Application of solar pasteurization for the treatment of harvested rainwater

Reyneke, Brandon (2017-03)

Thesis (MSc)--Stellenbosch University, 2017.

Thesis

ENGLISH ABSTRACT: Rainwater harvesting has been earmarked by South African governmental authorities as an intervention strategy that could alleviate the pressures on existing centralised water distribution systems, especially in rural areas and urban informal settlements, where insufficient waste removal and potable water infrastructure are available. However, numerous studies have indicated that harvested rainwater may not be safe to use for all daily water requirements, as numerous chemical and microbial contaminants may be associated with stored tank water. Rainwater treatment technologies, including solar pasteurization (SOPAS), have subsequently been investigated (Chapter 1). In order to determine whether decentralised rainwater harvesting SOPAS systems may be a viable alternative in providing the inhabitants of informal settlements with a supplementary water source, two small- (Sites 1 and 2) and one large-scale (Site 3) rainwater harvesting SOPAS systems were installed in Enkanini informal settlement, Stellenbosch, South Africa (Chapter 2). The microbial and chemical quality of the unpasteurized and pasteurized (produced by the respective systems) rainwater was monitored using conventional water quality monitoring techniques, including the culturing of indicator organisms, screening for selected indigenous rainwater pathogens using the polymerase chain reaction (PCR) and quantitative PCR (qPCR) assays and the monitoring of anion and cation concentrations. Additionally, the operational sustainability of the systems and water usage by the participating households were monitored. Chemical analyses indicated that all anions and cations were within the limits stipulated by various national and international drinking water quality guidelines, with the exception of zinc which contravened the respective guidelines before (mean: 3919 μg/L) and after (mean: 3964 μg/L) pasteurization at both Sites 1 and 2. In addition, the arsenic concentrations measured at Site 3 before (mean: 18.69 μg/L) and after (mean: 18.30 μg/L) pasteurization exceeded the respective drinking water guidelines. The increased zinc concentrations were attributed to the galvanised zinc roofing material installed at Sites 1 and 2, while the increased arsenic concentrations may be attributed to a roofing treatment or paint utilised to cover the catchment area at Site 3. Microbial analyses indicated that pasteurization temperatures of 53 °C (small-scale systems) and 55 °C (large-scale system) were required to reduce Escherichia coli and total and faecal coliforms to below the detection limit [< 1 colony forming units (CFU)/100 mL]. However, minimum pasteurization temperatures of 66 °C (small-scale systems) and 71 °C (large-scale system), were required to reduce the heterotrophic plate count (HPC) to within drinking water limits (1.0 × 104 CFU/100 mL). Of the opportunistic pathogens detected using PCR assays, Legionella spp. was the most prevalent pathogen detected in the small-scale systems [unpasteurized (100%) and pasteurized (91%)] and the large-scale system [unpasteurized (83%) and stored pasteurized tank water (100%)]. Quantitative PCR analysis then indicated that while the gene copies of Legionella spp., Pseudomonas spp. and Salmonella spp. were reduced during SOPAS, the organisms were still detected at the highest pasteurization temperatures analysed for each site (Site 1 – 85 °C; Site 2 – 66 °C; Site 3 – 79 °C). Additionally, the application of a metabolic responsiveness adenosine triphosphate (ATP) assay (BacTiter-GloTM Microbial Cell Viability Assay) indicated the presence of metabolically active cells in all pasteurized rainwater samples analysed. Results also indicated that the systems required limited maintenance and the small-scale systems in particular were able to provide the participating households with an alternative warm water source that could be utilised for numerous domestic purposes. As various limitations have been associated with the use of culture-based analyses for the monitoring of water quality, the aim of Chapter 3 was to compare molecular-based viability assays [ethidium monoazide bromide (EMA)-qPCR, propidium monoazide (PMA)-qPCR and DNase treatment in combination with qPCR] as well as the metabolic responsiveness ATP assay to culturing analysis for their ability to accurately determine cell viability in bacterial monocultures following heat treatment. Three Gram-negative (Legionella spp., Pseudomonas spp. and Salmonella spp.) and two Gram-positive (Staphylococcus spp. and Enterococcus spp.) bacteria commonly associated with water sources were selected as test organisms. Of the various concentrations of EMA and PMA analysed, 6 μM EMA and 50 μM PMA were identified as the optimal dye concentrations as low log reductions were recorded (viable and heat treated samples) in comparison to the no viability treatment control. Comparison of the results obtained for all the molecular viability assays (6 μM EMA, 50 μM PMA and DNase treatment) then indicated that the 6 μM EMA concentration was comparable to both the 50 μM PMA and the DNase treatment for the analysis of most of the test organisms (viable and heat treated). In addition, the results for the culturing analysis (CFU) of the viable S. typhimurium as well as the viable and heat treated samples of L. pneumophila and P. aeruginosa were comparable to the gene copies detected using molecular-based viability assays. However, the CFU in the heat treated samples of S. typhimurium were significantly lower than the gene copies detected using DNase in combination with qPCR, with no gene copies or CFU detected in the heat treated samples of S. aureus and E. faecalis. In contrast, while the ATP assays indicated the presence of metabolically active cells in the viable and heat treated samples, the ATP assay also indicated the presence of metabolically active cells in samples that had been autoclaved (negative viability control). It was thus concluded that molecular-based assays may be used to supplement culture based analysis for the comprehensive identification of the viable microbial population in water samples (before and after treatment).

