (mg/l) /Ozone Estimated costs ($/AF) In combination with GAC In combination with MF/UF In combination with MIE/MF /UF In combination with NF

9 Conclusions Contra Costa Canal intake has highest treatment cost increases. Treatment cost difference between South Delta and will increase from $2 - $/af to $1 - $5/af. With 1.5 million af/yr use, treatment cost difference increases from $3 - $9 million/yr currently to $2 - $1 million/yr in the future. Residual health risks may significantly affect selection and operation of water treatment. Plant/Intake location (Medium plant) (Large plant) CCWD (Contra Costa Canal intake) South Bay (South Delta pumps) Southern California (South Delta pumps) Annualized treatment cost ($/af) (23 27) ft SLR ft SLR W Is. Fail