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Total Dissolved Solids

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Information about Total Dissolved Solids
Business & Mgmt

Published on February 6, 2014

Author: NWFoodProcessors

Source: slideshare.net

Description

What is Total Dissolved Solids (TDS)? Discussed will be environmental and health issues, regulation of TDS in water, behavior of TDS in soil, and treatment of TDS in wastewater and soil. Many Northwest food processors use land treatment to sustainably treat and reuse wastewater. It is an essential part of their operations and in many cases the only option available. Land treatment allows the processors to provide an economical, beneficial reuse of the process wastewater while utilizing the soil and crop system to provide necessary treatment to protect groundwater quality. An understanding of TDS and its role in land treatment system management to protect groundwater quality is necessary to influence appropriate future policy for land treatment operations, permitting, and compliance.
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Total Dissolved Solids: What are they? and How do they affect Land Treatment? Dan Burgard, CPSS Principal Soil Scientist Cascade Earth Sciences January 13, 2014

Introduction  Dan Burgard  Certified Professional Soil Scientist  22 years of Land Treatment Reuse Experience  Cascade Earth Sciences  37 years of Land-based Treatment Consulting  Long time members of NWFPA  Focus on Services to Food Processing  Water supply and Irrigation  Water and Wastewater Treatment  Permitting and Compliance

BACKGROUND  Northwest food processors rely on land treatment systems  Sustainably treat and beneficially reuse process wastewater.  Agricultural crops , natural processes provide necessary treatment to protect groundwater quality.  At least 30 of the 78 NWFPA member facilities employing nearly 4,000 people in Washington state,  Beneficial reuse of process wastewater benefits  Sustainable water source in place of declining groundwater supplies  Expansion or continuation of irrigated agriculture.  Washington Department of Ecology regulates land treatment  Policy statements and permit conditions have been unattainable  preclude land treatment as an option.  Appropriate future policy with respect to land treatment operations, permitting, and compliance is needed

TDS White Paper  Prepared by CES and NWFPA Environmental Affairs Committee  What is TDS?  Environmental and Health Effects  Regulations  Effects on Land Treatment/ Behavior in Soils  Treatment Processes  Best Management Practices  Pollution Prevention  Land Treatment Operations  Points of Compliance

Today’s Presentation  Based on the White Paper  What is TDS?,  Environmental and Health Issues,  Regulations regarding TDS in Water,  Behavior in Soil  Treatment Processes  Best Management Practices  Compliance  Conclusions

What is TDS?  Total Dissolved Solids  “filterable residue”  Inorganic minerals (salts) dissolved in the water  Difficult to treat  Accumulates in soils and groundwater  Dissolved organic compounds  Sugars, soluble starches, amino acids  Soluble BOD- easily treatable  Inorganic fraction of TDS is the subject of the review  Also known as “Salts”

Components of TDS  Cations- positively charged  Sodium (Na+), potassium (K+), calcium (Ca2+), and magnesium (Mg2+)  Small quantities (< 10 mg/L)  hydrogen, strontium, barium, iron, manganese, and other trace metals  Anions- negatively charged  Carbonate (CO32-), bicarbonate (HCO3-), chloride (Cl-), sulfate (SO42-), and nitrate (NO3-)  Small quantities (< 10 mg/L)   nitrite (nitrogen), fluoride, hydroxide, arsenate (arsenic), borate (boron), molybdate (molybdenum), selenate (selenium), and other trace metals Phosphate (phosphorus)

Environmental and Human Health Concerns  Aesthetics  Hardness – calcium, magnesium, carbonate  Hard water deposits, scaling  Taste     Chloride - salty Sulfate – depends on cation and concentration Sodium – noticeable at 200 mg/L Calcium, magnesium often added for taste  Odor  Sulfate => hydrogen sulfide  Corrosion    Sulfate and chloride – concrete and steel Dependent on alkalinity Water without minerals is corrosive

Environmental and Human Health Concerns  Health Benefits  Calcium and Magnesium  Bone structure, muscle contraction, nerve impulse transmission, blood clotting, cell signaling  Calcium  improve bone density  Magnesium  reduced cardiovascular disease  Potassium  nervous system function, blood pressure regulation, carbohydrate metabolism  Sodium  electrical balance nervous system and body fluid maintenance