AFRIKAANSE OPSOMMING: Die oes van reënwater is deur Suid-Afrikaanse regeringsowerhede as 'n ingrypingstrategie geïdentifiseer, wat die druk op die bestaande gesentraliseerde waterverspreidingstelsels kan verlig, veral vir landelike gebiede en informele nedersettings waar onvoldoende vullisverwydering en drinkwater-infrastruktuur beskikbaar is. Talle studies het egter aangedui dat ge-oeste reënwater nie veilig vir alledaagse watervereistes is nie weens talle chemiese en mikrobiese kontaminante wat met gestoorde tenkwater geassosieer word. Reënwater-behandelingstegnologieë, insluitende sonkragpasteurisasie (SOPAS), is dus ondersoek (Hoofstuk 1). Om vas te stel of gedesentraliseerde reënwater-oesting SOPAS sisteme vir die inwoners van informele nedersettings ‘n aanvullende bron van water op ‘n lewensvatbare wyse kan voorsien, is twee klein- (Terrein 1 en 2) en een grootskaalse (Terrein 3) reënwater oesting SOPAS sisteme in Enkanini, Stellenbosch, Suid Afrika, geinstalleer (Hoofstuk 2). Die mikrobiese en chemiese kwaliteit van die gepasteuriseerde en ongepasteuriseerde (deur die onderskeie sisteme geproduseer) reënwater is met behulp van konvensionele waterkwaliteit analises gemonitor, wat die groei van indikator-organismes, die toetsing vir geselekteerde inheemse reënwaterpatogene met polimerase kettingreaksie (PKR) en kwantitatiewe PKR (kPKR) en die bepaling van anioon- en katioon konsentrasies, insluit. Daarbenewens is die operasionele volhoubaarheid van die sisteme en die waterverbruik van die betrokke huishoudings gemonitor. Chemiese analises het aangedui dat al die anioon- en katioon konsentrasies binne die limiete van die verskeie nasionale en internasionale drinkwater riglyne was, met die uitsondering van sink wat die onderskeie riglyne voor (gemiddeld: 3919 μg/L) en na (gemiddeld: 3964 μg/L) pasteurisasie by beide Terrein 1 en 2 oorskry het. Daarbenewens het die arseen konsentrasies by Terrein 3 voor (gemiddeld: 18,69 μg/L) en na (gemiddeld: 18,30 μg/L) pasteurisasie ook die onderskeie drinkwater riglyne oorskry. Die verhoogde sink konsentrasies is toegeskryf aan die gegalvaniseerde sinkplate wat as dakoppervlak by Terrein 1 en 2 gebruik is, terwyl die verhoogde arseen konsentrasies aan die verf of behandeling van die dak by Terrein 3 aangewend is, toegeskryf is. Die mikrobiese analises het aangedui dat pasteurisasie temperature van 53 °C (kleinskaalse sisteme) en 55 °C (grootskaalse sisteem) nodig is om Escherichia coli en totale en fekale kolivorme tot onder die opsporingslimiet [< 1 kolonie vormende eenhede (KVE)/100 mL] te verminder. Minimum pasteurisasie temperature van 66 °C (kleinskaalse sisteme) en 71 °C (grootskaalse sisteem) is egter nodig om die heterotrofiese plaattelling (HPT) tot binne die limiete van die drinkwater riglyne (1.0 × 104 KVE/100 mL), te verminder. Die PKR analises het aangetoon dat Legionella spp. die mees algemene patogeen in beide die kleinskaalse [ongepasteuriseerde (100%) en gepasteuriseerde (91%)] en grootskaalse sisteme [ongepasteuriseerde (83%) en gestoorde gepasteuriseerde tenkwater (100%)] was. Die kPKR