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TDS

Outline. What is TDS and chloride?Why is the study being conducted?What approaches are being considered?What do we know about TDS and chloride in Iowa streams?TDS and chloride study designResults from the studyWhat is planned next?. Total Dissolved Solids (TDS) ? measure of all constituents d

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TDS

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    1. TDS/Chloride Study Impact of Point Source Outfalls on Receiving Streams Cooperative Study by Iowa Water Pollution Control Association Wastewater Facilities Across Iowa Iowa DNR – Water Quality Bureau Iowa DNR – Watershed Monitoring and Assessment Program

    2. Outline What is TDS and chloride? Why is the study being conducted? What approaches are being considered? What do we know about TDS and chloride in Iowa streams? TDS and chloride study design Results from the study What is planned next?

    3. Total Dissolved Solids (TDS) – measure of all constituents dissolved in water primary anions – carbonates, chlorides, sulfates, nitrates primary cations – sodium, potassium, calcium, magnesium Elevated levels of TDS and chloride in streams can be harmful to aquatic life and a concern for livestock watering use Sources – natural sources from rocks and soils, sewage, urban and agricultural runoff, effluent from wastewater treatment plants, road salting

    4. What prompted this study? Environmental Protection Commission directed the Iowa DNR to develop an economic analysis for the TDS and chloride revision. Sample and monitor chloride and TDS to provide adequate data. Monitor aquatic ecosystem impacts through biological surveys. Review stream classifications to be sure that the uses of streams are properly classified.

    5. Current/Previous TDS and chloride standards in Iowa Chloride – drinking water standard of 250 mg/L; no standard for aquatic life protection TDS – In Iowa prior to 2004, TDS could not exceed 750 mg/L in any water body with a flow rate equal to or greater than three times the flow rate of any upstream point source discharge Since 2004, site specific approach adopted. If TDS >1,000 mg/L at either the mixing zone or zone of initial dilution, Whole Effluent Toxicity Tests required.

    6. Standards being considered? Possible Approaches Adopt numerical criteria - Chloride – 230 mg/L (chronic) and 860 mg/L (acute) - TDS – 1,000 mg/L (chronic and acute) - Levels for preventing chronic toxicity effect need to be met at the end of the mixing zone. - Levels for preventing acute toxicity effect need to be met at the end of the zone of initial dilution. - Values used to trigger toxicity tests Eliminate TDS, go with specific ions - chloride, sulfate, others? OTHER APPROACHES?

    8. What are typical TDS and chloride concentrations in Iowa streams?

    15. Point source outfalls can be a major contributor of TDS and chloride to streams, especially during low-flow conditions Need for data from point source outfalls in order to establish realistic standards Data need to be collected under low-flow conditions Study conducted by IWPCA, wastewater treatment facilities across Iowa, and the Iowa DNR

    16. Two Phases to Data Collection Pilot Study - 21 facilities sampled during winter, low-flow conditions during a 2-week period in 2005 Full Study - 100 facilities sampled during late summer/early fall, low-flow conditions during a 6-week period in 2005 Participation in study was voluntary

    17. Pilot Study Site Selection Iowa Water Pollution Control Association and Iowa DNR identified communities that might be adversely affected by levels of TDS and chloride under discussion

    18. Pilot Study Sampling Design / Site Selection Samples collected during late winter, low-flow conditions (February 21 through March 6, 2005) All facilities that are not controlled discharge lagoons Final Effluent Grab Final Effluent 24-hr Composite City Tap Water Upstream of Plant Outfall Downstream of the Plant Outfall Controlled discharge lagoons sampled final effluent grab, city tap water, upstream of plant outfall (3 sites) Samples analyzed by Keystone Laboratories Outfall flow recorded when effluent grab sample collected Sampling frequency ranged from 1 to 14 days

    22. Full Study

    23. Sampling Design / Site Selection Full Study Samples collected from a representative subset of Iowa wastewater dischargers. Samples collected August 22 through September 28, 2005 All facilities that are not controlled discharge lagoons - 5 sample sites Controlled discharge lagoons - 3 sample sites Samples analyzed by ARDL, Inc. (Mt. Vernon, IL) Outfall flow recorded at time final effluent grab collected

    35. What is planned next? Results from the pilot and full study finalized and provided to the DNR – Water Quality Standards. DNR Water Quality Standards staff are developing scientific based TDS and chloride criteria based on available toxicity data. TDS/chloride numerical criteria will be developed based on all available data. Once criteria established, an economic analysis will be completed to determine the cost for facilities to meet proposed criteria. Stakeholder and Technical Advisory meetings will be held to gather input and comments on proposed criteria. Any proposed water quality standards will need EPA approval and consultation with the USFWS for endangered species.

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