Influence of the nutrition substrate concentration on sulfate reduction in denitrifying biofilter point of use

ABSTRACT The influence of bacterial nutrition (by ethanol) on the appearance of hydrogen sulfide and colloidal sulfur in the filtrate of innovative U-shaped small-sized (point-of-use) submersible denitrifying biofilter describes in the course of its regular operation. The device intends to get drinking water from groundwater sources contaminated with nitrates, sulfates, and heavy metal ions. Colonies of denitrifying bacteria occupy an ecological niche inside the filter bed in an anoxic medium in the inlet elbow of the biofilter and reduce the concentration of nitrates below of hygienic limit at the optimal feed by ethanol. Hydrogen sulfide and colloidal sulfur produce the sulfate-reducing and sulfur bacteria. Sulfate-reducing bacteria act in an anaerobic environment in the bottom conjunction zone of the inlet and outlet elbows of the biofilter. These bacteria release hydrogen sulfide when ethanol adds to filtering water in excess compared to the dosage required for denitrification. Colonies of sulfur bacteria occupy an ecological niche in the output zone of the biofilter exit elbow and oxidise hydrogen sulfide to elemental sulfur. Sulfate reduction associated with nitrates removal can be helpful for additional water purification from admixtures of heavy and polyvalent metal ions. GRAPHICAL ABSTRACT