analises het aangedui dat terwyl die geenkopieë van Legionella spp., Pseudomonas spp. en Salmonella spp. tydens SOPAS verminder is, die organismes steeds by die hoogste pasteurisasie temperatuur van elke terrein (Terrein 1 – 85 °C; Terrein 2 - 66° C; Terrein 3 - 79° C) teenwoordig was. Daarby het die metaboliese responsiwiteit adenosien trifosfaat (ATP) toets (BacTiter-GloTM Microbial Cell Viability Assay) aangedui dat metabolies- aktiewe selle in al die gepasteuriseerde reënwatermonsters teenwoordig was. Die resultate het ook aangedui dat die sisteme minimale onderhoud nodig gehad het en dat die kleinskaalse sisteme die huishoudings met ‘n alternatiewe warm waterbron kon voorsien, wat vir verskeie huishoudelike take gebruik kon word. Verskeie beperkings word geassosieër met die gebruik van groei-gebaseerde analises om waterkwaliteit te monitor. Die doel van Hoofstuk 3 was dus om molekulêr-gebaseerde lewensvatbaarheidstoetse [ethidium monoasied bromied (EMA)-kPKR, propidium monoasied (PMA)-kPKR en DNase-behandeling in kombinasie met kPKR] en die metaboliese responsiwiteit ATP toets met groei-gebaseerde analises, te vergelyk in terme van hul vermoë om sel lewensvatbaarheid in bakteriële monokulture na hitte-behandeling te bepaal. Drie Gram-negatiewe (Legionella spp., Pseudomonas spp. en Salmonella spp.) en twee Gram-positiewe (Staphylococcus spp. en Enterococcus spp.) bakterieë, wat algemeen met waterbronne geassosieer word, is as toets organismes gekies. Verskeie EMA en PMA konsentrasies is getoets met 6 μM EMA en 50 μM PMA wat as die optimale konsentrasies geïdentifiseer is op grond van die lae log-vermindering wat opgemerk is (lewensvatbare en hitte-behandelde monsters) in vergelyking met die nie-lewensvatbare kontrole. Vergelyking van die resultate wat vir al die molekulêre lewensvatbaarheidstoetse (6 μM EMA, 50 μM PMA en DNase behandeling) verkry is, het aangedui dat 6 μM EMA met beide die 50 μM PMA en die DNase behandeling vir meeste van die toets organismes (lewensvatbaar en hitte behandeld) vergelykbaar was. Daarbenewens was die groei-gebaseerde analise (KVE) van S. typhimurium en die lewensvatbare en hitte-behandelde L. pneumophila en P. aeruginosa vergelykbaar met die geenkopieë wat met die molekulêre lewensvatbaarheidstoetse verkry is. Die KVE in die hitte-behandelde S. typhimurium monsters was egter beduidend laer as die geenkopieë wat met die DNase in kombinasie met kPKR analise verkry is, terwyl daar nie geenkopieë of KVE in die hitte-behandelde S. aureus of E. faecalis monsters verkry kon word nie. In teenstelling, alhoewel die ATP toets aangedui het dat metabolies-aktiewe selle in die lewensvatbare en hitte behandelde monster teenwoordig was, het die toets ook aangedui dat daar metabolies-aktiewe selle in die ge-outoklaveerde monsters was (die negatiewe lewensvatbare kontrole). Dus kan molekulêr-gebaseerde toetse gebruik word om groei-gebaseerde toetse vir die omvattende identifikasie van die lewensvatbare mikrobiese populasie in water monsters (voor en na behandeling) aan te vul.

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