Effectiveness of phytoremediation in water treatment using sunflower plants (Helianthus annuus) in Buhera District, Manicaland Province, Zimbabwe

Abstract

The greatest battle that the earth has to consistently and persistently fight to maintain its natural purity is mainly human-induced pollution, especially of natural water bodies like oceans, seas, rivers and underground reservoirs. This research was conceptualised and motivated by the ever-increasing problem of insufficient and poor water quality in Zimbabwe, Manicaland province in general and Buhera district in particular. The purpose of the study was to assess the effectiveness of environmentally-friendly water treatment technologies to meet Sustainable Development Goal number 6, which aims to “ensure availability and sustainable management of water and sanitation for all” by the year 2030. While the industrial revolution has brought with it massive improvements in water treatment methods that are both faster and effective, most rural communities in the developing world have not benefited from this human ingenuity and thus continue to grapple with the challenges of access to clean and safe drinking water. The use of sunflower plants (Helianthus annuus) for domestic water treatment as an alternative to conventional and top-notch technologies was considered very necessary for water treatment especially at the household level. The research design was predominantly experimental and observational thus generating primary data. To achieve this, a set of objectives was laid out while relevant hypotheses were also propounded. Analysis of raw water collected from different sources of domestic water within the study area was done for the three seasons prevalent in the area. Collected data was systematically arranged in tables and graphs and then subjected to both descriptive statistics (means and standard deviations) and inferential statistical analysis including ANOVA single factor as well as a correlation of analysis for hypothesis testing. The three microbial pathogens namely; Escherichia coli, faecal coliform and total coliforms were subjected to extracts from four sunflower plant parts, which included; seed, leaf, stem and root tissues. The extracts were obtained using five solvents that are; chloroform, ethanol, hexane, water and acetone. The highest potential was obtained from chloroform extract followed by ethanol, water and acetone while there was no recorded effect from the solvent hexane. Throughout the experiments, sunflower seed extracts showed a greater effect on all three bacterial species. The anti-microbial properties of the sunflower seed extracts portrayed a high mean zone of inhibition of 5.7 mm and 6.3 mm on faecal coliforms and E. coli bacteria respectively. In addition, the coagulant properties of sunflower extracts were tested against turbidity and pH with different dosages of the seed, root, stem and leaf extracts at different time intervals. The seed extract was found to have an optimum dosage of 4 g at 80 minutes with turbidity removal efficiencies of 95%. The effectiveness of the extracts varied from season to season, with summer having the higher percentages while winter had the lowest percentage reductions. Results revealed that sunflower seed extract should be the first option in choosing natural materials as anti-microbial and coagulant agents. Therefore, the study concludes that sunflower seed extracts can be used as anti-microbial and coagulant agents at the household level. However, an evaluation of the toxicity of the concentration of the treatment extracts to humans based on in vivo experiments is very important to ascertain their effectiveness and use at the household level.