Water Quality Parameters and Indicators

Water Quality Parameters and Indicators

            Water quality determines the ‘goodness’ of water for particular purposes. Water quality tests will give information about the health of the waterway. By testing water over a period of time, the changes in the quality of the water can be seen.  The water quality parameters are discussed below.

• Temperature: Temperature can exert great control over aquatic communities.  If the overall water body temperature of a system is altered, an aquatic  community shift can be expected. In water above 30⁰C, a suppression of all benthic organisms can be expected.Also, different plankton groups will flourish under different temperatures. For example, diatoms dominate at 20-25⁰C, green algae dominate at 30-35⁰C, and cyano-bacteria dominate above 35⁰C.
• pH value: pH is an indicator of the existence of biological life as most of them thrive in a quite narrow and critical pH range.
• Dissolved Oxygen (DO): DO is essential for aquatic life. A low DO (less than 2mg/l) would  indicate poor  water quality and thus would have difficulty in sustaining many sensitive aquatic life.
• Colour (Hazen): Colour is vital as most water users, be it domestic or industrial, usually prefer colourless water.  Determination of colour can help in estimated costs related to discolouration of the water.
• Conductivity: Conductivity indicates the presence of  ions within  the water, usually due to  in majority,  saline water and in part,  leaching.  It can also indicate industrial discharges. The removal of vegetation and conversion into monoculture may cause run-off to flow out immediate thus decrease recharge during drier period.  Hence, saline intrusion may go upstream and this can be indicated by higher conductivity.  
• Turbidity (NTU): Turbidity may be due to organic and/or inorganic constituents. Organic particulates may harbour microorganisms.  Thus, turbid conditions may increase the possibility for waterborne disease.  Nonetheless, inorganic constituents have no notable health effects. The series of turbidity-induced changes that can occur in a water body may change the composition of an  aquatic community. First, turbidity due to a large volume of suspended sediment will reduce light penetration, thereby suppressing photosynthetic activity of phytoplankton,  algae, and macrophytes, especially those farther from the surface. If turbidity is largely due to algae, light will not penetrate very far  into  the water, and primary production will be limited to the uppermost layers of water. Cyanobacteria (blue-green algae) are favoured  in this situation because they possess flotation mechanisms. Overall, excess turbidity leads to fewer photosynthetic organisms available to serve as food sources for many invertebrates. As a result, overall invertebrate numbers may also decline, which may then lead to a fish population decline.  If turbidity is largely due to organic particles, dissolved oxygen depletion may occur in the water body. The excess nutrients available will encourage microbial breakdown, a process that requires dissolved oxygen. In addition, excess nutrients may result in algal growth. Although photosynthetic by day, algae respire at night, using valuable dissolved oxygen. Fish kills often result from extensive oxygen depletion.
• Salinity: High salinity may interfere with the growth of aquatic vegetation. Salt may decrease the osmotic pressure, causing water to flow out of the plant to achieve equilibrium. Less water can be absorbed by the plant, causing stunted growth and reduced yields. High salt concentrations may cause leaf tip and marginal leaf burn, bleaching, or defoliation.   As per conductivity, salinity (NaCl content, g/kg) can be used to check for possible saline intrusion in future.
• Total Suspended Solids (TSS): Total Suspended  Solids is an indication of the amount of erosion that took place nearby or upstream. This parameter would be the most significant measurement as it would depict the effective and compliance of control measures e.g. riparian reserve along the waterways. The series of sediment-induced changes that can occur in a water body may change the composition  of an aquatic community. To measure total suspended and dissolved solids, a sample of water is placed in a drying oven to evaporate the water, leaving the solids. To measure dissolved solids, the sample is filtered before it is dried and weighed. To calculate the suspended solids, the weight of the dissolved solids is subtracted from the total solids.
• Total Dissolved Solids(TDS): The total dissolved solids (TDS) in water consist of inorganic salts and dissolved materials. In natural waters, salts are chemical  compounds comprised of anions such  as  carbonates,  chlorides, sulphates, and nitrates (primarily  in ground water), and  cations  such as potassium (K), magnesium (Mg), calcium (Ca), and  sodium (Na). In ambient conditions, these compounds are present in proportions that create a balanced solution. If there are additional inputs of dissolved solids to the system, the balance is altered and detrimental effects may be seen. Inputs  include bothnatural and anthropogenic source.
• Biochemical Oxygen Demand (BOD):  BOD is a measure of organic pollution to both waste and surface water. High BOD is an indication of poor water quality. 
