Water Quality Module 5B F2024 PDF

Module 5B: Water Quality [Nathanson and Schneider, Chapter 4] Public domain. Fit to Drink Ways that surface water and groundwater can become contaminated 2 Water Pollution – Sources and...

Module 5B: Water Quality [Nathanson and Schneider, Chapter 4] Public domain. Fit to Drink Ways that surface water and groundwater can become contaminated 2 Water Pollution – Sources and Categories Government regulations state that water pollution is any chemical, physical or biological change or form of energy that has a harmful effect on living organisms or that makes water unusable for desired use (such as drinking water source or recreational purposes). Point sources These sources are discharges from one easily identifiable location or source such as a sewer discharge pipe, a drain pipe from a roof, a drum storage area etc). These sources tend to be easier to contain and treat with pollution control equipment such as catch basins, filters, etc. In Canada, a discharge permit is required for all point sources Industrial Point Source Water Pollution. Films On Demand 3 Non-Point Sources These sources cannot be traced easily to one particular location but tend to be widespread. Examples are: runoff of fertilizer from agricultural lands around a lake; runoff of manure from farming operations; runoff and erosion from mining operations or construction. These tend to be more difficult to contain and treat. Non-Point Source Water Pollution: An Overview of Runoff. Films On Demand 4 Physical water-quality parameters Chemical water-quality parameters Biological water-quality parameters 6 Solids Suspended solids Dissolved solids Turbidity (a measure of suspended solids) Temperature Colour Taste Odour 7 Solids are present in water either as dissolved or as suspended solids Suspended solids (SS) are those that are retained by a glass fibre filter Dissolved solids (DS or TDS) are those that pass through the filter with water Total solids (TS). TS = SS+DS 8 Total solids (TS) test – measures all the solids, suspended and dissolved, organic and inorganic: Measured by evaporating sample at 105ºC±1ºC to a constant weight and weighing the residue Suspended solids (SS) test – measures solids that can be removed by filtration water is filtered and the residue is dried to a constant weight at 105ºC±1ºC Dissolved solids (DS or TDS) – the difference between the total solids and the suspended solids, mg/L If only TDS is required, water sample is filtered and the filtrate is placed into an oven at 105ºC±1ºC to allow water to evaporate to constant weight and weighing the residue. 9 120.0 mL of lake water sample was placed into an evaporating dish and placed into an oven at 105ºC±1ºC to allow evaporation of water to constant weight. Calculate TS concentration if the weight of evaporating dish with dry solids was 88.0965 g and the weight of empty evaporating dish was 88.0634 g 10 SS may consist of inorganic or organic particles or of immiscible liquids Inorganic SS: clay, silt, and other soil constituents Organic SS: plant fibers, algae cells, bacteria, etc. Domestic WW contains large quantities of mostly organic SS Immiscible liquids such as oils and greases are present in domestic and many industrial WW 11 100 mL of the wastewater sample is filtered. The filter with the solids is dried at 105ºC to a constant mass of 2.0168 g. Determine a suspended solids concentration if the dry mass of the filter is 2.0089 g. 12 Dissolved solids (DS) are those that pass through the filter with water DS may also consist of organic and/or inorganic compounds Examples of organic DS: _______________ Examples of inorganic DS: ______________  If the filtered portion of the water sample is placed into an oven at 105 ⁰C and water is evaporated, the solids remaining as a residue are called total dissolved solids (TDS) 13 Example: The weight of an evaporating dish is 81.3456 g. After a water sample is filtered, 100 mL of the filtrate is evaporated and the weight of the evaporating dish with the residue is determined to be 81.3675 g. Determine the TDS concentration. Water Quality 14 Heat Energy – lake water is commonly used to cool industrial processes and power plants. Hot water discharges come mostly from power plants Thermal pollution raises water temperature and lowers the DO level since solubility of oxygen reduces as temperature increase. Increase in temperature results in the increase of biological activity and, as a result, rapid consumption of oxygen by microorganisms Accelerated growth of algae usually occurs in warm water This leads to taste and odour problem Some fish cannot survive in the low oxygen environment 15 Pure water is colourless Colour can be caused by dissolved or suspended colloidal particles Apparent colour is caused, at least partly, by SS True colour – colour that remains after removal of SS Sources of colour; natural and anthropogenic: Leaves, tannins – yellowish-brown hues Tannins are polyphenolic compounds found in leaf, bud, seed, root, and stem tissues of plants Iron oxides- reddish Manganese oxides – brown or blackish Textile, dyeing, pulp and paper, food processing, slaughterhouse operations may colour 16 Sources: minerals, metals and salts from the soil, products of biological reactions, and constituents of WW. Common odourous compounds: H2S (rotten egg smell), amines, ammonia A panel of people is used to conduct odour and taste tests 17 Dissolved oxygen Organics (BOD and COD) Total dissolved solids Alkalinity Acidity Hardness Metals Oil and grease Nutrients 18 DO is one of the most important water parameters in surface water bodies Oxygen solubility highly depends on water temperature (see “Temperature” above) If organic material is present in water, microorganisms (first of all bacteria) will rapidly consume DO Trout and other sensitive fish will perish at low DO levels When the DO concentration is