This paper studied evaluation of surface water pollution from industrial and municipal waste water by using GIS and remote sensing applications and theories. The article has stated that GIS and remote sensing techniques and application are used in monitoring and evaluation of water pollution from discharge wastewater from industries and municipal sewer system because they provide spectral, spatial and temporal information. The principal merits of using the application have been outlined as extensive coverage into regions that are not easily physically accessible. On the other hand, the confusion of the phenomenon that occurs in the maps and image has been cited as the major drawback. The study also stated that the primary strategy to overcome the drawbacks was confirmation of the data and use of standard expertise. Lastly, the paper has recommended the use of GIS and remote sensing as they provide a flexible analysis of the needed data.

Introduction

Surface water pollution is the contamination of the water that occurs on the surface of the earth as the streams, lakes, rivers, seas and ocean water. The contamination occurs when pollutants that contain hazardous substances are discharged into these water bodies without being treated. In the recent past, the assessment of surface water pollution has been high due to the increased alarming level of pollutant discharged into the surface water. The pollution has destroyed the ecosystem and posed a health risk to animals, plant, and humans. Many governments have put emphasis on regulating the level of water pollution, for this to be done more efficiently than the pollutant deposited in the water bodies have to be detected and analysed. Remote sensing and GIS give the perfect solution to the problem of detection as they sense and analysis this pollutant even when not in contact.

Remote sensing is the art or science used to obtain information about areas, phenomena or object by analysing data that are acquired by a device, not in contact with the said area, object or phenomenon of investigation. On the other hand, GIS (geographical information system) is a computer system that usually captures, store, check and display data that relate to a position on the earth’s surface. The data enable analysis and understanding of patterns and relationships. The use of remote sensing and GIS in solving water pollution started when the first satellite was launched. These tools proved to be effective as they provided spatial, spectral and temporal data on large surfaces of water even those which were inaccessible. This essay will explain the use of GIS and Remote Sensing Techniques and applications in monitoring and evaluation of water pollution from discharge wastewater from industries and municipal sewer systems. In addition, the advantages and challenges of using GIS and Remote Sensing Techniques in assessing surface water pollution from these two sources and the strategies for overcoming obstacles will also be discussed.

Industrial waste water

The integration of both GIS and the remote sensing has been broadly applied as a powerful and useful monitoring tool for the detection of waste water from industries. Many researchers have used remote sensing and GIS in their studies in analysing and monitoring industrial water waste. When both methods integrated, they have proved to be the cheapest way in which more detailed data can be accessed that is not readily available on the earth's surface.

A research conducted in the city of Baghdad was used to determine the effectiveness of using the GIS and the remote sensing in monitoring the industrial water waste in the city. The report concluded that GIS and remote sensing instruments when integrated, they formed a very beneficial mean of developing maps that demonstrated the danger posed by industrial water like oil spillage. The report also added that the use of GIS and remote sensing enabled detection of every kind of insoluble waste pollution caused by industries by use of thematic maps.

Another research was carried out to assess the level of industrial water waste in the Jordan River. The report aimed at testing the effectiveness and reliability of GIS and remote sensing as a means of evaluating industrial waste water. The report concluded that the use of these tools was effective in the determination of the nature, rate and location of the industrial waste. Conducted research on how effective the imageries from GIS and remote sensing were on monitoring the industrial surface water waste. The report compares the result obtained from physical examination of the industrial water waste and those obtained by use of remote sensing and GIS instruments. It concluded that results from the two studies showed a very high positive correlation thus the imageries from the GIS, and remote sensing were as effective as those of direct examination.

The data that can be collected by use of GIS and remote sensing includes: Data on the colour of water, data on the characteristic of the habitats of animals in the affected regions, data of the changes in human use of the affected area, and data on the plant coverage change in the affected areas. The remote sensing that collects this type of data is the imageries that are occasionally taken from the satellites from time to time. These imageries can indicate changes that occur in waters around the industries, the images are stored using computers to be used in the analysis of the data. The GIS uses the images taken by use of a satellite to develop regional spatial data into a coordinated GIS database that assess the change in water uses, the characteristic of the animal’s habitats and changing crop cover change.

An example of how to use the above method can be the assessment using aircraft pictures on industrial wastewater is in the Niger Delta in Nigeria. The delta is a productive oil mining and refining area, a lot of petroleum from the mines and the refining industries spill into the river delta causing immersive pollution as indicated below by a remote sensing photos. These two photos were taken from an aircraft in 2009 and 2011 respectively, ILWIS (Integrated Land and Water Information System) a GIS software program used to analyse and assess data was used to evaluate the data.

