Determination Of The Chemical Oxygen Demand (Cod) Of River Water Samples

2907 words - 12 pages

IntroductionThe chemical oxygen demand (COD) is a measure of the amount of oxygen consumed by the organic material within a water sample that is oxidized by a strong chemical oxidant, such as potassium dichromate (K2Cr2O7). Its main use is as an indicator of the organic and inorganic matter within water and effluent discharge giving a quantitative value of water quality. There are other tests that are also used to measure the organic content of a water body, such as the biological oxygen demand test. The biological oxygen demand (BOD) and can be found by collecting a sample from the watercourse and incubating it at 200C for five days, and calculating the oxygen used over the incubation period (Harrison 1996). The COD is often used when other methods are not as effective to be used. One advantage of the COD test over other tests, such as the BOD test is that it is relatively fast to carry out, for example the BOD test takes place over a five-day incubation period whilst the COD tests can be carried out in 2 hours; hence provides a much quicker indication of water quality. This property of the test has resulted in a wide range of usage when monitoring and controlling the organic content of industrial waste from effluent systems and the receiving water bodies.Dichromate is often used as the oxidizing agent when determining the COD due to its ability to oxidise most materials and ease of manipulation (Chapman 1996). Test allows the organic matter within a sample to reduce the dichromate; any remaining dichromate is titrated with ferrous ammonium sulphate, FeSO4.(NH4)2SO4, where the Fe2+ ions are oxidised to Fe3+ by the remaining dichromate ions, Cr2O72-. The dichromate (Cr2O72-) is dissolved into a salt by the addition of sulphuric acid (Na2Cr2O7), this produces the strong oxidising agent.The half reaction for the dichromate ion oxidising the organic matter is (Harrison 1996): Cr2O72- + 14H+ + 6e 2 Cr3+ + 7H2OWhile the overall reaction if the organic matter was glucose is: C6H12O6 + Cr2O72- + 32H+ 6CO2 + 8Cr3+ + 22H2OThe COD test however does not identify the actual type of organic material or distinguish between the mixes of organic or inorganic material in the sample. It also cannot be used as a measure of the total amount organic matter in a water body as not every organic substance can be oxidised in this manor whilst some inorganic matter is oxidised. Common organic materials that are not effectively oxidised in the dichromate solution include straight chain aliphatic compounds, aromatic hydrocarbons, pyridine and some acetic acids (Ballance 1996). The addition of a catalyst can aid the oxidation of the straight chain compounds, however the catalysts, such as silver sulphate, can react with other elements in the water samples, for example chlorides, bromides or iodides, producing partly oxidised precipitants.Problems in sampling can arise as many containers release organic substances into...

Find Another Essay On Determination of the Chemical Oxygen Demand (COD) of River Water Samples

Determination of Bulk Density and Water Content of a Cohesive Soil

883 words - 4 pages ObjectiveThe objective of this experiment is to determine the bulk density and water content of a wet, cohesive soil.IntroductionThe bulk density of a soil is simply the total mass per total volume. This means the soil sample is weighed with the water still in the sample and then divided by the total volume it occupies giving the bulk density. Finding out the bulk density of a soil is important as it can reveal how much total dry material you

Analysis of the Oxygen Group on the Periodic Table

2223 words - 9 pages . We need it to survive, and it starts many chemical reactions. When oxygen is alone, it usually is in pairs (O2). (“Davis, UCA”) We need it to have any of our life on earth. It combines with two hydrogens to form water (H2O). We breathe it in as O2, but then we release it as carbon dioxide or CO2 for plants to absorb and have nutrients. It changes our world every day. Oxygen is mostly found as a gas at room temperature. (“Davis, UCA”) When

Discussion on the Determination of Self

1141 words - 5 pages Discussion on the Determination of Self In every day life we experience causality and order, which would suggest that everything is ordered and caused by something outside ourselves. However it is hard to believe that we have no free choices when presented with a decision to be made, surely if we were unable to make choices concerning the direction and outcome of his own life, is a slave. However many philosophers and

The Biological and Chemical Effects of Organic and Chemical Fertilizers

1693 words - 7 pages available to the plant upon fertilization. In the laboratory where the fertilizer is made, nutrients have already undergone any chemical changes needed so that the plant can absorb it. Nutrients are measured exactly in inorganic fertilizers. Excess nutrients can cause health problems with the plants, and too small of an amount would be ineffective. Unfortunately, chemical fertilizers are also easily washed away by rain water, or, if too close to