Environmental and Human Health Concerns  Laxative Effects- temporary  Magnesium  > 125 mg/L  Sulfate  1,000 to 1,200 mg/L  Potassium and chloride  “very high concentrations”  Sodium  electrical balance nervous system and body fluid maintenance

TDS in French Mineral Waters  USEPA drinking water standards:  TDS = 500 mg/L; Sulfate (SO4) = 250 mg/L  Contrex Mineral Water Ca Mg Na SO4 HCO3 TDS 468 mg/L 74.5 mg/L 9 mg/L 1121 mg/L 372 mg/L  Sold as Ca and Mg source for nutrition.  www.contrex.fr  Courmayer Mineral Water Ca Mg Na SO4 HCO3 TDS 565 mg/L 56 mg/L 0.6 mg/L 1477 mg/L 130 mg/L 2170 mg/L  www.eau- courmayeur.com

Environmental and Human Health Concerns  Nitrate (NO3) Toxicity  Drinking water standard = 10 mg/L as nitrogen  Converts to nitrite (NO2) in ruminant animals, susceptible individuals  Inhibits ability of blood to carry oxygen  Susceptible individuals  Infants less than 3 months  Elderly adults  Regular use of anti-acids or acid blockers

Environmental and Human Health Concerns  Sodium Intake  Very common, very soluble  Added by most water softeners (sodium chloride)  No standard for drinking water  120 mg/L suggested by National Research Council  240 mg/d in 2 L (10% of RDA)  Potassium Intake  Not normally a concern. Daily RDA > 3,000 mg  Potential concern for high risk individuals:  Kidney dysfunction, hypertension, diabetes, adrenal insufficiency

Environmental and Human Health Concerns  Agriculture  Essential nutrients for plants  Ca, Mg, K, Na, SO4, Cl, NO3  Soil Salinity  Salts remain after water used  Accumulation hinders water uptake by plants  Crop Toxicity and Tolerance  Some crops sensitive to Na and/or Cl  Citrus, avocado, cane fruits  Leaf burn from sprinkler irrigation with saline water  Soil structure  Sodium disperses soil clay particles, seals soil  Calcium or high salinity prevents negative effects of sodium

Measures of TDS  Total Dissolved Solids  Filtered water is dried in oven; units: mg/L  Good for relatively clean water  Treated effluent, groundwater  Fixed Dissolved Solids (FDS)  Organics in TDS burned off in furnace; units: mg/L  Use for waters with soluble BOD, organic ions  Electrical Conductivity  Opposite of resistance; units: mmho/cm, µmho/cm, dS/m, µS/cm  Easy surrogate for TDS test in water without organic ions  EC µmho/cm x 0.64 = TDS mg/L  Individual Chemical Analysis

Sources of TDS in Food Processing Wastewater  Naturally occurring in water supply  Cutting, cooking, washing food crops  Seasonings, processing chemicals  Brine solutions  Cleaning and sanitation chemicals  Water treatment chemicals  Boilers, chillers, cooling towers, RO units are not sources  Concentrate existing salts

Sources of TDS in Food Processing Wastewater  Calcium, magnesium and potassium  Often from the crops processed  Calcium and magnesium from pH control chemicals  Potassium hydroxide can be used instead of sodium hydroxide  Sodium  Sorting and chilling brines  pH control, cleaners, rock salt for softeners  Chloride  Water softeners, seasonings, sanitation, pH control, cleaning chemicals

Sources of TDS in Food Processing Wastewater  Sulfate  Oxidized sulfur from crops  Sulfuric acid for pH and cleaning, cleaning chemicals  Bicarbonate and carbonate  Carbon dioxide from biological reactions  Alkaline cleaning chemicals  Nitrate  Not common in process wastewater with high oxygen demand

REGULATIONS IN WASHINGTON AND OTHER WESTERN STATES  Land Treatment = Groundwater Quality Protection  USEPA TDS limit in drinking water and most states  Does not regulate groundwater quality but drinking water quality standards for TDS = 500 mg/L  Secondary standard    Undesirable aesthetic properties imparted by the constituents of TDS Will not trigger an enforceable public drinking water emergency Sulfate and chloride are the only TDS constituents regulated separately  250 mg/L, secondary standards  California, Idaho, Washington, and Oregon  TDS is regulated under anti-degradation rules for groundwater quality

