Forecasting the effect of feast and famine conditions on biological sulphate reduction in an anaerobic inverse fluidized bed reactor using artificial neural networks

A critical review of inverse fluidized bed reactors-start-up optimization strategies and wastewater treatment

A critical evaluation of strategies used for reducing start-up time and biological wastewater treatment using an inverse fluidized bed reactor (IFBR) was done. The start-up of an IFBR is one of the most important, time-consuming, and limiting steps in wastewater treatment using biofilm reactors. Evaluation of different strategies used by various researchers is helpful in future research works with this reactor. Different types of treated wastewater, the effect of wastewater characteristics, carriers used, and reactor hydrodynamics on the reactor performance were reviewed in detail in the first part. The second part of this review covers the use of an IFBR in the biological treatment of different wastewaters through multiple biochemical pathways and how it helped improve performance compared to other reactors. This will enable the researchers to understand the novelty of an IFBR for wastewater treatment and allow them to use it as a potential reactor.

Evaluation of the start-up of hydraulic conditions of a fluidised bed system

The development of this research was based on the analysis of an anaerobic fluidised bed reactor from the assembly of its components to the sealing of the system and further fluidisation. A hydrometer and a Venturi were used to identify the best means of measuring the flow rate. Results produced by both devices were similar, however, the latter was less effective due to the low flow rates necessary to operate the system. The hydrometer was the most adequate device for flow rate measurements in the range between 0.1 and 1.0 m³/h, whereas the Venturi proved to be an adequate device for the flow in the range between 0.3 and 0.7 m³/h. Sand with grain sizes varying from 357 to 1000 µm was used as support material. It was not observed statistically significant differences between the minimum fluidisation velocities related to the amount of supported material of 20% and 40% (V_SM/V_usable) added to the reactor. Forty percent of the usable volume occupied with sand is adequate to reach fluidisation, instead of only the expansion of the bed. The fluidisation velocities for the sand grain size of 357 µm were 8.4 m/h ± 0.25 for 20%, and 8.6 m/h ± 0.30 for 40%, whereas for the 505 µm they were, respectively for 20% and 40%, 9.2 m/h ±0.70 and 10.1 m/h ± 0.37. The hydraulic tests allow to stress that sand grain sizes varying from 357 to 505 µm are recommended to be used in a system with similar characteristics.

Simultaneous sulfamethoxazole biodegradation and nitrogen conversion by Achromobacter sp. JL9 using with different carbon and nitrogen sources

This study investigated sulfamethoxazole (SMX) biodegradation and nitrogen conversion by Achromobacter sp. JL9 using different carbon and nitrogen sources. Results showed that SMX and sodium acetate could be co-metabolized as carbon sources for bacterial growth and nitrogen conversion with highest removal efficiencies of 82.44%, 80.2%, and 79.45% for NH₄⁺-N, NO₃^--N, and SMX, respectively. Strain JL9 was able to utilize SMX as its sole nitrogen source for growth, with an SMX biodegradation efficiency of 63.10%. In addition, carbon and nitrogen balance analyses showed that approximately 35.31% and 63.22% of carbon and nitrogen, respectively, were lost as gaseous products. Finally, medium toxicity gradually decreased during the carbon and nitrogen dependence experiments. This study, thus, suggests that carbon and nitrogen play vital roles in SMX biodegradation and biotoxicity reduction.

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).