Biohydrogen production by coupling an electrochemical system with a biological treatment

The main objective of this work was to examine the feasibility of biohydrogen production using ammonium solution resulting from nitrate electrochemical reduction. In this coupled process a concentrated nitrate solution of 3g NO
3
L
⁻¹
was firstly converted to ammonium using a home-made electrochemical flow cell, leading to 97% ammonium selectivity. This solution was then used as a nitrogen source to produce H
2
in a batch system involving heat-treated aerobic activated sludge. Under proved optimal conditions, pH 5.5 and 15g L
⁻¹
initial glucose concentration a hydrogen yield of 0.35 mol H
2
/mol glucose was obtained, with total consumption of the produced ammonium. The obtained biogas contains only H
2
and CO
2
and was free of methane, hydrogen sulphide (H2S) and nitrous oxide (N
2
O).