Hydrodynamics and mathematical modelling in a low HRT inverse fluidized-bed reactor for biological sulphate reduction

Advances in heavy metal removal by sulfate-reducing bacteria

Industrial development has led to generation of large volumes of wastewater containing heavy metals, which need to be removed before the wastewater is released into the environment. Chemical and electrochemical methods are traditionally applied to treat this type of wastewater. These conventional methods have several shortcomings, such as secondary pollution and cost. Bioprocesses are gradually gaining popularity because of their high selectivities, low costs, and reduced environmental pollution. Removal of heavy metals by sulfate-reducing bacteria (SRB) is an economical and effective alternative to conventional methods. The limitations of and advances in SRB activity have not been comprehensively reviewed. In this paper, recent advances from laboratory studies in heavy metal removal by SRB were reported. Firstly, the mechanism of heavy metal removal by SRB is introduced. Then, the factors affecting microbial activity and metal removal efficiency are elucidated and discussed in detail. In addition, recent advances in selection of an electron donor, enhancement of SRB activity, and improvement of SRB tolerance to heavy metals are reviewed. Furthermore, key points for future studies of the SRB process are proposed.

Effect of ammonium, electron donor and sulphate transient feeding conditions on sulphidogenesis in sequencing batch bioreactors

This work aimed to study the effect of transient feeding conditions on sulphidogenesis in 8 sequencing batch bioreactors (SBR). SBR L1 and H1, operated under steady-state conditions were used as the control reactors, while four SBR were tested under transient feeding conditions using moderate (L2 and L3, feast and famine: 2.5 and 0 g SO₄^2-·L^-1) and high (H2 and H3, feast and famine: 15 and 0 g SO₄^2-·L^-1) loads. The sulphate removal efficiency (RE) was ≥90% in SBR L2, L3 and H1. The NH₄⁺ famine conditions resulted in a higher sulphate RE (≥40% H3) compared to feast conditions (≤20% H2). Besides, the sulphidogenic first-order kinetic constant was 4% larger and the use of electron donor was 16.6% more efficient under NH₄⁺ famine conditions. Sulphidogenesis is robust to transient feeding conditions, but not when applying high loading rates (SBR H2 and H3).