Industries produce waste that can affect the: 1  pH of water (whether it is acid, neutral or alkaline); 2  colour of water; 3  amount of nutrients (increase in nutrients can cause eutrophication);
Generally, the purpose of a review is to analyze critically a segment of a published body of knowledge through summary, classification, and comparison of prior research studies, reviews of literature, and theoretical articles.
1 In the recode file these variables are combined and created in a form that is easier to use for analysis.  Third, summary variables are often necessary in analysis and many of these, including the summary variables that are used in the DHS reports, are included in the recode file.