 Several remote sensing instrument are used to assess the industrial was waste. The nature of the instruments used depends on the accessibility as well as area and nature of the evaluation. Industries discharge’s hot water to the surface water and this can be detected using a thermal remote sensor. Aerial photographs also are commonly used in assessing industrial pollution; they are taken by airborne objects like aircrafts and helicopters that take photo of the area to be evaluated. Remote sensing satellites are also used to take images when a large coverage is required. The different instrument used in assessing industrial waste using remote sensing and GIS are shown in the table below.

The first photos show a central region which has being affected by oil pollution from the nearby region. Nevertheless, the pollution as at 2009 was not extreme as it appears two years later in the year 2011. “Using a remote sensing and GIS to examine size, location and rate of change the industrial pollution waste can be evaluated”. The second photo also demonstrates the level of damage caused to the surrounding habitant like the vegetation around the area by the pollution.

Advantages and Challenges

GIS and remote sensing have numerous merits when used as a tool for assessing the pollution of surface water from the industrial waste water. When both are integrated, they provide an analysis that is flexible to enter and display data from various sources that are considered necessary for identification, change detection and database analysis of environmental features. This means that in case of industrial waste water pollution, by integrating the two methods, and then it is likely for one to identify more proof of pollution taking place by examining changes in the maps. This process also is critical as it enable assessment of industrial waste pollution even into the less accessible areas. Remote sensing and GIS tool also covers a very large region; it may be a whole lake, river or even a sea. The collection of data and analyses is cheap; one does not need to be in contact with the region to get the data. The data collected is spatial and temporal thus it shows changes in the region as per given time difference.

The main challenge faced by this method of assessment is the issue of confusion and interpretation; one needs to be extremely conversant with the practice so as to come up with an explanation that is free from error. Another challenge is that some pollution cannot be easily accessed by the remote sensing and GIS integration. This type of pollutions is caused by pollutant that is not easily detected by the pictures, and does not cause changes in the immediate environment. These can include trace metals like lead and mercury. Another challenge is that it only provides spatial and temporal data only, such data as physical data, biological and chemical data cannot be provided. This means that the only data that can be assessed is on location, rate of change and size of the pollution, but biological or chemical assessments of the pollution cannot be assessed by the method. In addition, it is also very expensive to produce large scale images of data from remote sensing and GIS and thus limiting their use. Lastly, they require trained labour for them to operate which is costly.

Waste Water from Municipal Sewer Systems

Sewage is used to refer to domestically used water, which composition included wastewater from toilets, bathrooms, washrooms and kitchen. This water needs to be treated for removal and neutralisation of the hazardous element in its composition before been drained to other water bodies. When directly drained into the environment, it flows to the nearby surface water where it causes harm to the marine life. In the recent past, researchers have used remote sensing and GIS in detecting and assessing the level of pollution produced by municipal wastewater sewer systems.

A study conducted in the municipality of the Nagercoil town in India, was meant to assess the level of suitability for determination of the degree of pollution caused by the municipal council sewer in the nearby surface water bodies by the use of geographic information system and the remote sensing. The research was a success, the GIS and remote sensing produced the perfect assessment to the pollution that was caused by the municipal sewer. The study concluded that remote sensing and GIS makes it easier for one to obtain variable information on the study area and that it gives more accurate results in comparison with other conventional methods regularly used. The report added that the GIS provide a better management of the spatial and non-spatial information that are so necessary for the evaluation and assessment of sewer pollution.

The data that is collected to examine the sewer pollution depends on the effect caused by the sewer discharged into the water. The main effect of sewer on surface water is the eutrophication due to the excessive nitrogen that is contained in the domestically used water. In addition, change in animal habitats and human activities around the surface water affected may be considered. From the above, the data that can be obtained is that which show increases plant cover in the water surface due to eutrophication, also reduction in human activities like transportation and fishing due to inaccessibility, and lastly is the change of habitat of the animals.

The images that are taken from the satellite form the primary means of data collection in the remote sensing. These images are taken at varying distance and intensity so as to provide detailed and flexible data, the data is then sent to the computer where it is stored waiting to be analysed using the geographical information system. The thematic maps of the study are then prepared by use of integrated top sheet, the images and maps from the satellite are also prepared by incorporating the utilisation of software ArcGIS 9.3. This technique enables the presentation of data by considering all the data that needs to be collected.

Several instruments and methods of remote sensing and GIS are used to collect and assess data on municipal sewer water pollution. The method used should effectively detect the eutrophication caused by the sewer in the water as well as the presence of the sewer in the water. The table below shoes the method used and the nature of data collected.

