- Published: October 31, 2021
- Updated: October 31, 2021
- University / College: Carleton University
- Language: English
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According to Mohapatra (488), coliform is a general term used to refer to Gram-negative, rod-shaped facultative anaerobic bacteria. These coliforms are identified by production of a gas from glucose or other sugars. In addition, the fermentation of lactose acid and production of a gas within 48 hours at 35 degrees Celsius is also another identification criterion that is used. Species that fall under the coliform group include Citrobacter, Escherichia (E.coli), Klebsiella and Entrobacter (Mohapatra 488).
Fecal coliform bacteria normally thrive in the intestinal tract of humans and other warm-blooded animals. Hagedorn, Blanch, and Harwood (454), classify fecal coliforms asa group of coliforms that thrive in high temperatures of about 44.5 degrees Celsius. These fecal coliforms are non-disease causing organisms. Their ability to grow in mediums at this temperature is the main distinguishing characteristic from other coliform types (Laws 188). The main species contained in this group are the E.coli and the Klebsiella. The Klebsiella rarely occurs in human feces (Laws 188). The E.coli is regarded as an indicator of fecal pollution rather than fecal coliforms. In the United States, E.coli is the recommended standard indicator used in freshwater beaches (Laws 188). Their existence in surface water bodies indicates the occurrence of a human being or animal waste in the water. Some of the sources of E.coli sanitary sewer overflow especially when it rains. The excess overflow is released to nearby waterways. In addition, leaking septic systems leak sewage, which contains E.coli into the nearby surface lakes. Moreover, wildlife such as ducks and geese that live nearby lakes tend to contaminate the water. Number of fecal coliform bacteria gives a clear indication of the level of pollution present in the surface or lake waters. If the water body contains low amounts of fecal coliforms, it indicates that the amounts of disease-causing organisms are minimal.
Why is Coliform a Good near shore Indicator
Coliforms are good shore indicator due since they provide a workable index of sanitary water quality (National Research Council 126). Swimming in lake waters with an average coliform content of 2300 per 100 milliliters has been found to cause a significant increase in illnesses (Salvato, Leonard, and Agardy 1188). A change in the levels of total coliforms in drinking water by more than 10 percent of the sampling sites should be noted. This gives an indication in the changes of water quality that requires necessary actions to be implemented.
Methodology for sampling and monitoring of coliform in surface water/lake
Levels of fecal coliforms in surface waters vary depending on the weather conditions. Before sampling process begins, it is necessary to ensure the correct sample container is selected. In addition, the sample container needs to be sterilized before use. EPA recommends the use of Pyrex glass or plastic containers (Environmental Protection Agency 1). In case, the containers are to be used, sterilization is required. Basic procedure for collecting a representative sample requires the sample bottle to remain closed after sterilization until when the sample is collected. Consequently, when opening the sample bottle, the bottle stopper and cap should be removed as one unit and the cap should not be touched to avoid contamination. When submerging the sample in water using hands, the bottle should be held against the current. The sample bottle is filled to about three-quarters full. The remaining space allows the sample to be mixed by shaking before further analyses. The stopper is replaced back, and details such as date of sampling, time, and location of sapling are recorded in the sampling tag.
Quality assurance/quality control procedures in the collecting samples are also necessary when collecting the regular samples. A sample collected at the similar location and time via the same sampler, or a different one is referred to as a field duplicate. Collection of internal field duplicates is carried out at 10 percent of the sampling sites alongside the normal samples. This sample will be labeled with a different labeling style that has the notation D to indicate it is a field duplicate. To ensure precision for the normal samples and field duplicates, lab analysis of the fecal coliforms is done per 100 milliliters fro samples gathered at the same site.
A trained sampler gathers an external field duplicate independently. In addition, the independent sampler performs the analysis. This independent sampler is a trained person or a team of skilled individuals. The purpose of collecting these external field duplicates is to conduct a laboratory precision analysis and estimates the sampling.
Another sampling procedure applied in quality assurance/quality control of coliforms is the use of field blanks. As is the internal field duplicates, the field blanks are collected at 10 percent of the samples sites together with the normal samples. The sterile sampling containers are filled with sterile water during sampling. This is done at the sampling sites. The purpose of field blanks is to recognize contamination of the samples or errors.
Importance of Quality Assurance/Quality Control
Quality assurance refers to an arrangement of activities that are designed to make sure the water quality data meets the prescribed standards of quality in the sampling program. In addition, it involves training, documentation, planning, and constancy in the collection of samples, analyses, reporting, and validation of the samples. Quality assurance at the planning stage predicts problems that are likely to occur during sampling. Quality control is used to describe the technical measures used to decrease errors that may arise in the sampling program. In addition, quality control is used to act in response to observed problems in the sampling and monitoring methodologies. Furthermore, most decisions during the monitoring stage are dependent on the technical measures that are applied depending on the pre-specified standard of quality.
Quality control allows evaluation accuracy, precision, completeness, sensitivity, representativeness, and comparability of the sampling data. Precision refers to the degree of similarity between two subsamples split from the same sample. This allows the precision of the entire process to be estimated. Use of incoherent field techniques will result to imprecision. Increasing the number of samples increases the precision of the sampling process. Accuracy is determined using standard reference material of known value. However, fecal coliforms lack a standard referencing material. Representativeness gives an insight as to how well the sampling site is a depiction of the entire water body. Comparability allows two different data sets from the same water body to be compared. Sensitivity allows the discrimination between the capabilities of a method or procedure in responding to different levels of measurement of variables. Completeness provides the measure of the amount of data required for the sampling program.
Importance of Data Management System
The key function of data management activities is to ensure that there is a simple access to the collected data and related information (National Research Council 85). Data management involves the path of water quality data from the field and laboratory to its final use and storage. During these processes, errors are likely to arise. Furthermore, since the amount of data collected by the monitoring programs is large and the complex, computer assisted data management system is crucial in data management.
When selecting the appropriate data management system to use a number of factors are taken into account. These include the long-term use of the data, volume of data, existing data management capabilities, and quality assurance/quality control requirements. The data stored in a central location can be accessed through a distributed data management system. In addition, inclusion of both the raw and summarized data in the system reduces cost that could be incurred while conducting a reanalysis. Furthermore, details such as study characteristics, sampling methods, data format, quality control procedures, and how to access information are easily accessible through a data management system. Data management techniques are essential in monitoring of the quality of surface water. Consequently, they require proper funding to ensure the data management system is working without any interruptions.
E.coli is the most common indicator bacteria used for investigating the hygienic quality of surface waters. In the past, the total coliform bacteria were used to determine the quality of waters, but many limitations have been observed in their application, in surface waters. E.coli is particularly sensitive to water quality variables thus provides a reliable picture of the water quality levels. However, one of the major shortfalls of using coliform bacteria as indicators is that it does not provide an estimate of the human pathogenic viruses present in the water bodies (National Research Council 126). Hagedorn, Blanch, and Harwood (455) suggest other alternative indicators that can be used in assessing quality of surface waters and other recreational waters. These include Clostriduim perfringens, Bacteroidales, coliphage, and Staphylococcus aureus.
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