KNOWING WATER QUALITY TEST PARAMETERSPutu Elvira Yulianthi, S.SiWater is one of the important natural resources in an ecosystem, where water is needed by living things to survive.Along with the changing times, there is a high increase in population from year to year and is accompanied by environmental problems, one of which is the problem of water pollution.According to PP No. 82 of 2001, water pollution is the entry of living things, substances, energy, or other components into water caused by human activities, so that water quality decreases to a certain level which causes water to not function according to its designation. .Industrialization and urbanization have had a significant impact on the environment.Disposal of industrial and domestic/household waste into water bodies is the main cause of water pollution.In general, there are two main sources of water pollution, namely water pollutant sources from fixed/immovable points (point sources) and water pollutant sources from non-fixed/moving points (non-point sources).Sources of pollution from fixed points include factories, septic tank systems, wastewater treatment facilities, and other sources that clearly discharge pollutants into water sources.Meanwhile, the sources of non-fixed pollutants are more difficult to identify because they cannot be traced back.Examples include sediment, fertilizers, chemicals and waste from animal farms, construction sites, and mines.This water pollution can be overcome by making various efforts and cooperation between the government and the community.One effort that can be done to overcome this problem is to measure water quality using test parameters such as temperature, pH, TSS, BOD, COD, and DO.The data obtained from the results of this water quality test can be used to determine the appropriate steps in overcoming the problem of water pollution.Temperature is usually measured using a mercury thermometer with a Celsius (oC) scale.The pH value of water is measured using a pH meter, where this measurement aims to express the condition of acidity (hydrogen ion concentration) in the water.The pH scale ranges from 1-14, where the range of pH values ​​of 1-7 includes acidic conditions, pH 7-14 includes alkaline conditions, and pH 7 is neutral conditions.Furthermore, suspended solids or TSS (Total Suspended Solid) is used to determine water density, process efficiency and unit process load.Generally TSS can be in the form of mud, clay, metal oxides, sulfides, algae, bacteria, and fungi.TSS can be removed by flocculation and filtration.TSS contributes to turbidity thereby limiting light penetration for photosynthesis and visibility in waters.BOD (Biological Oxygen Demand) or biological oxygen demand is the amount of oxygen needed by organisms in the water to break down (degradate / oxidize) organic waste materials in a water.The higher the BOD value, the higher the activity of aquatic organisms to decompose organic matter, so that high levels of BOD can reduce the amount of dissolved oxygen in waters.If the dissolved oxygen content of water decreases, the ability of anaerobic bacteria to break down organic waste also decreases.This causes an unpleasant odor in polluted waters.COD (Chemical Oxygen Demand) or chemical oxygen demand is the amount of oxygen needed so that the waste materials in a water can be oxidized through chemical reactions.In this test usually use Potassium bichromate (K2CrO7) as the oxygen source.The more potassium bichromate is needed, the more oxygen is needed.This indicates that a water tested the higher the level of pollution.DO (Dissolved Oxygen) or dissolved oxygen is needed by all living bodies for metabolic processes or the exchange of substances which then produce energy for growth and reproduction.With increasing depth of water, there will be a decrease in dissolved oxygen levels because the photosynthesis process is decreasing and the available oxygen levels are widely used for metabolic processes and the oxidation of organic and inorganic materials.Oxygen itself plays an important role as an indicator of the quality of a water, this is because dissolved oxygen plays a role in the oxidation and reduction of organic and inorganic materials.