Main parameters in the water quality discharge standards are briefly discussed in below:
pH
pH is a measure of the concentration of hydrogen ions in the waste water and gives an indication of how acid or alkaline the waste water is. This parameter is important because aquatic life such as most fish can only survive in a narrow pH range between roughly pH 6.5-8.
Oil and Grease
This includes all oils, fats and waxes, such as kerosene and lubricating oils. Oil and grease cause unpleasant films on open water bodies and negatively affect aquatic life. They can also interfere with biological treatment processes and cause maintenance problems as they coat the surfaces of components of ETPs.
BOD
Measurement of the oxidisable organic matter in waste water is usually achieved through determining the 5-day biological oxygen demand (BOD5), the chemical oxygen demand (COD) and total organic carbon (TOC).
pH is a measure of the concentration of hydrogen ions in the waste water and gives an indication of how acid or alkaline the waste water is. This parameter is important because aquatic life such as most fish can only survive in a narrow pH range between roughly pH 6.5-8.
Oil and Grease
This includes all oils, fats and waxes, such as kerosene and lubricating oils. Oil and grease cause unpleasant films on open water bodies and negatively affect aquatic life. They can also interfere with biological treatment processes and cause maintenance problems as they coat the surfaces of components of ETPs.
BOD
Measurement of the oxidisable organic matter in waste water is usually achieved through determining the 5-day biological oxygen demand (BOD5), the chemical oxygen demand (COD) and total organic carbon (TOC).
BOD is a measure of the quantity of dissolved oxygen used by microorganisms in the biochemical oxidation of the organic matter in the waste water over a 5-day period at 200C. The test has its limitations but it still used extensively and is useful for determining approximately how much oxygen will be removed from water by an effluent or how much may be require for treatment and is therefore important when estimating the size of the ETP needed.
COD
It oxidizes organic matter through a reaction with a mixture of chromic and sulfuric acid at high temperatures. COD is often used as a substitute for BOD as it only takes a few hours not five days to determine. COD is a measure of the oxygen equivalent of the organic material chemically oxidized in the reaction and is determined by adding dichromate in an acid solution of the waste water.
Color
It is an issue in dye house effluent because unlike other pollutants it is so visible. Reducing color is therefore important for the public perception of a factory. Consequently, international textile buyers are increasingly setting discharge standards for color. However, as a health and environmental issue color is less of a concern than many of the other parameters.
TDS and TSS
Waste water can be analyzed for total suspended solids (TSS) and total dissolved solids (TDS) after removal of coarse solids such as rags and grit. A sample of waste water is filtered through a standard filter and the mass of the residue is used to calculate TSS. Total solids (TS) is found by evaporating the water at a specified temperature. TDS is then calculated by subtracting TSS from TS.
Metals
A number of metals are listed in the national environmental quality standards for industrial waste water, including cadmium, chromium, copper, iron, lead, mercury, nickel and zinc. 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 waste water, as a high nutrient content can result in excessive plant growth in receiving water bodies, subsequent oxygen removal and the death of aquatic life.
Sulfur and Sulphide
Textile dyeing uses large quantities of sodium sulphate and some other sulphur containing chemicals. Textile waste waters will therefore contain various sulphur compounds and once in the environment sulphate is easily converted to sulphide when oxygen has been removed by the BOD of 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 interfere with biological treatment processes.
COD
It oxidizes organic matter through a reaction with a mixture of chromic and sulfuric acid at high temperatures. COD is often used as a substitute for BOD as it only takes a few hours not five days to determine. COD is a measure of the oxygen equivalent of the organic material chemically oxidized in the reaction and is determined by adding dichromate in an acid solution of the waste water.
Color
It is an issue in dye house effluent because unlike other pollutants it is so visible. Reducing color is therefore important for the public perception of a factory. Consequently, international textile buyers are increasingly setting discharge standards for color. However, as a health and environmental issue color is less of a concern than many of the other parameters.
TDS and TSS
Waste water can be analyzed for total suspended solids (TSS) and total dissolved solids (TDS) after removal of coarse solids such as rags and grit. A sample of waste water is filtered through a standard filter and the mass of the residue is used to calculate TSS. Total solids (TS) is found by evaporating the water at a specified temperature. TDS is then calculated by subtracting TSS from TS.
Metals
A number of metals are listed in the national environmental quality standards for industrial waste water, including cadmium, chromium, copper, iron, lead, mercury, nickel and zinc. 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 waste water, as a high nutrient content can result in excessive plant growth in receiving water bodies, subsequent oxygen removal and the death of aquatic life.
Sulfur and Sulphide
Textile dyeing uses large quantities of sodium sulphate and some other sulphur containing chemicals. Textile waste waters will therefore contain various sulphur compounds and once in the environment sulphate is easily converted to sulphide when oxygen has been removed by the BOD of 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 interfere with biological treatment processes.