Arsenic Treatment The rest of the story Texas Commission on Environmental Quality October 25, 2005 Presented to: Russell Fisher Turnstone Services The Woodlands, Texas (281)

The Commercial Perspective Locate prospects – anticipate the unmet need Qualify Prospects – gather data to understand need Propose Solution - Satisfy customer’s need Turnstone Services

The Need - Arsenic Treatment Objectives Achieve compliance Conserve the water resource Develop Arsenic Treatment Strategy Associated regulatory issues Technology Constraints Unanticipated Consequences Define the Need – Gather Information Water Quality Data - TCEQ Usage information - PWS Turnstone Services Aquifer characteristics

Turnstone Services Texas Groundwater is a Dynamic System Sandstone Aquifers – highly variable over short dist Intermittent Recharge – year to year rainfall variance Regional climate variation – fluctuating water levels Coastal faulting and subsidence Geochemistry - the rock/water system

Understanding the Environment pH - activity of the hydrogen ion Eh – electrode potential, activity of the electron Turnstone Services Ca/Mg – hardness, scale forming pH sensitive Indicator Species TDS - may require lowering of salt content Cl - – major contributor to TDS HCO 3 - – contributes to TDS, limits F trmt

Arsenic (As)toxic regulated under the CWA Iron (Fe)essential nutrient, contributes to color and taste Manganese (Mn)contributes to color and taste Sulfide (H 2 S)contributes to odor, toxic at high concentration Uranium (U)radiation source, toxic Silica (SiO 2 )non regulated, foulant for membrane processes Fluoride (F)beneficial at low concentrations, regulated The lesser know elements of water chemistry Turnstone Services

Std E 0 (Volts) Oxidized form Reduced form 1.23MnO 2 Mn SeO 4 -2 H 2 SeO NO 3 -1 HNO Fe +3 Fe H 2 SeO 3 Se 0.58H 3 AsO 4 HAsO H 2 MoO 4 MoO VO +2 V UO 2 +2 U SO 4 -2 SO SH2SH2S Oxidized Sand Reduced Sand Turnstone Services Common Redox Species In Ground Water

Fe 2 O 3 FeS 2 As 2 O 3 As 2 S 3 MoS 2 HAsO 4 - MoO 4 -2 UO 2 UO 2 +2 H 3 AsO 3 H2OH2O O2O2 Groundwater Redox Front Turnstone Services

Importance of redox potential Redox affects acid-base behavior, i.e. charge Redox state often dictates solubility Redox reactions affect pH Fe(+III) insoluble, Fe(+II) low to moderate solubility U(+IV) insoluble, U(+VI) highly soluble H 3 AsO 4 mild acid, H 3 AsO 3 weak acid Ionization of weak acids: HCO 3 -1, H 4 SiO 4 HNO 3 strong acid, HNO 2 weak acid

Turnstone Services Typical Treatment Strategies AsAbsorption As, TDSR/O or R/O + Absorption Ratio dependent As, Fe, Mn, S -2 Adsorption + Catalytic Oxidation As, TDS, FR/O Fe, Mn, S -2, UCatalytic Oxid + Adsorption Rule #1: Match the Solution to the Problem

Turnstone Services Summary Understand geological setting – aquifer type, mineralogy Analyze water sample for less known species Interpret water analysis in context of aquifer geochemistry Apply technologies that best address the problem