Multivariate statistical methods for analysis of physicochemical and microbiological parameters of well water from the village M’Pody

Abstract

Abstract The pollution of surface water and groundwater is a real public health problem that is currently receiving particular attention throughout the world. The use of water for food or hygiene purposes requires excellent physicochemical and microbiological quality. Well water is used for many purposes by the inhabitants of M’pody, a village in the Anyama district of Côte d’Ivoire. In this village, an epidemic of diarrhoea was detected in January 2020. This epidemic claimed sixty-nine (69) victims. This study aims to evaluate well water quality controls using the methods of principal component analysis (PCA), correspondence factorial analysis (CFA), analysis of variance (ANOVA) and self-organizing map (SOM) algorithm. The parameters studied were, turbidity (Tur), conductivity (Cond), hydrogen potential (pH), temperature (T), nitrate ( $$NO_{3^{-}}$$ N O 3 - ), nitrite ( $$NO_{2^{-}}$$ N O 2 - ), ammonium ( $$NH_{4^{+}}$$ N H 4 + ), phosphates ( $$PO_{4}^{3^{-}}$$ P O 4 3 - ), chlorides $$(Cl^{-})$$ ( C l - ) , total hydrotimetric degree (DHT), sulfates ( $$SO_{4}^{2^{-}}$$ S O 4 2 - ), bicarbonate ( $$HCO_{3^{-}}$$ H C O 3 - ), total alkalinity contents (TAC), escherichia coli (E.coli), thermotolerant coliforms (CTH) and enterococcus faecalis (E.faecalis). Data were collected from seventy-two (72) wells in the village during four campaigns in 2020. Physicochemical parameters were determined by electrochemical and spectrophotometric methods. Microbiological analysis was carried out using membrane filtration technique. Descriptive statistics revealed that Tur, Cond, pH and T parameters did not meet world health organization (WHO, 2017) standards. However, the parameters $$NO_{3^{-}}$$ N O 3 - , $$NO_{2^{-}}$$ N O 2 - , $$NH_{4^{+}}$$ N H 4 + , $$PO_{4}^{3^{-}}$$ P O 4 3 - , $$Cl^{-}$$ C l - , DHT, TAC, $$SO_{4}^{2^{-}}$$ S O 4 2 - and $$HCO_{3^{-}}$$ H C O 3 - comply with WHO standards. The results of bacteriological analyzes confirm the presence in very significant numbers of indicators of faecal contamination (CTH, E.coli and E.faecalis) in all wells. The logical explanations for faecal pollution would come from the infiltration of septic tanks located near the wells and the run-off of waste water carrying human and animal faecal matter. The diarrhea epidemic would therefore be caused by the consumption of this polluted water. PCA, FCA and hierarchical cluster analysis (HCA) were jointly employed to identify the structure of wells and deduce the principal factors controlling the parameters of these well waters. ANOVA revealed the effect of human-induced activities as the main factors influencing the physicochemical and microbiological parameters of the studied well waters. Further studies should focus on multivariate statistical techniques for effective forecasting and monitoring of emerging pollution for improved water quality.

Keywords

• Principal component analysis
• Factorial correspondence analysis
• Analysis of variance
• Self-organizing map