Abstract:
River ecosystems are essential in providing many ecosystem services including water for domestic use, irrigation, and aquaculture purpose among others. However, they are continuously degraded due to pollution from anthropogenic activities such as cage fish farming, agriculture, mining, as well as industrial and municipal wastewater discharge to mention but a few. This study therefore aimed to assess the physico-chemical parameters of a section of river Nile in Namasagali and elucidate its suitability for algal productivity in high rate algal pond system (HRAP). The specific objectives were to: i) determine the physico-chemical water quality parameters and ii) evaluate the suitability of water quality for use in HRAP to support algal productivity.
This study was conducted using a pilot scale HRAP system at Namasagali campus, Busitema University. The HRAP system was fed with water from the littoral zone of river Nile, directly pumped into the reservoir tanks. Weekly samples were collected from the HRAP inlet for a period of two months i.e., from 25th January to 29th March, 2023.
Physical-chemical variables including water temperature, dissolved oxygen (DO), total dissolved oxygen (TDS), electric conductivity (EC), and pH were measured in-situ using Multiparameter probe model: HANNA I98194. Nutrients particularly Nitrogen and Phosphorus species and Total suspended solids (TSS) were analyzed in the laboratory following APHA (1995) standard guidelines for water and wastewater treatment.
Results showed that physicochemical and nutrients concentrations were highly variable during the sampling period and these were: temperature: 23.43-29.59 oC (26.59±0.58oC), DO: 1.02-3.72 (2.67±0.23mg/L), pH: 6.88-8.63 (8.21±0.17), EC: 97-126.33 μS/cm (102.20±2.71μS/cm), TDS: 49-63.67mg/L (51.30±1.38 mg/L), NO2—N: 0.18-0.25 mg/L (0.21±0.01mg/L), NO3-N: 0.18-0.65 mg/L (0.33±0.04 mg/L), NH4 + -N: 0.17-0.35 mg/L (0.23±0.02 mg/L), SRP: 9.83-16.15 mg/L (11.08±0.60 mg/L) and TSS: 6.67-30.00 mg/L (13.67±2.25 mg/L).
Further analysis revealed that the most critical parameters were within the range required to support algal productivity in a HRAP system.
In conclusion, the study revealed that the water quality from river Nile in Namasagali area is suitable for use to support algal productivity in a HRAP system. However, it is recommended that further studies should investigate the COD river water quality and algal productivity in a HRAP system before full-scale implementation.
