Coagulation-flocculation and moving bed biofilm reactor as pre-treatment for water recycling in the petrochemical industry.

Water recycling and reuse is of important value in water-using sectors like petrochemical industry. The aim of this research was to optimise the pre-treatment of petrochemical wastewater to undergo a further membrane treatment, with the final objective of water recycling within the same industry. Laboratory coagulation-flocculation tests prior to biological treatment were performed using Actiflo® Veolia commercial technology and an optimal coagulant dose of 30 mg/L ferric chloride was obtained. A bench-scale Moving Bed Biofilm Reactor (MBBR) system with two sequential reactors with working volumes of 5 L was filled with Z-carriers at 35% of their working volume. Organic loading rate (OLR) was varied from 0.2 to 3.25 kg/(m3 d) and the hydraulic retention time (HRT) ranged from 23.4 h to 4.5 h. High soluble chemical oxygen demand (sCOD) removals were obtained in stationary states (80-90%) and the calculated maximum sCOD that the system could degrade was 4.96 ±â€¯0.01 kg/(m3 d) at 23 ±â€¯2 °C. Changes in feed composition did not decrease sCOD removals showing that MBBR is a robust technology and the coagulation-flocculation step could be by-passed. Further removal of total suspended solids (TSS) and turbidity from the MBBR effluent would be required before a reverse osmosis (RO) step could be performed. A biofilm-forming genus, Haliscomenobacter spp., and an oil degrading genus Flavobacterium spp. were found in all the attached biomass samples. Acinetobacter spp. was the major bacterial genera found in suspended biomass. Proteobacteria and Bacteroidetes were the major phyla detected in the carrier samples while Proteobacteria the main one detected in the suspended biomass. The lack of fungal annotated sequences in databases led to a major proportion of fungal sequences being categorized as unclassified Fungi. The results obtained indicate that MBBR is an appropriate technology for hydrocarbon-degrading microorganism growth and, thus, for petrochemical wastewater pre-treatment for water regeneration.

Biological support media influence the bacterial biofouling community in reverse osmosis water reclamation demonstration plants.

The diversity of the bacterial community developed in different stages of two reverse osmosis (RO) water reclamation demonstration plants designed in a wastewater treatment plant (WWTP) in Tarragona (Spain) was characterized by applying 454-pyrosequencing of the 16S rRNA gene. The plants were fed by secondary treated effluent to a conventional pretreatment train prior to the two-pass RO system. Plants differed in the material used in the filtration process, which was sand in one demonstration plant and Scandinavian schists in the second plant. The results showed the presence of a highly diverse and complex community in the biofilms, mainly composed of members of the Betaproteobacteria and Bacteroidetes in all stages, with the presence of some typical wastewater bacteria, suggesting a feed water origin. Community similarities analyses revealed that samples clustered according to filter type, highlighting the critical influence of the biological supporting medium in biofilm community structure.