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Presentation about conductivity, TSS, TDS, VSS for an undergraduate environmental engineering lab.

Presentation about conductivity, TSS, TDS, VSS for an undergraduate environmental engineering lab.

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    4 lab-tss-tds-vss 4 lab-tss-tds-vss Document Transcript

    • 9/26/2013 1 Solids are categorized based on particle size and characterization as: – Total Suspended Solids (TSS) – Total Dissolved Solids (TDS) – Volatile Suspended Solids (VSS) – Total Solids (TS) TSS are the amount of filterable solids in a water sample. Samples are filtered through a glass fiber filter. The filters are dried and weighed to determine the amount of total suspended solids in mg/l of sample. TDS are those solids that pass through a filter with a pore size of 2.0 micron or smaller. They are said to be non-filterable. After filtration the filtrate (liquid) is dried and the remaining residue is weighed and calculated as mg/l of Total Dissolved Solids. VSS are those solids lost on ignition (heating to 550 degrees C.) They give a rough approximation of the amount of organic matter present in the solid fraction of wastewater, activated sludge and industrial wastes TS are the total of all solids in a water sample. They include the total suspended solids, total dissolved solids, and volatile suspended solids.
    • 9/26/2013 2 A water sample is filtered through a standard glass-fiber filter, and the filtrate liquid is evaporated to dryness in a weighed dish and dried to constant weight at 180°C. The increase in dish weight represents the total dissolved solids Apparatus – Glass-fiber filter disks – Membrane filter funnel – Gooch crucible, 25-mL to 40-mL capacity – Suction flask – Drying oven, for operation at 180 ± 2°C. Preparation of evaporating dish: If volatile solids are to be measured, ignite cleaned evaporating dish at 550°C for 1 h in a muffle furnace. If only total dissolved solids are to be measured, heat clean dish to 180 ± 2°C for 1 h in an oven. Store in desiccator until needed. Weigh immediately before use. Sample analysis: Stir sample with a magnetic stirrer and pipet a measured volume onto a glass-fiber filter with applied vacuum. Wash with three successive 10-mL volumes of reagent-grade water, allowing complete drainage between washings, and continue suction for about 3 min after filtration is complete. Transfer total filtrate (with washings) to a weighed evaporating dish and evaporate to dryness in a drying oven. Dry evaporated sample for at least 1 h in an oven at 180 ± 2°C, cool in a desiccator to balance temperature, and weigh. TDS [mg/L] = (A – B) X 1000 / (sample volume [mL]) A = weight of dried residue + dish, mg, and B = weight of dish, mg.
    • 9/26/2013 3 TDS and electrical conductivity are in a close connection. The more salts are dissolved in the water, the higher is the value of the electric conductivity The majority of solids, which remain in the water after filtration are dissolved ions. Sodium chloride for example is found in water as Na+ and Cl- High purity water is the ideal case only in H2O without salts or minerals and has a very low electrical conductivity Temperature affects conductivity so that its value increases from 2 up to 3 % per 1 degree Celsius. Conductivity is a measure of the ability of water to pass an electrical current. Conductivity in water is affected by the presence of inorganic dissolved solids such as chloride, nitrate, sulfate, and phosphate anions (ions that carry a negative charge) or sodium, magnesium, calcium, iron, and aluminum cations (ions that carry a positive charge). Organic compounds like oil, phenol, alcohol, and sugar do not conduct electrical current very well and therefore have a low conductivity when in water. Conductivity is also affected by temperature: the warmer the water, the higher the conductivity. For this reason, conductivity is reported as conductivity at 25 degrees Celsius (25° C). Reference: http://water.epa.gov/type/rsl/monitoring/vms59.cfm
    • 9/26/2013 4 Affected by geology. Streams that run through areas with granite bedrock tend to have lower conductivity because granite is composed of more inert materials that do not ionize (dissolve into ionic components) when washed into the water. On the other hand, streams that run through areas with clay soils tend to have higher conductivity because of the presence of materials that ionize when washed into the water. Ground water inflows can have the same effects depending on the bedrock they flow through. Discharges to streams can change the conductivity depending on their make-up. A failing sewage system would raise the conductivity because of the presence of chloride, phosphate, and nitrate; an oil spill would lower the conductivity. Conductivity meters are typically calibrated using a 0.01 N KCl solution, which has a specific conductance of 1413 µS at 25°C (conductivity of solutions increases with temp). Specific conductivity is commonly used in water analyses to rapidly estimate total dissolved solids (TDS) content: ~ 0.70
