Saturday, December 26, 2009

Tests Of Polluted Water


Color in water may result from the presence of natural metallic ions (iron and manganese),
humus and peat materials, plankton, weeds, and industrial wastes. Color is removed to make a
water suitable for general and industrial applications. Colored industrial wastewaters may require color removal before discharge into watercourses.

Due to biological treatment, if required, the temperature of wastewater should be kept between 10 and 30 C if possible. This is due to the optimum temperature that microorganisms function at.

Biochemical Oxygen demand (BOD): The strength of the wastewater is often determined by measuring the amount of oxygen consumed by microorganism like bacteria in biodegrading the organic matter. The measurement is known as the Biochemical Oxygen Demand (BOD).
Chemical Oxygen Demand (COD): This is a means of measuring the ability of wastewater to
sustain aquatic life, essential for the preservation of the environment. It also enables proper
assessment of treatment plant performance. Aquatic organisms and animals require dissolved
oxygen to flourish. The Chemical Oxygen Demand (COD) test gives an indication of the impact of
discharge waters on aquatic life by measuring the oxygen depleting nature of the discharge water.
Total suspended Solids (TSS): TSS is mainly organic in nature, are visible and can be removed from the wastewater by physical/ mechanical means e.g. screening and sedimentation. TSS is measured by filtering a certain quantity of effluent and then drying the filtrate at certain
temperature e.g. 1050C followed by weighing. TSS is expressed as parts per million or in
milligram/litre. The pore size of the filter paper is very important in estimating the TSS, the
nominal pore size 1.58 micro metre.
Total Dissolved Solids (TDS):TDS is the sum total of all of the dissolved things in a given body of water. It is everything in the water that's not actually water. It includes hardness, alkalinity, cyanuric acid, chlorides, bromides, sulfates, silicates, and all manner of organic compounds.TDS is
referred to as the total amount of mobile charged ions, including minerals, salts or metals
dissolved in a given volume of water, and is expressed in units of mg per unit volume of water
(mg/L), or as parts per million (ppm).

Microorganisms - Microscopic living objects, which require energy, carbon and small amounts of inorganic elements to grow and multiply. They get these requirements from the wastewater and the sun, and in doing so help to remove the pollutants.

pH – A term used to express the intensity of the acid or alkalinity source. pH represents the
effective concentration (activity) of hydrogen ions (H+) in water. This concentration could be
expressed in the same kind of units as other dissolved species, but H+ concentrations are much
smaller than other species in most waters. The activity of hydrogen ions can be expressed most
conveniently in logarithmic units. pH is defined as the negative logarithm of the activity of H+
pH = -log [H+]

Sludge-The settable solids separated from the liquid during sedimentation (clarification). The
sludge is very toxic in nature and needs to be dealt with very carefully. Under no circumstances it should be mix with the environment again.
A number of metals are listed in the national environmental quality standards for industrial wastewater, including Cd, Cr, Cu, Fe, Pb, Hg, Ni and Zn. Many metals, which are usually only available naturally in trace quantities in the environment, can be toxic to humans, plants, fish and other aquatic life.

Phosphorus, Total Nitrogen, Nitrate and Ammonia
These parameters are all used as a measure of the nutrients present in the wastewater, as a high nutrient content can result in excessive plant growth in receiving water bodies, subsequent oxygen removal and the death of aquatic life.
Sulphur and Sulphide
Textile dyeing uses large quantities of sodium sulphate and some other sulphur containing chemicals. Textile wastewaters will therefore contain various sulphur compounds and once in the environment sulphate is easily converted to sulphide when oxygen has been removed due to oxidation of BOD in the effluents. This is a problem because hydrogen sulphide can be formed which is a very poisonous gas, it also has an unpleasant smell of rotten eggs. The presence of sulphides in effluents can upset biological treatment processes.
Oil and Grease
This includes all oils, fats and waxes, such as kerosene and lubricating oils. Oil and grease causes unsightly films on open water bodies and negatively affects aquatic life. They can also interfere with biological treatment processes and cause maintenance problems as they coat the
surfaces of components of an ETP.

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