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This study evaluated the performance of aluminum and iron plate electrode systems on the continuous electrocoagulation of boron from produced water under varying conditions of retention time, initial concentration and electrode distance. The experimental data were validated for mass transfer resistance using the modified mass transfer factor (MMTF) model. Results show a similar trend for both electrode systems. Boron removal decreased from 78.7–60% for aluminum electrode and 67.3–53.3% for iron electrode with shortening retention time from 45 to 30 min.. Boron removal further decreased from 84 to 72.7 % for aluminum electrode and 76 to 61.3 % for iron electrode with increasing electrode distance from 0.5 cm to 1.5 cm. Analyses of the mass transfer resistance showed that the driving force (B) for boron mass transfer was concentration dependent and increased from 0.1037 to 0.4002 mg.g for aluminum electrode and 0.0445 to 0.1258 mg.g for iron electrode with increasing initial boron concentration from 5 to 15 mg/L. A similar trend was observed for the affinity between boron and the electroactive species. Analyses of boron mass transfer resistance related to the global and film mass transfer, and porous diffusion show that boron mass transfer resistance correlated to the film mass transfer for both electrode systems. Aluminum electrode system showed better performance for boron removal and higher mass transfer kinetics. This study clearly demonstrates that continuous electrocoagulation is a suitable alternative for boron removal from produced water.

The fundamental understanding of mass transfer kinetics is essential for biosorption of phosphorus by aerobic granular sludge (AGS) to gain an insight into biological processes regarding the treatment of wastewater with high organic load. The removal of phosphorus by AGS from palm oil mill effluent was performed in a sequencing batch reactor (SBR) while the experimental data were assessed using the modified mass transfer factor (MMTF) models to get better understanding on the mechanisms of external and internal mass transfer. A zigzag pattern of the [kLa]g, [kLa]f and [kLa]d variations was verified before and after addition of Serratia marcescens SA30 due to the variations of organic loading rate and total phosphorus concentration were observed at every additional 50% new sample into the SBR. This study verified that the biosorption process is controlled by transport of phosphorus through a film of external fitting AGS. The analysis of SBR performance shows a logarithmic increase in the efficiency of phosphorus removal with increasing of the [kLa]g value. A new insight of the dynamic AGS growth of biological process revealed by the MMTF models may contribute to the advanced treatment of high organic content wastewater.

An integrated hybrid bioreactor (IHB) and integrated suspended bioreactor (ISB) coupling aerobic, anoxic and settling units was evaluated for industrial wastewater treatment with and without the installation of a rectangular hollow engraved submerged Perspex media in the aerobic unit. Bioreactor performance was examined at different overall hydraulic retention times of 36, 12, 7.2, 5.1 and 4 days, respectively. Nitrogen mass balance was analyzed to examine the inhibitory effects of metabolic by-products on nitrification in IHB. Both bioreactors exhibited a short start-up period during acclimatization. Results show a lower effluent COD concentration of 15–85 mg/L in IHB and 38.6–124 mg/L in ISB. Effluent ammonia-nitrogen was 0.65–3.5 mg/L in IHB and 0.3–4.5 mg/L in ISB. Effluent nitrate and nitrite were low in both bioreactors but lower in IHB. Mass balance analysis in IHB indicated that nitrate was the dominant ammonia metabolite and decreased with reducing HRT. Microfauna investigation showed that free swimmers, crawling and attached ciliates were major protozoans in IHB while free swimmers and attached ciliates were dominant protozoans in ISB. Kinetic evaluation demonstrates that microbial growth was higher in IHB. The Y, kd, μmax and Ks for IHB was 0.1 g VSS/g COD, 0.02 per day, 0.81 per day and 1.26 g/m3 with a correlation coefficient (R2) of 0.978 while it was 0.118 g VSS/g COD, 0.04 per day, 0.635 per day and 3.93 g/m3 with a correlation coefficient (R2) of 0.988 in ISB. This study demonstrates that while both ISB and IHB were effective for industrial wastewater treatment, IHB performance was comparatively higher due to the inclusion of the submerged media.