Abstract
Ozone, electrolysis and granular activated carbon (GAC) were examined as potential post-treatments to follow a household-scale biologically activated membrane bioreactor (BAMBi), treating a wash water containing trace urine and feces contamination. Each post-treatment was evaluated for abilities and reaction preferences to remove or transform dissolved organic carbon (DOC), chemical structures that contribute color, and assimilable organic carbon (AOC), which can support bacterial regrowth. Batch treatment with each technology demonstrated an ability to remove ≥95% DOC. Ozone demonstrated a reaction selectivity through increased reaction rates with larger compounds and color-contributing compounds. Electrolysis and GAC demonstrated generally less-selective reactivity. Adding post-treatments to full-scale systems reduced DOC (55–91%), AOC (34–62%), and color (75–98%), without significant reaction selectivity. These reductions in DOC and AOC were not linked to reduction of bacterial concentrations in treated water. Reductions in bacterial concentrations were observed with ozone and electrolysis, but this is credited to oxidation chemicals produced in these systems and not the removal or transformations of organic materials.
Highlights
Recycling greywater or other wastewaters for high-quality applications, such as hand washing, can dramatically reduce global demand for freshwater and enable safer water access for improved hygiene in the developing world and other challenging environments
Each post-treatment was evaluated for abilities and reaction preferences to remove or transform dissolved organic carbon (DOC), chemical structures that contribute color, and assimilable organic carbon (AOC), which can support bacterial regrowth
Reductions in bacterial concentrations were observed with ozone and electrolysis, but this is credited to oxidation chemicals produced in these systems and not the removal or transformations of organic materials
Summary
Recycling greywater or other wastewaters for high-quality applications, such as hand washing, can dramatically reduce global demand for freshwater and enable safer water access for improved hygiene in the developing world and other challenging environments This opportunity has inspired a new wave of research and development into advanced greywater and blackwater recycling systems that employ advanced process technologies to achieve improved water quality beyond what has traditionally been required for irrigation or toilet flushing (Gassie and Englehardt, 2017; Nguyen et al, 2017; Dubowski et al, 2019; Ziemba et al, 2019). For existing greywater systems that have demonstrated promising performance and economic feasibility, it may be beneficial to add a posttreatment step to achieve treatment objectives for carbon and other objectives
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