2012 Water Research Foundation. ALL RIGHTS RESERVED.

Transcription

1 No part of this presentation may be copied, reproduced, or otherwise utilized without permission.

2 Impacts of Cr(VI) Draft MCL on California Water Utilities Mary Messec Smith Research Manager Water Research Foundation

3 Cr(VI) Overview

4 Found in raw and treated water, natural and anthropogenic sources Known human carcinogen when inhaled, possibly when ingested USEPA IRIS risk assessment is under revision Background Included in UCMR3 to obtain national low level occurrence information Currently regulated by CDPH as total chromium at 50 ppb (100 ppb by USEPA) CA 10ppb draft MCL Few effective treatment technologies, only demonstrated in limited WQ conditions Treatment and disposal costs unknown for different conditions Factors impacting Cr(VI) concentrations in DS need research

5 WBA Weak Base Anion Exchange CRM Chemical Reductive Media Cr(VI) Treatment SBA Strong Base Anion Exchange RCF Reduction Coagulation Filtration RO Reverse Osmosis

6 Pros Minimal liquid residuals (limited to backwash water during resin installation) Less operator attention compared to SBA and RCF No additional hazardous chemicals transported to, stored and used at the site (assuming CO 2 and air-stripping used for ph adjustment) Fewer moving parts than SBA or RCF; thus, potentially lower maintenance Requires ph suppression to 6.0 for optimum performance; CO 2 dose estimated at about 2x alkalinity of the water Air-stripping required to raise ph of treated water to acceptable levels (7.5 to 8.0); high noise levels Uranium present in the water will be removed by resin. Uranium on spent resin will reduce disposal options, increase disposal cost CO 2 usage rate likely to be a more costly than either SBA or RCF Cons

7 Pros Mature technology, commonly used for groundwater treatment for the removal of nitrate, arsenic, and other inorganics No ph adjustment required. If brine treatment not required, then no hazardous chemicals transported to, stored and used at the site (except chlorine) SBA treatment likely to be less costly than either WBA or RCF treatment Cr(VI) removal deteriorates with increasing sulfate and nitrate concentrations Generates high-tds waste brine solution with very limited disposal options in most applications If Cr(VI) must be removed from waste brine before disposal, water system will generate solid waste that likely to be a non-rcra California hazardous waste Cons

8 Pros Requires no ph adjustment Does not generate a high- TDS salt brine with challenging disposal options Treatment components are non-proprietary and are commonly used in groundwater treatment Waste backwash water can be discharged to sanitary sewer under most conditions (assuming availability of sewer connection and hydraulic capacity) Requires larger footprint than either SBA or WBA Multiple treatment chemicals are added, including ferrous iron, coagulant, and chlorine Generates significantly larger volume of waste flow compared to SBA or WBA (likely between 2% and 5% of well production) If no sewer available, waste backwash water requires treatment to separate precipitated Cr into solid waste, and recycle recovered water to head of plant; solid waste may be classified as non-rcra California hazardous waste Cons

9

10 Brine Line Brine Recycle Disposal Options Sewer CA Non- RCRA Hazardous Waste LLRW

11

12

13 What s it gonna cost? CDPH Says... Capital investments needed along with the ongoing costs of operations and maintenance are estimated to be $156 million annually for public water systems to comply with this new standard.

14 What s it gonna cost? Research Published in JAWWA Says... $300M-$500M for California utilities

15 Bottom line... Costs are highly dependent on individual circumstances System size Water quality Land cost/availability Disposal options

16 Reality Check? For their treatment costs alone, one California utility projects $780M over the 70-year life span of the 1 cancer case anticipated to be prevented by meeting the MCL.

17 Treatment Evaluate treatment for Cr(VI) under different water quality conditions and potential unintended consequences Cost Develop cost information for Cr(VI) treatment and residuals management Other Investigate impacts of DW treatment and distribution on Cr(VI) concentrations in finished and distributed water

18 Project Number Description Goal Glendale projects, full-scale testing Cost/Treatment 4445 Evaluate SBA/RCF; develop compliance plans Treatment 4449 Determine occurrence; contributions from treatment chemicals 4450 Evaluate WBA/SBA/RCF in 16 WQ; determine cost of compliance Other Cost/Treatment 4488 Evaluate SBA/CRM; brine treatment Treatment 4497 Evaluate speciation in DS; contributions from treatment chemicals and DS; update State of the Science paper 4516 Evaluate RCF/SBA; brine treatment and residuals minimization Other Treatment

19 4450 Treatment types vary by WQ, but Strong Base Anion Exchange (SBA) shows promise for many; residuals management still a major cost factor 4450 Produced a cost estimate tool to help utilities determine potential costs of compliance 4445 (TC) Produced a companion tool to determine best options for grouping sources for combined treatment

20 Questions?