Water quality studies using fuzzy-analytic hierarchical procedure method to identify their suitability for drinking, industry, and agriculture – a case study

• Published in: Desalination and water treatment 2021-06, Vol.226, p.25-36
• Main Authors: Moghadam, Enayatollah Adeli, Derikvand, Ehsan, Eslami, Hossein, Kharazi, Hossein Ghorbanizadeh, Razaz, Majid
• Format: Article
• Language: English
• Subjects: Analytic hierarchical procedure method; Fuzzy method; Langelier saturation index; Metal index; Ryznar stability index; Water quality
• ISSN: 1944-3986; 1944-3986
• DOI: 10.5004/dwt.2021.27065

Given the importance of assessing water quality in arid and semi-arid regions, the purpose of this study is to investigate water quality in Kohgiluyeh and Boyer-Ahmad Province, Iran, using fuzzy-analytic hierarchical procedure (FAHP) and the geographic information system. To this end, various parameters counting on potassium, sodium, magnesium, calcium, chloride, and sulfate content as well as PH levels, total dissolved solids in water, sodium absorption ratio, and alkalinity levels were extracted for 35 wells in the study region. These parameters were fed as input data for assessing the quality of water in regards to different usages. Through geostatistic methods (inverse distance weighted), water quality zoning maps were procured for each respective parameter affecting water quality. Upon generation of the respective zoning maps, fuzzy membership functions were used to homogenize each layer so as to obtain fuzzy maps for different parameters. The AHP technique was ultimately employed to overlay the fuzzy maps and generate the final water quality zoning map of the study area. The Langelier saturation index (LSI), the metal index (MI), and the Ryznar stability index (RSI) were also incidentally used as the prime indicators for assessing water quality for both industrial and agricultural purposes. The results of the LSI index showed that most of the studied areas are in the sedimentation class that indicates high pollution. RSI values were obtained between 6 and 8 where the eastern regions had an RSI of less than 6, the southern regions had an RSI of 6 to 7 and the northern regions had an RSI of more than 7. The results also showed that LSI in the northern regions is greater than zero, which indicates a corrosive state, and in the eastern part it is equal to zero which is indicative of the neutral state. The MI zonation map showed that the areas in the south have values greater than 1 which shows the low quality of water in these areas in terms of drinking. Residual sodium carbonate levels in the southern regions with values higher than 2 meq/L indicate low water quality in these regions. Finally, the results of the fuzzy method showed that the areas located in the eastern parts of the region have a better quality than the northern and western regions. According to the results, it is clear that in areas where there is agriculture or urban lands, pollution is high.