• Chemical Oxygen Demand (COD): COD is an indicator of organics in the water, usually used in conjunction with BOD. High organic inputs trigger deoxygenation. If excess organics are introduced to the system, there is potential for complete depletion of dissolved oxygen. Without oxygen, the entire aquatic community is threatened. The only organisms present will be air- breathing insects and anaerobic bacteria. If all oxygen is depleted, aerobic decomposition ceases and further organic breakdown is accomplished anaerobically. Anaerobic microbes obtain energy from oxygen bound to other molecules such as sulphate compounds. Thus, anoxic conditions result in the mobilization of many insoluble compounds. In areas of high organics there is frequently evidence of rapid sewage fungus colonization. The various effects of the sewage fungus masses  include silt and  detritus entrapment, the smothering of aquatic macrophytes, and a  decrease in water flow velocities. An accumulation of sediment allows  a shift in the aquatic  system structure as colonization by silt-loving organisms occur.
• Ammoniacal Nitrogen: Ammonia  levels in  excess of the recommended limits may  harm  aquatic life.  Although the ammonia molecule is a nutrient required for life, excess ammonia may accumulate in the organism and cause alteration of metabolism or increases in body pH.  It is an indicator of pollution from the excessive  usage of ammonia rich fertilisers.
• Potassium: Potassium is macro nutrient  element  for plant growth.  It can occur naturally in minerals and from soils. High levels in surface water, especially in areas where there are agricultural activities as indicative of introduction of K due to application of fertilisers.
• Nitrate Nitrogen: The growth of macrophytes and phytoplankton is stimulated principally by nutrients such  as  nitrates. Many bodies of freshwater  are currently experiencing influxes of nitrogen and  phosphorus from outside  sources.  The increasing concentration of available phosphorus allows plants to assimilate more nitrogen before the phosphorus is depleted. Thus, if sufficient phosphorus is available, high concentrations of nitrates will lead to phytoplankton (algae) and microphyte (aquatic plant) production. This is mostly due to the usage of fertilisers.
• Total Coliform Count and Faecal Coliform Count:  Microbiological test  is  to detect  the level  of pollutions caused by living thing especially human who live or work in the area especially upstream of the site. These tests are based on  coliform bacteria as the indicator  organism.  The presence of these indicative organisms is evidence that the water has been polluted with faeces of humans or other warm-blooded animals.
• Pesticides (Chlorinated, Glyphosphate, Paraquat, Methamidaphos): These parameters are common tests for the level of agrochemical pollution.  Since a specific type of agrochemical to use is unknown at this stage, it is unknown at this stage the type of agrochemical that would be used in the proposed development, a range of test is recommended for analysing to  gauge  the existing condition  that could be used as baseline information or reference.
• Alkalinity: The Alkalinity or the buffering capacity of a stream refers to how well it can neutralize acidic pollution and resist changes in pH. Alkalinity measures the amount of alkaline compounds in the water, such as carbonates, bicarbonates and hydroxides.These compounds are natural buffers that can remove excess hydrogen (H+) ions.
• Hardness:  Hardness is frequently used as an assessment of the quality of water supplies. The hardness of a water is governed by the content of calcium and magnesium salts (temporary hardness), largely combined with bicarbonate and carbonate and with sulfates, chlorides, and other anions of mineral acids (permanent hardness).
• Metals: The effects of metals in water and wastewater range from beneficial through troublesome to dangerously toxic. Some metals are essential; others may adversely affect water consumers, wastewater treatment systems, and receiving waters. Some metals may be either beneficial or toxic, depending on concentration. The primary mechanism for toxicity to organisms that live in the water column is by absorption to or uptake across the gills: this physiological process requires metal to be in a dissolved form. This is not to say that particulate metal is nontoxic, only that particulate metal appears to exhibit substantially less toxicity than does dissolved metal. Not all metals are acutely toxic in small concentrations. The "heavy metals" include Copper (Cu),Iiron (Fe), Cadmium (Cd), Zinc (Zn), Mercury (Hg), and Lead (Pb) and are the most toxic to aquatic organisms. Some water quality characteristics which affect metal toxicity include temperature, pH, hardness, alkalinity, suspended solids, redox potential and dissolved organic carbon. Metals can bind to many organic and inorganic compounds which reduces the toxicity of the metal.
• Phosphorus:  Phosphorus is often the limiting nutrient for plant growth, meaning it is in short supply relative to nitrogen. Phosphorus usually occurs in nature as phosphate, which is a phosphorous atom combined with four oxygen atoms. Phosphate that is bound to plant or animal tissue is known as organic phosphate. Phosphate that is not associated with organic material is known as inorganic phosphate. Both forms are present in aquatic systems and may be either dissolved in water or suspended (attached to particles in the water column). Inorganic phosphate is often referred to as orthophosphate or reactive phosphorous. It is the form most readily available to plants and thus may be the most useful indicator of immediate potential problems with excessive plant and algal growth.