    • 9/26/2013 5 Reference: http://www.eutechinst.com/techtips/tech-tips40.htm
    • 9/26/2013 6 Water type Spec. Cond. (µS) TDS (mg/L) DI water 0.5 – 3.0 0.3 – 1.7 U.S. potable water 50 - 1500 30 – 850 Seawater 53,000 – 62,000 30,000 – 35,000 !!! "# $%& '(%) & * + Where A = weight of dried residue + dish (mg) B = weight of dish (mg)
    • 9/26/2013 7 TSS are solid materials, including organic and inorganic, that are suspended in the water. These would include silt, plankton and industrial wastes. High concentrations of suspended solids can lower water quality by absorbing light. Waters then become warmer and lessen the ability of the water to hold oxygen necessary for aquatic life. Because aquatic plants also receive less light, photosynthesis decreases and less oxygen is produced. Suspended solids can clog fish gills, reduce growth rates, decrease resistance to disease, and prevent egg and larval development. Particles that settle out can smother fish eggs and those of aquatic insects. The material that settles also fills the spaces between rocks and makes these microhabitats unsuitable for various aquatic insects, such as mayfly nymphs, stonefly nymphs and caddisfly larva. Suspended solids can result from erosion from urban runoff and agricultural land, industrial wastes, bank erosion, bottom feeders (such as carp), algae growth or wastewater discharges. A well-mixed sample is filtered through a standard GF/F glass fiber filter, and the residue retained on the filter is dried to constant weight at 103-105C Glass microfiber filters discs, 5.5 cm, without organic binder, Whatman type GF/F (0.7 Fm) Disposable aluminum dishes Tweezers Suction flask, 1000 mL 47 mm glass microanalysis filter holder (funnel, clamp, and base) Drying oven for operation at 103-105°C Muffle furnace for operation at 550 ± 50°C Desiccator Analytical balance, capable of weighing to 0.1 mg Reagent grade water (ASTM Type I water)
    • 9/26/2013 8 Insert the filter disk onto the base and clamp on funnel. While vacuum is applied, wash the disk with three successive 20 mL volumes of reagent grade water. Remove all traces of water by continuing to apply vacuum after water has passed through. Remove funnel from base and place filter in the aluminum dish and ignite in the muffle furnace at 550°C ± 50°C for 30 minutes. Rewash the filter with an additional three successive 20 mL volumes of reagent water, and dry in an oven at 103-105°C for one hour. When needed, remove dish from the oven, desiccate, and weigh. Select a sample volume (max. of 200 mL) that will yield no more than 200 mg of total suspended solids. Place the filter on the base and clamp on funnel and apply vacuum. Wet the filter with a small volume of lab grade water to seal the filter against the base. Shake the sample vigorously and quantitatively transfer the sample to the filter using a large orifice, volumetric pipet. Remove all traces of water by continuing to apply vacuum after sample has passed through. Rinse the pipet and funnel onto the filter with small volume of reagent grade water. Remove all traces of water by continuing to apply vacuum after water has passed through. Carefully remove the and filter from the base. Dry at least one hour at 103-105°C. Cool in a desiccator and weigh. Total Suspended Solids, mg/L = (A-B) x 1,000/C – Where: A = weight of filter and dish + residue in mg – B = weight of filter and dish in mg – C = volume of sample filtered in mL If volatile suspended solids is desired retain the sample in the dish for subsequent ignition at 550°C (see next slide).
    • 9/26/2013 9 After determining the final weight in the total suspended solids analysis, place the filter and dish in the muffle furnace and ignite at 550°C ± 50°C for 30 minutes. Allow to partially air cool, desiccate and weigh. Volatile Suspended Solids, mg/L = (A-B) x 1,000/C Where: A = weight of residue + filter and crucible in mg from TSS test Total Suspended Solids test B = weight of residue + filter and crucible in mg after ignition C = volume of sample filtered in mL TDS 442: A mixture of sodium sulfate (40%), sodium bicarbonate (40%) and sodium chloride (20%). The 442 mixture is designed to mimic the ions often present in natural fresh water systems.
    • 9/26/2013 10