Example a case study of a satellite image from Lake Victoria in East Africa showing how the lake have been polluted by sewer from the town around its environs as illustrated below. The two images were taken from a remote sensing satellite and were analysed using Capaware GIS program. A remote sensing type of satellite was used to take the photos from the space in a period difference of six years; the interpretation was done by Capaware GIS program.

 The two images represents a six year's periods difference, the first photo was taken in 2000 while the second photo was taken in 2006.  It can be seen that the increase in chlorophyll in the lake can be assessed by this method. In 2000, the level of chlorophyll that covered the lake was of less cover in comparison to 2006. In fact using the mg/m3 measure used, most region in the margin of the lake that were largely affected by sewer, increased chlorophyll level from 30mg/m3 to 60mg/m3.

The Advantages and Challenges

The GIS and remote sensing uses both temporal and spatial data in the assessment of the extent to which sewer pollution is affecting the surface water (Khorram, 2012). These two types of data enable comparison in between given period on the location and size of the pollutant being addressed. In case of surface water pollution by the sewer, images of the eutrophication; which are algae, bacteria and plants that rapidly overpopulate if sewer pollution occurs, can be detected and the level of their increase can also be addressed. The use of GIS and remote sensing in the determination of sewer pollution is also advantageous as it provides cheap mean of data collection, it is also easily manipulated using a computer to give the desired data. The data collected covers a extensively large area it can be a lake or a sea, it is also cheap to collect this data as only photos need to be taken, the researcher does not need to be in contact with the region of survey. The images taken give information based not only on present but also on the past and this enable dynamic study.

GIS and remote sensing also face challenges in assessment of pollution caused by the sewer. The images and maps from the GIS and remote sensing sometimes are more appealing as compared to the contents warrant and thus it can be misleading sometimes. The other challenge is the misinterpretation of the data; the data may be misinterpreted if caution is not taken; thus adequate evidence should be gathered to ensure proper interpretation. This data sometimes may not be available if the pollution does not cause any physical changes to the surrounding environment that can be determined by spatial and temporal data. Remote sensing and GIS also can be expensive method if repetitive dynamic study is required, taking photo can be costly. The fact that human determine when to take photo and how to analysis it, make them also less effective. Lastly, if used in a smaller region they are very costly; it is costly to use an aircraft or a helicopter just to take a photo from a pond or a dam. Therefore, this method better works in large area coverage.

Strategies for Overcoming Obstacles

Several measures have to be taken to overcome the limitations listed above; strategies have to be laid down to help overcome them effectively. The first strategy will be the use of a lower scale when representing the information on a map. This will ensure that the limitations that arise from the line of delineation that causes freezers are avoided so as to present reliable information. If the scale level is lowered, then a much bigger map if produced which will enhance better information on surface water pollution interpretation.

The use of effective colour coding need to be put into consideration. Colour should be bright enough to ensure that distinct difference occurs in the thematic maps and also from the images taken from the remote server his can be done in way that colours are thinker in regions that are more affected by pollution either from industries or the sewer and becomes lighter in region with less or no pollution.

Confirmation also seems a very promising strategy for overcoming the said limitation; the content warrant should always be compared with the GIS and remote sensing data to ensure that inferences that lack credibility are not made. The Use of a qualified expert in the interpretation of the images and maps will also enable reliability in the information collected. It is also always difficult to incorporate line of delineation in the GIS maps thus the experts to be involved should have a total comprehension of the GIS and remote sensing method.

Conclusion

In conclusion, the use of GIS and remote sensing in assessment of pollution of surface water has gained roots in the recent past due to its wider significance as compared to the conventional used methods. This method provides a flexible analysis that is used to enter and display electronic digital data from numerous sources that are very essential for the environmental feature identification, database analysis and change detection. In addition, it allows the researchers and decision makers involved to combine the spatial, temporal and spectral data with ancillary data about the landscape. These methods then use all these sources as input data for modelling the patterns and the quantity rate of water contamination.

The essay above has indicated limitations that are experienced in the application of these two methods in assessment of pollution. It has been outlined that some pollution does not cause any direct harm to the immediate environment and thus it is very difficult using this method in the assessment of such pollution information. Additionally, the facts that this method covers even the regions that are not readily available by physical presence make it a paramount method in the determination of the surface water pollution. More research in this area needs to be conducted in the evaluation of how the assessment of pollution using GIS and remote sensing can be used in combating the surface water pollution. This may include data on the most effective places to construct the treatment centre for the sewer and the industrial water waste.

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