REGULATIONS IN WASHINGTON AND OTHER WESTERN STATES  Washington  Anti-degradation rules  All Known, Available and Reasonable Prevention Control and Treatment (AKART)   Applied to all wastewaters prior to discharge to waters of the state. Degradation of groundwater up to the limit possible  Must not harm beneficial uses. All groundwater has potential to be drinking water  Summary:  All groundwater is to be protected to drinking water quality regardless of the primary or secondary designation of the contaminant by EPA

REGULATIONS IN WASHINGTON AND OTHER WESTERN STATES  Idaho  Anti-degradation rules  Two important policies:  Existing and projected future beneficial uses of ground water shall be maintained and protected (IDAPA 58.01.11.006.02)  Prevent contamination of ground water from …contamination to the maximum extent practical (IDAPA 58.01.11.006.05)  Groundwater Designations  “Sensitive Resource” – stricter limits than standards  “General Resource” (essentially all groundwater in Idaho)– limits equal to standards  “Other Resource”- limits may be greater than standards  Summary:  All groundwater is to be protected to groundwater quality standards or better.

REGULATIONS IN WASHINGTON AND OTHER WESTERN STATES  Oregon  Non-degradation rules  All groundwaters…shall be protected …existing or potential beneficial uses for which the natural water quality …is adequate (OAR 340-40-0020 (3))  Existing high quality groundwaters which exceed …legitimate beneficial uses shall be maintained except as provided for in these rules.” (OAR 340-40-0020 (3)  Limits on secondary contaminants such as TDS, chloride, and sulfate are considered ‘Guidance Levels’ and may exceed standards as long as no hazard to human health and the environment.  Summary:  All groundwater is to be protected to groundwater natural water quality. Exceptions allowed for secondary contaminants.

REGULATIONS IN WASHINGTON AND OTHER WESTERN STATES  California  Anti-degradation rules  Water quality objectives established in Basin Plans  Serve as guidelines for beneficial use designations and permit limits  Require discharge EC to be no more than 500 µmhos/cm over source EC.  Presumed low potential to harm groundwater unless groundwater is harmed.  Designated beneficial uses must be maintained on a constituent by constituent basis, not just general TDS.  Exception to EC limit if caused by organics or water conservation results efforts caused the high EC  Salt management plans to show required Best Practicable Control Technology for discharges  Summary:  All groundwater is to be protected to allow designated beneficial uses. All groundwater designated as municipal water supply and agriculture

BEHAVIOR IN SOILS  Fate of salts applied to soil  Accumulate in the soil  Soluble salts  Adsorbed ions  Insoluble compounds  Taken up by plants  Leach from the soil with percolating water

BEHAVIOR IN SOILS  Accumulate in the soil  Dissolved in soil water  Water holding capacity retains excess salts in the water available to plants  This is the salinity of the soil  Reduces ability of plants to remove water from soil  Adsorbed Ions  Soil is negatively charges (cation exchange capacity)  Retains Ca, Mg, Na, K  Repels Cl, NO3, SO4, HCO3, CO3  Precipitate as insoluble  Calcium carbonate  Calcium phosphate  Calcium sulfate  Magnesium carbonate Cation Clay or OM particle

BEHAVIOR IN SOILS  Taken up by plants  Plant essential nutrients (NO3, Ca, Mg, K, Na, Cl, SO4)  Available in the root zone  Plants take what is needed and exclude the rest  Some move with water, some require contact with roots  Uptake is usually far less than application rates Example:  Ca at 40 mg/L in irrigation water, 24 inches of irrigation = 218 lb Ca  Ca in alfalfa at 1%, harvest 12,000 lbs hay = 120 lb Ca  Na at 40 mg/L = 218 lb Na  Na in alfalfa at 0.1%, harvest 12,000 lbs hay = 12 lb Na

BEHAVIOR IN SOILS  Leach from the soil with percolating water  Soil is a sponge, not a sieve  Excess water drains away  Soluble salts and some adsorbed ions drain with it  Move downward in soil, can go to groundwater Wet soil Dry soil Oven-dry Permanent Wilting Point Field capacity Draining

BEHAVIOR IN SOILS  Crop Salt Tolerance  Each crop has a different tolerance for soil salinity Crop Tolerance to Soil Salinity 120 Bean Relative Yield (%) 100 Carrot Corn, sweet 80 Onion 60 Potato Alfalfa 40 Wheat, semi dwarf Fescue, Tall 20 Orchardgrass 0 0 1 2 3 4 5 6 Soil Electrical Conductivity 7 8 9 10

