Sufficient provision of clean drinking water is an essential need for sustaining human-well being. The majority of people suffering from lack of clean water reside in less developed communities, where the financial and technical barriers hamper the implementation of modern water-sanitation systems. The goal of this study is to evaluate hydrochar derived from selected organic wastes as a low cost adsorbent for pathogen removal in water treatment. Pathogen removal efficiency was measured by carrying out breakthrough analysis using a simple 10 cm sand filtration set-up supplemented with hydrochar (1.5 % w/w).
Two home-made two-step reverse transcription-quantitative polymerase chain reaction assays were developed using either RevertAid or MMLV reverse transcriptase. Both assays showed competitive efficiency to a selected commercial one-step master kit on analyzing environmental and laboratory samples. The costs of home-made assays were 11 times less than the commercial kit. Successive virus removal experiments were carried out using the home-made assay based on the RevertAid reverse transcriptase.
We evaluated the Escherichia coli (E. coli) removal efficiency of hydrochars derived from agricultural residue of maize and stabilized sewage sludge from wastewater treatment plant. Though raw hydrochars showed relatively limited E. coli removal efficiency of ~70 % for maize-hydrochar and ~20 % for sewage sludge-hydrochar, a simple cold-alkali activation of hydrochars using 1M KOH solution enhanced E. coli removal efficiency of both hydrochars (~90 %). Apparently, KOH activation of raw hydrochar removed alkali-soluble and tar-like substances from hydrochar surface, exposing more hydrophobic core and developing more porous surface structure. Also, removal of pathogenic rotavirus and adenovirus were investigated using hydrochar produced from sewage sludge and swine waste. Raw hydrochars (without activation) successfully removed both viruses at efficiencies higher than 99 %. Successive material characterization results suggested that the supplements of the hydrochar adsorbents provided a larger contact surface area with strong hydrophobicity in the sand media, facilitating adsorptive removal of pathogenic microorganisms.
This PhD study suggests the potential of hydrothermal carbonization as a technical solution for water-sanitation issues. Through hydrothermal carbonization, hazardous solid wastes containing pathogenic microorganisms will be totally sanitized, and the resulting hydrochars can be used as a pathogen barrier in water and / or wastewater treatment systems.