Sewage pollution indicators

Articles

Wastewater pollution is caused by foreign substances that enter it and cause pollution and production of wastewater in a suspended or dissolved form. The higher the amount of these substances in the wastewater, the higher the pollution load. Therefore, measuring the amount of foreign matter in wastewater is the main key in determining the amount of pollution and pollution of wastewater. Here we will mention the most important indicators for measuring wastewater pollution.
Potential of Hydrogen
The power of an acid or base can be determined with the help of the potential of hydrogen (PH), which is expressed as a number. This index affects all living things, including humans, animals and plants, and its amount has very destructive effects on a variety of materials such as metals, building materials and living materials. Therefore, its determination and control has an important role in the health of the environment and people. Changes in pH upset the ecological balance of the aquatic environment and accelerate chemical interactions.
Chemical Oxygen Demand
The COD (Chemical Oxygen Demand) index is the oxygen required for chemical interaction, which refers to the amount of oxygen that is used chemically to oxidize organic matter in wastewater. In municipal wastewater, the COD to BOD ratio is usually a number close to 2, the higher the ratio, the higher the organic matter content, in which case the chemical treatment process will precede the biological treatment.
To determine the amount of foreign matter in wastewater, instead of measuring it directly, they calculate the amount of oxygen they need to oxidize, and the higher the amount of COD in wastewater, the greater the amount of foreign matter in it that causes pollution. will be. Since oxygen is the main cause of all chemical reactions, the higher the level of pollution and its indicators, the more oxygen is needed for oxidation.
Biochemical Oxygen Demand
BOD (Biochemical Oxygen Demand) refers to the amount of oxygen that must be supplied to aerobic bacteria so that they can decompose and stabilize organic matter in the wastewater that is biodegradable. BOD is the most important instrument for measuring degradable organic matter used in wastewater, and this indicator indicates the amount and severity of pollution, and the higher the amount, the more organic matter in the wastewater and the more difficult it will be to treat. The amount of this oxygen is expressed in milligrams per liter.
The difference between BOD and COD is that BOD represents an index of biodegradable organic matter, while COD is an index of all organic compounds present in wastewater, ie it also includes biodegradable organic matter, so COD values ​​are usually higher than BOD. Also, the most important advantage of this indicator compared to BOD is that it can be measured in one hour. However, if we want to use the BOD method, we have to wait for 5 days.
Total Suspended Solids
Total Suspended Solids (TSS) refers to the amount of suspended solids in wastewater that can usually be removed by gravity deposition. Suspended solids are divided into two groups: settable and non-settable solids. To measure the concentration of TSS, first the weight of the dried filter is weighed and then the water sample is filtered with it. The strainer is then dried and weighed at 103 to 105 ° C. The difference in filtration weight, before and after filtration, indicates the weight of the solids suspended in the water. If the TSS of wastewater is high, a sedimentation unit should be considered to remove these materials. The TSS of municipal wastewater is about 300 mg / l. The smaller the size of the filter pores, the more suspended solids remain on the filter.
Total Dissolved Solids
TDS (Total Dissolved Solids) index or total soluble solids used to measure the amount of soluble substances in wastewater. Soluble solids include anions and cations such as chloride, sulfate, sodium, potassium, and nitrate. Measurement of this factor does not play a major role in determining the quality of wastewater and can not be considered the main criterion for determining water quality, but often determines the degree of water transparency and knowing the amount of TDS, can also be used in reuse of wastewater for agricultural purposes. Because some plants are sensitive to its high content in water and soil.