Adaptations of the Placenta and Foetus to Improve Oxygen Availability

1278 words - 5 pages form of oxygen, glucose and other substances whilst excreting waste products such as carbon dioxide. The placenta and foetus feature many adaptations to ensure the most efficient gas exchange and to ensure high oxygen availability to the foetus . Gas exchange across the placental blood-blood barrier is dependent on many factors such as interhaemal barrier thickness, the surface area of exchange and the concentration gradient of the gases, among

History of the Colorado River

1552 words - 6 pages it, and management efforts to curtail conflicts between vying interests over a shared water source. Figure 1. Map of the Colorado River THE COLORADO RIVER The Colorado River is located in the southwestern United States and northwestern Mexico. It is 1,450 miles long with its headwaters in the Rocky Mountain National Park in Estes Park, Colorado. Geologically, the Colorado River begins near Moab, Utah, at the junction of the Green

Determination of Body Composition

1728 words - 7 pages aim of this study coursework was determination of body composition using simple anthropometric techniques as measurements of height and weight, waist and hip, skinfold thickness; Bio-electric Impedance Analysis (BIA) and creatinine estimation of 24 hr urine collection and hence, to introduce the skills required to determine body composition from those measurements. Such measurements were used to estimate individual’s body fat mass (FM

Determination of HDI

1875 words - 8 pages Determination of HDI The HDI is one of many methods of determining human development, first introduced by the United Nations Program. It does not only focus on a country's economic wealth instead it looks at social, cultural and welfare criteria in a order to determine a country's quality of life. HDI is calculated by using three factors chosen by the UN. These can be seen below: 1. Average life expectancy

Letter Of Determination

740 words - 3 pages Letters of Determination, Devotion and Hope from the Frontier The authors of the document I chose are Charles and Nellie Wooster, a husband and wife who chose to make a new life in the western prairie, settling in Nebraska. This document contains letters written between the couple before Nellie joined Charles in their new home. These letters are an example of life on the new frontier and the hardships these settlers faced, such as

Self Determination of Guam

2512 words - 10 pages Self Determination of Guam I. Introduction Government is the institution through which a society makes and enforces its public policies. Throughout the relatively brief history of Guam, the indigenous people have never had the opportunity to determine their political status or decide democratically which type of governmental system to implement. Since the island's earliest days the original inhabitants always had to endure whatever

Matriarchs of the River Ki

1156 words - 5 pages The three prominent relationships in The River Ki are all very different due to the different times and people, but all of them have one thing in common--Hana. She is the stronghold throughout the book, not just because she is the main character, but because of her inordinate strength and spirit. She got much of the spirit from her grandmother, Toyono, who raised her after the death of her mother, Mio.Toyono was a prominent figure in Hana's life

Similar Essays

Lab Report Using A Chemical Titration To Measure Rate Of Conversion Of Hydrogen Peroxide To Water And Oxygen

2711 words - 11 pages Lab Report Using a Chemical Titration to Measure Rate of Conversion of Hydrogen Peroxide to Water and Oxygen Overview: In this laboratory you will use a chemical titration to measure and then calculate the rate of conversion of hydrogen peroxide (HO) to water and oxygen using the enzyme catalase. Objectives: Before doing this exercise, you should understand: Ø the general functions and activities of enzymes Ø the relationship between

Determination Of Available Phosphate In Water Spectrophotometric Procedure

5536 words - 22 pages range of concentration is generally associated with domestic raw sewages and its water quality index is low: 2. Thus, this river could be located near a domestic or industrial runoff, or the sample taken was close to a runoff. In any case, this water is considered unsafe for living organisms, as depletion in oxygen would be unavoidable, and highly contaminated.Despite the fact that each group studied the same river and lake samples, the sample itself

Myocardial Ischemia: The Lack Of Oxygen

2113 words - 8 pages Angina is chest pain which results from inadequate oxygen flow to the myocardium. If the demand for myocardial oxygen surpasses the ability of the coronary arteries to provide the heart with oxygen, myocardial ischemia happens. Angina is the clinical manifestation of reversible myocardial ischemia caused by either an increased demand for oxygen or a decreased supply of oxygen that can lead to myocardial ischemia (Lewis et al., 2010). Angina is

Power Shift In Water Governance Of Transboundary River Basins

3307 words - 13 pages 1. Introduction Nile, the longest river in the World, with two sources the White Nile and the Blue Nile is shared by eleven riparian countries (K. Paisley & Henshaw, 2013). The basin is characterized by higher seasonal fluctuation in its water flow, water quality degradation, water scarcity and rapid population growth (Brunnee & Toope, 2002). The majority of the water comes from the Ethiopian high lands (86%) and the rest of 14% comes from the