Pathogen removal using saturated sand colums supplemented with hydrochar

Description

Lack of clean water is one of the most important public health challenges in less developed communities. Due to insufficient financial and technical resources in places in need, development of low-cost water treatment technologies can play a key role in sustainable water provision. In this context, this PhD research investigated the removal of pathogenic microorganisms in simple sand filtration set-ups supplemented with low-cost adsorbents (hydrochar) produced via hydrothermal carbonization of biowastes. Two types of hydrochar, derived from hydrothermal carbonization of agricultural residue of maize and stabilized sewage sludge from wastewater treatment plant, were evaluated as adsorbents for Escherichia coli removal in saturated sand columns. The removal efficiency of sand columns amended with these adsorbents improved from 20-70% to ~90 % by alkali activation carried out in room temperatures using 1 M potassium hydroxide solution. This PhD research also demonstrates the removal of human pathogenic viruses in sand columns supplemented with hydrochar adsorbents derived from stabilized sewage sludge and fresh swine waste. In order to enumerate human pathogenic rotavirus and adenovirus in virus removal experiments, low-cost polymerase chain reaction assays were developed under this PhD study. These assays show a competent performance in analyzing virus concentrations in both laboratory and environmental samples. Amendment with either hydrochar (without alkali activation) in sand columns was able to remove more than 99% of both viruses. Content: 1 General introduction 1.1 Background 1.2 Research scope and objectives 1.3 Thesis outline 1.4 References 2 Literature review 2.1 Hydrothermal carbonization 2.2 Test microorganisms 2.2.1 Escherichia coli 2.2.2 Rotavirus 2.2.3 Adenovirus 2.3 Polymerase chain reaction technologies 2.4 Mechanisms for colloid retention in porous media 2.5 References 3 Development of low cost two-step reverse transcription- quantitative polymerase chain reaction assays for rotavirus detection in foul surface water drains 3.1 Introduction 3.2 Methods and materials 3.2.1 Primers and probe 3.2.2 Standard virus stock for regression curves 3.2.3 Environmental virus samples 3.2.4 Nucleic acid extraction 3.2.5 Commercial one-step RT-qPCR assay 3.2.6 Home-made two-step RT-qPCR assay with M-MLV 3.2.7 Reagent dose optimization in the two-step home-made assay with M-MLV 29 3.2.8 Home-made two-step RT-qPCR assay with RevertAid 3.3 Results 3.3.1 DTT in the RT buffer used in the home-made assay with M-MLV 3.3.2 Standard curves from rotavirus Wa 3.3.3 Inhibition in the environmental samples 3.3.4 Optimization of the reagent dose 3.3.5 Performance of the home-made M-MLV based and RevertAid based assays 36 3.4 Discussion 3.5 References 4 Removal of Escherichia coli from Saturated Sand Columns Supplemented with Hydrochar Produced from Maize 4.1 Introduction 4.2 Methods and materials 4.2.1 Bacterial suspension 4.2.2 Hydrochar 4.2.3 Column experiments 4.2.4 Material characterization 4.3 Results 4.3.1 Adsorbent selection 4.3.2 Material characterization 4.3.3 Breakthrough analyses 4.4 Discussion 4.4.1 Effect of KOH activation on hydrochar 4.4.2 Reversibility of E. coli attachment to hydrochar 4.4.3 Suggestions for the further research 4.5 References 5 Removal of Escherichia coli from saturated sand columns with intermittent operation supplemented with hydrochar derived from sewage sludge 5.1 Introduction 5.2 Methods and materials 5.2.1 Escherichia coli suspension 5.2.2 Hydrochar 5.2.3 Material characterization 5.2.4 Column experiments 5.3 Results 5.3.1 Material characterization 5.3.2 E. coli flushing test 5.3.3 E. coli removal efficiency in large column experiments 5.4 Discussion 5.4.1 Effect of KOH activation of hydrochar on E. coli removal 5.4.2 Effect of idling time on E. coli removal efficiency 5.4.3 Potential of application in HTC-sand filter for pathogen removal 5.5 Conclusions 5.6 References 6 Removal of rotavirus and adenovirus from artificial ground water using hydrochar derived from sewage sludge 6.1 Introduction 6.2 Methods and materials 6.2.1 Hydrochar and characteristics 6.2.2 Virus stock and influent preparation 6.2.3 Virus enumeration 6.2.4 Column preparation 6.2.5 Design of virus removal experiments 6.3 Results 6.3.1 Calibration curves 6.3.2 Breakthrough analyses 6.4 Discussion 6.4.1 Effect of hydrochar supplement on virus removal in sand columns 6.4.2 Role of secondary energy minimum 6.4.3 Effect of humics in the feed solution 6.4.4 (RT)-qPCR technology for virus quantification in water treatment 6.5 References 7 Simultaneous removal of rotavirus and adenovirus from artificial ground water using hydrochar derived from swine faeces 7.1 Introduction 7.2 Methods and materials 7.2.1 Hydrochar 7.2.2 Virus suspension 7.2.3 Virus quantification 7.2.4 Material characterization 7.2.5 Column experiments 7.3 Results 7.3.1 Hydrothermal carbonization of swine waste 7.3.2 Material characterization 7.3.3 Column experiments 7.4 Discussion 7.4.1 Improved virus removal with hydrochar supplement in sand columns 7.4.2 Effect of flow rate and secondary energy minimum 7.4.3 HTC for faecal waste treatment 7.5 Conclusions 7.6 References 8 General discussion and conclusions 8.1 PCR-based methods for pathogen removal assessments 8.2 Hydrochar application in water treatment 8.3 Hydrothermal carbonization for sewage sludge treatment 8.4 Hydrothermal carbonization for sanitation and water treatment 8.5 Conclusions 8.6 References