A novel bioreactor system to purify contaminated runoff water

Water scarcity has become a global crisis and an economic burden. Environmental challenges in climate change, population growth, and urbanization have raised serious concerns for safe drinking water, food security, social stability, and public health. Current physicochemical purification techniques are costly, chemically-invasive, or ineffective. The aim of this study was to engineer an eco-friendly and cost-effective water purification system using an ex-situ bioremediation approach. The main objective was to use limestone, denitrifying bacteria, and sulfate-reducing bacteria present in the soil as natural resources. Organic compost was added as a carbon source to enhance activities of intrinsic soil bacteria. All samples were collected from mining and industrial sites in Eastern Pennsylvania. We evaluated and verified the feasibility of a novel modular bioreactor system for the effective removal of nitrate, sulfate, and heavy metals from runoff water while increasing its alkalinity. The impacts of pH and temperature on the bioremediation efficiency were evaluated, revealing ideal temperatures to be above 16°C and pH above 7. Nitrate levels dropped from 80 ppm to 0 ppm, and pH increased from 4 to above 7 consistently. Combining neutralization with bacterial bioremediation proved to have synergistic benefits within 30 minutes of treatment. Results showed a successful removal of nitrate (NO₃^-), sulfate (SO₄^2-), sulfite (SO₃^2-), Zinc (Zn), Copper (Cu), Aluminum (Al), and Lead (Pb) from contaminated wastewater. This system is a cost-effective, energy-efficient, and practical tool that opens numerous avenues for generating sustainable, portable, and fast water purification options for low-income communities. A large-scale system could be adapted for commercial or industrial purposes.