DISSOLVED OXYGEN MEASUREMENT (DO)

I. INTRODUCTION

1.1 Background

It is undeniable that water is the most important substance in life. Covering 70% of the Earth's surface is divided into two main categories, namely freshwater ecosystems and marine water ecosystems. Of the two aquatic systems sea water has the largest part that is more than 97%, the rest is fresh water is very important for humans for their life activities. Indonesi is an area with an area of ​​5.8 million km2 (territorial sea and ZEEI) and has many freshwater ecosystems of lakes, rivers, swamps, and reservoirs indispensable for. Aquatic ecosystems are indispensable to the life of the organism. The role of water for life increases with the advancement of human culture. If the water is used by the organism for its purposes, for example fish, the water quality must be in accordance with the water required by the fish.

Water quality generally indicates the quality or condition of water associated with a particular activity or necessity. Thus water quality will vary from activity to activity, for example water quality for irrigation purposes is different from water quality for drinking water. Water quality in terms of water quality analysis includes physical, chemical, and biological conditions that can affect water availability for human life, agriculture, industry, recreation and other water uses. Various sources of water used for life and livelihoods can be polluted by various sources pollution. Waste from living things, such as humans, animals, and plants may contribute to the contamination that will be used, both for the purposes of living beings and for other purposes of life. The presence of Toxic substances or the content of excessive organic matter will cause a disruption to the quality water. This situation will cause the oxygen in the water is in a critical condition, or damage the chemical level of water. Damage to the water chemistry will affect the function of water.

II. LITERATURE REVIEW

2.1 Understanding DO

Dissolved oxygen (abbreviated DO) or often also called oxygen demand (Oxygen demand) is one of the important parameters in water quality analysis. The value of DO usually measured in the form of this concentration indicates the amount of oxygen (O2), which is available in a body of water. The greater the DO value on water, indicating the water is of good quality. Conversely, if the DO value is low, it can be seen that the water has been contaminated. Measurements DO also aims to see the extent to which the body of water is able to accommodate water biota such as fish and microorganisms. In addition, the ability to clean water pollution is also determined by the amount of oxygen in the water. Therefore, the measurement of this parameter is highly recommended in addition to other frequently used parameters such as BOD and COD in a waters (Hutabarat and Evans, 2006: 67).

Salmin (2005) states Dissolved Oxygen (DO) is an important parameter in determining the quality of waters. DO plays a role in the oxidation and reduction processes of organic and inorganic materials, as it is known that DO is required by all living bodies for respiration, metabolic processes or the exchange of substances which then produce energy for growth and culture. Dissolved Oxygen is a basic need of plants and animals in water. Dissolved oxygen can be derived from the photosynthetic process of aquatic plants and air entering into water at a limited speed and is represented in units of ppm (part per million). Dissolved Oxygen (DO) is required by all living organisms for respiration, metabolic processes or energy for growth and breeding. In addition, DO is also required for the oxidation of organic and inorganic materials in aerobic processes. Under aerobic conditions, the role of oxygen is to oxidize organic and inorganic materials with the end result being nutrients that can provide aquatic fertility. Under anaerobic conditions, the resulting oxygen reduces the chemical compounds to be simpler in the form of nutrients and gases.

2.2 Work Methods DO

Dissolved oxygen sensors (also known as DO sensors) are used as terms or expressions of the process of measuring the amount of dissolved oxygen concentration in unit water volume units. The accuracy of data on the amount of dissolved oxygen concentration in water is essential and important in knowing the changes caused by natural phenomena and human activities. While the source of dissolved oxygen in this water is the atmospheric reaction as well as photosynthetic activity of aquatic plants (A. Manz, 2010).

DO or dissolved oxygen content represents the oxygen content in the water. The ability of water in dissolving oxygen is highly dependent on water temperature, oxygen gas pressure and water purity. Treatment of oxygen delivery through the respiratory tract (inhaled through the nose) Section per million. It is a very small number of units. 1ppm = 1 part / 1,000,000 so water containing oxygen 80ppm = 80 milligrams of oxygen in 1 liter of water (Gulliver, 2010).