BEHAVIOR IN SOILS  Leaching Requirement  Salts accumulation must be controlled by leaching  A widely accepted formula is: LR = ECiw / (5 ECe - ECiw) (Ayers and Wescot, 1985) where: LR = leaching requirement (% of total water applied) ECiw = electrical conductivity of irrigation water ECe = desired electrical conductivity of soil saturation paste extract

BEHAVIOR IN SOILS  Sodium Considerations  Sodium adsorption ratio (SAR)   Potential to damage soil structure Ratio of sodium to calcium and magnesium in irrigation water  Sodium disperses clay particles  Calcium and magnesium aggregate clay particles  Dispersed clay particles clog soil pores    Prevent water movement Limit root growth Prevent air exchange with soil and atmosphere  High TDS (EC) can mitigate high SAR  Adding calcium to soil or water can mitigate high SAR

Salinity and Sodium Suitability Limits (Ayers and Wescot, 1985) Limitations Slight Moderate Severe Salinity EC mmho/cm <0.7 0.7 – 3.0 >3.0 (affects crop water availability) TDS mg/L <450 450 – 2,000 >2,000 Infiltration SAR (affects water infiltration rate) 0–3 >0.7 0.7 – 0.2 <0.2 (consider SAR and EC) 3-6 >1.2 1.2 – 0.3 <0.3 6 – 12 >1.9 1.9 – 0.5 <0.5 12 - 20 >2.9 2.9 – 1.3 <1.3 20 – 40 >5.0 5.0 – 2.9 <2.9 EC (mmho/cm)

CONVENTIONAL TREATMENT PROCESSES  Systems that separate TDS from the process wastewater  There is always a waste that requires disposal  Best suited to brines and solutions with little or no organic constituents.  Example Processes  Membrane  Thermo-mechanical Evaporation  Crystallizer  Evaporation Ponds  Enhanced Solar Evaporation  Deep Well Injection

CONVENTIONAL TREATMENT PROCESSES  Membrane Processes  Reverse osmosis (RO)  Cross flow membrane filtration  Water is forced across a semi-permeable membrane leaving salts behind    Low pressure and high pressure systems are available Commonly used as an alternative to softening for boilers or cooling towers Produces a saline reject stream containing up to 99% of salts in 15 to 20% of the original flow depending on design.  Electro-dialysis reversal (EDR)  Uses electrical current and specially prepared semi-permeable membranes  Two, flat sheet, stacked membranes with flow channels between   One membrane for cations, one for anions Similar performance to RO although more complex and expensive

CONVENTIONAL TREATMENT PROCESSES  Processes for Brines or Concentrated Reject Streams  Crystallizer  Circulates brine through a heat exchanger to flash evaporate water and force salts to crystallize  Crystallized salts removed in plate and frame filter press  Evaporation Ponds  Ponds built is dry climates that allow water to evaporate leaving salts behind  Requires multiple cells to allow cleaning one while other is evaporating  Enhanced Solar Evaporation  Evaporation pond enclosed like a green house to enhance heat collection  May involve sprinklers or other devices to atomize and vaporize water to enhance drying

CONVENTIONAL TREATMENT PROCESSES  Disposal Option for Brines or Concentrated Reject Streams  Deep Well Injection  Generally used for highly saline waters  Inject water into a deep formation     Saline aquifer Oil well field/ Oil producing formation Deep porous formation High cost     Usually several thousand feet deep where it is not economical to pump water Large bore hole Must pressurize to push water into aquifer or formation Must maintain well to control corrosion and fouling of screen

BEST MANAGEMENT PRACTICES  Key to managing salts in process wastewater  Limit the introduction of salts  Tailored to each facility  Generally, least cost methods for salts control  Limit to what can be done depending on processing steps and sources of salts

BEST MANAGEMENT PRACTICES  Pollution Prevention  Know the sources of salts  Water supply  Soil washed from root crops  Cutting, blanching/cooking in water  Coatings, batters, seasonings  Sorting or cooling brines  Water softener brine discharge  Disinfection, cleaning, or water treatment chemicals  Food preservatives such as sodium sulfite  Other processes might concentrate existing salts  Boilers, chillers, cooling towers, RO processes

