Efficiency of combined process of ozone and bio-filtration in the treatment of secondary effluent

The present work was aimed at studying the efficiency of the combined process of biofiltration with ozonation to improve the quality of secondary effluent. The secondary effluent from the Dinapur Sewage Treatment Plant Varanasi, India was used in this work. The process of biofiltration with the plant species of Eichornia crassipes and Lemna minor, at a flow rate of 262 ml min−1 and plant density of 30 mg L−1 for 48 h, in combination with the process of ozonation with ozone dose of 10 mg L−1 and contact time of 5 min was applied. Results revealed that combined process was statistically most suitable for the highest degradation of physico-chemical and microbial parameters with improving BDOC value. The biofiltration process is able to remove highest percentage of toxic heavy metals from the secondary effluent without production of toxicity. This technique is highly recommendable for tropical wastewater where sewage is mixed with industrial effluents.

► This is a new work in the tropical cities, like Varanasi in India.
► The work is based on the combined process of Biofiltration and Ozone treatment of secondary effluent from the wastewater treatment plant.
► Removal efficiency of toxic heavy metals was 55–70%, organic and inorganic contents was 60–85% and microbes ranges between 98–99%.