Is a very effective method to make drinking water. This process can reduce the amount of organic, inorganic, bacterial and water-contaminated particles. The reverse osmosis process is based on an osmotic process involving selective water movement from one side to the other on the membrane. Pressure is given to push water across the membrane, while the contaminant can not pass through the membrane so that more pure water is gathered on one side (Sidabutar, 2009).

2.3 Factors Affecting DO

Oxygen levels in seawater will increase with lower temperatures and decrease with increasing salinity. In the surface layer, oxygen levels will be higher, because of the diffusion process between water with free air and the process of photosynthesis. With increasing depth there will be a decrease in dissolved oxygen levels, as the photosynthesis process decreases and oxygen levels are widely used for respiration and oxidation of organic and inorganic materials The organism's need for oxygen varies considerably depending on type, stage and activity. Oxygen needs for fish in a state of silence is relatively less when compared with fish at the time of moving or spawning. Certain types of fish that can use oxygen from free air have more resistance to water dissolved oxygen (Nontji, 2002: 93).

According to Mills in Effendi (2003), Earth's atmosphere contains about 210 ml / liter of oxygen. Oxygen is one of the gases dissolved in the waters. The dissolved oxygen content in natural waters varies, depending on temperature, salinity, water turbulence, and atmospheric pressure. The greater the temperature and altitude as well as the smaller the atmospheric pressure, the less dissolved oxygen content.

2.4 Sources of DO in waters

The dissolved oxygen contained in water, derived from the air and the result of photosynthetic process of water plants. Oxygen is required by all creatures that live in water such as fish, shrimp, shellfish and other animals including microorganisms such as bacteria. Dissolved Oxygen (DO) is required by all living organisms, these are some of the benefits, for breathing, metabolic processes or the exchange of substances which then produce energy for growth and culture, oxygen is also required for the oxidation of organic and inorganic materials in aerobic processes primary oxygen in a waters comes from a diffusion process of free air, the result of photosynthesis of living organisms (Mulyanto, 2009: 2).

Oxygen levels in seawater will increase with lower temperatures and decrease with increasing salinity. In the surface layer, oxygen levels will be higher, because of the diffusion process between water with free air and the process of photosynthesis. With increasing depth there will be a decrease in dissolved oxygen levels, as the photosynthesis process decreases and oxygen levels are widely used for respiration and oxidation of organic and inorganic materials The organism's need for oxygen varies considerably depending on type, stage and activity. Oxygen needs for fish in a state of silence is relatively less when compared with fish at the time of moving or spawning. Certain types of fish that can use oxygen from free air have more resistance to water dissolved oxygen (Nontji, 2002: 93).

2.5 Role of O2 Watered

As it is known that oxygen acts as an oxidizing and reducing toxic chemicals into other, simpler, non-toxic compounds. In addition, oxygen is also needed by microorganisms for breathing. Certain organisms, such as microorganisms, play a very important role in decomposing toxic chemicals into other, more simple and non-toxic compounds. Because of this important role, industrial effluents and waste before disposing into the general environment are first enriched in oxygen levels. The speed of oxygen diffusion from air, depends on several factors, such as turbidity of water, temperature, salinity, mass movement, water and air such as currents, waves and tides (James, 2003).

2.6 O2 relationship with parameters

The amount of oxygen needed by aquatic organisms depends on the species, size, amount of feed eaten, activity, temperature, and so on. Low oxygen concentrations can cause anorexia, stress, and death in fish. If in a pool of dissolved oxygen content equal to or greater than 5 mg / l, then the process of reproduction and growth of fish will run well. In waters containing detergent, the oxygen supply from the air will be so slow that the oxygen in the water is very small. Dissolved oxygen is the amount of oxygen in milligrams contained in one liter of water (ppt). Dissolved oxygen generally comes from air diffusion through the water surface, inlet flow, rain water, and the result of photosynthetic process of plankton or water plants (Hutabarat and Evans, 2006: 67).

Low O2 in water causes fish or aquatic animals to pump large amounts of CO2 into their respirator to take O2 contained in water. Low O2 can prevent fish from using the surface respirator because it can alter the osmuregulation that has been prepared (Basraeyi, 2010).