BEST MANAGEMENT PRACTICES  Eliminate or Minimize Water Softening  Rock salt adds sodium or potassium and chloride  Replace with RO or other similar process  Isolate Low Flow, High Strength TDS Streams  Boiler blowdown, RO reject  Small and clean enough for efficient treatment and disposal  Improve Solids Removal  Primary treatment of process wastewater  Removes minerals still entrained in food particles

BEST MANAGEMENT PRACTICES  Dry Solids Removal  Sweep and scoop into totes, bins, or hoppers and haul away vegetable matter for animal feed  Locate bins at ends of scrap conveyors  Keeps small scraps with large exposed surface area from water where salts leach out  Utilize Clean-in-Place Where Possible  Flush internal pipelines with cleaning chemicals instead of disassembly and individual parts washing  Saves labor and uses less chemicals and water needed for cleaning and sanitation.

LAND TREATMENT SYSTEM PRACTICES  Best management practices for process wastewater  Following in-plant practices salts are minimized  Must be managed in irrigation cropping and soil practices  Control potential for negative effects on soils and crops  Control potential for negative effects on groundwater

LAND TREATMENT SYSTEM PRACTICES  Apply at Salts Agronomic Rate  Traditional Agronomic Rate is for Nitrogen, Irrigation  Application rate that is required by the crop for grow and be productive and healthy with minimal negative impact to groundwater  Salts application rates exceed crop uptake  Proposed definition  Application rate of salts or concentration that allows healthy productive crops to be grown and soils to be managed to maintain a productive environment for crop growth and controls the impact to groundwater  Can include:  Dilution, reduced loads, appropriate leaching, soil amendments to mitigate sodium, irrigation management to limit excess leaching

LAND TREATMENT SYSTEM PRACTICES  Manage Irrigation to Control Salts Movement  Amount of water applied and climate controls leaching  Greater leaching reduces salts concentration in percolating water  Controlled leaching in arid regions can limit salts movement to groundwater.  Specific Practices for Irrigation to Control Salts     Maintain Irrigation Uniformity for uniform wetting and penetration Monitor soil moisture to track the depth of penetration Schedule irrigation to match crop needs Utilize storage to control irrigation rates and timing  Soil storage or lined pond storage  Monitor soil salinity

LAND TREATMENT SYSTEM PRACTICES  Manage Hydraulic and Oxygen Demand Load  Prevent prolonged water logged soils and oxygen demand overload  Anaerobic conditions promote mineral weathering  Creates more salts from soil minerals  Promotes excessive leaching.  Specific Practices to Control Potential for Mineral Weathering  Monitor oxygen demand load  Apply oxygen demand within capacity of soil system  Manage irrigation in dose and rest to prevent water logging  Sprinkler operated with short sets and mechanical move sprinklers  Light frequent applications that penetrate upper part of soil not full depth

LAND TREATMENT SYSTEM PRACTICES  Crop Selection  Crops must be tolerant of the salts concentrations and load  Use crops such as silage or hay to maximize biomass removal  Use multiple crops in a year to maximize removal  Maximize Acreage  Use as much of available acres as possible each year  Controls and spreads salts load across the site.  Make land treatment site as large as practical  More acreage reduces average salts load per acre  Blend with Fresh Water  Reduces concentrations and potential for crop damage  Reduces SAR to minimize need for calcium amendments that add salts  Larger acreages increase blending that occurs and reduces overall salts load.

POINTS OF COMPLIANCE  Ultimate point of compliance for land treatment systems is groundwater (WAC 173-200-060)  Upper most groundwater bearing zone  Throughout the site  Points of compliance may be based on perceived risk EC of discharge at 500 µmhos/cm over source (in California) Soil chloride concentration trend 4:1 dilution to reduce salinity Salts management plan to control process wastewater FDS to groundwater standard  Salts load equal to crop uptake      Compliance should be based on achievable standards and management practices

Conclusions  Land treatment beneficial reuse is an essential tool for food processors.  At least 30 facilities in Washington, supporting nearly 4,000 jobs  Reuse of process wastewater conserves scarce irrigation supplies and declining groundwater in some areas  TDS as the dissolved mineral fraction is an inherent part of the process wastewater  From natural as well as processing sources  Load from process wastewater exceeds crop uptake and accumulates in soil  Best practices include pollution prevention, soil monitoring, good irrigation practices, crop selection, and controlled leaching to minimize potential to contaminate groundwater.  Perspectives on compliance must consider appropriate best management practices

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