Seasonal variation of organic matter concentration and characteristics in the Maji ya Chai River (Tanzania): Impact on treatability by ultrafiltration

Abstract

Many waters in Tanzania exhibit high concentrations of organic matter and dissolved contaminants such as fluoride. Due to bacteria and virus removal, ultrafiltration (UF) is an attractive option for drinking water treatment, and when coupled with adsorbents, may compete with other established processes like nanofiltration (NF) for lower contaminant concentrations. The results presented here examine the characteristics and treatability of tropical natural organic matter (NOM) by UF as a function of seasonal variation. The Tanzanian river Maji ya Chai was sampled monthly during one year. The composition of NOM in Maji ya Chai River is influenced strongly by precipitation. Total organic carbon (TOC), specific ultraviolet absorbance (SUVA) and concentration of allochthonous organics substances (such as humic substances (HS)) are elevated in periods following high precipitation, while TOC is lower and contains more biopolymers in the dry seasons. UF experiments with two regenerated cellulose membranes of different molecular weight cut-off (MWCO, 5 and 10 kDa) were conducted. UF is able to remove 50-95% of TOC with a seasonal variability of 10-20%. Due to the remaining NOM in the water that would contribute to disinfection by-product formation and bacterial regrowth, the physically disinfected water is more applicable for point of use systems than distribution or storage.

Drinking Water Treatment and Challenges in Developing Countries

“…• Some non-harmful contaminants may influence the taste, smell, colour and turbidity of water and make it unacceptable to the consumer; its examples include zinc, iron, particulate matter and humic material [9].…”

Characteristics of NOM Released to Water from Different Forest and Agricultural Soils

“…This is different from the findings of Guigue et al [3], who has reported that the SUVA of NOM extracted from forest soils was lower than that from cropland soils, indicating that the content of aromatic organic molecules contained in and released from soils is affected by the type of soil origin and the pH of water [3]. In addition, compared to the SUVA of dissolved OM in reservoir, lake and river water [1,6,7], the SUVA of the released NOM under neutral condition in this study was larger. For instance, the SUVA of NOM in Maji ya Chai River …”

“…Naturally, humic substances (humic and fulvic acids) and proteinlike substances are the major components and pH plays a predominant role in determining the final properties of the released NOM in water [1][2][3]. Guigue, et al [3] have reported that the pH of NOM solution released from different types of soil origin, i.e.…”

“…Regarding the composition of NOM, in addition to the index of specific ultraviolet absorbance (SUVA), which reflects the extent of aromaticity of the constituting components [1,2,6,7], fluorescence excitation-emission matrix (EEM) spectroscopy is increasingly used to generate information that cannot be achieved either by TOC, UV260 or SUVA [8][9][10]. In addition to these, the molecular weight (MW) distribution of NOM can provide valuable information for better understanding the polydisperse nature of NOM and the removal behavior of the constituting components during various physicochemical water treatment processes [2,11,12].…”

Renewable energy-powered membrane technology in Tanzanian communities

“…Regional variation in rainfall pattern and associated turbidity or organic matter loading may be significant. 23,24 In this work, the performance of a renewable energy-powered membrane system (UF-NF) was studied with two real waters that were selected from many groundwater and surface water samples collected in remote Tanzanian communities. The aim of this research was to investigate, with real waters and on site in remote communities, the (i) impact of energy fluctuations induced by the renewable energy resource (the sun) on water quality; (ii) removal of fluoride in carbonaceous waters and (iii) implications of high organic matter content on water quality.…”