Water is essential for life on earth. Human society is challenged to sustain sufficient water quantity of good quality. This objective is reflected in sustainable development goal 6, “clean water and sanitation”. Water monitoring is part of sustainable water management and aims to evaluate the physical, chemical and biological status of a water body. Regular monitoring in the catchment area of Indalsälven (Sweden) is conducted by the Indalsälven Water Conservation Association (IWCA). In this area counts of Escherichia coli (E. coli) between 0 and 500 colony forming units (CFU) were monitored from 1993 – 2022 at the closest monitoring station Enkroken. This implies that drinking water quality standards were exceeded during many occasions (≥10 E. coli CFU/100ml). It is known that survival of E. coli in aquatic environments is dependent on nutrient levels, turbidity, sedimentation, pH level, predation, microbial community composition, temperature, and solar radiation. Low water depth and clear water with poor nutrient level in Enan and Handölan, tributaries to Indalsälven, are believed to cause solar radiation to be the main driver for inactivation of E. coli. Inactivation behaviour of indicator bacteria for faecal contamination such as E. col, is assumed to reflect on other bacteria that were excreted in the same way. The objective of the research was to investigate to which extent river color and river depth under the influence of sunlight affected E. coli inactivation in pristine like conditions such as the upper catchment area of Indalsälven. In this study, conditions from the research area were mimicked in 4 laboratory experiments. Results showed that neither 10 nor 35µW/cm2 led to additional inactivation due to sunlight. In a following experiment the liquid depth was reduced, with as a result that the inactivation of bacteria started to be influenced by sunlight when the depth was reduced to 14.4cm or lower. A fourth experiment was conducted at 14.4cm depth and additional color concentration 50 and 100 mg/l Pt. Results indicated that inactivation influenced by sunlight was reduced at color level 50 or more to a level that was equal to no sunlight radiation. A median depth of 0.2 cm and median color level of 15 mg/l Pt in the catchment area of Indalsälven suggests that inactivation of E. coli is very likely influenced by the sun, upstream the measuring point Enkroken and at points where the river is as shallow 14.4cm or less. Sunlight radiation might be underestimated in the conducted laboratory experiments, therefore continuous on-site research is suggested. / <p>2022-06-19</p>
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:miun-47407 |
| Date | January 2022 |
| Creators | Student 1, efternamn:Szépfalusi, Béla |
| Publisher | Mittuniversitetet, Institutionen för ekoteknik- och hållbart byggande |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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