Performance of a moving bed-membrane bioreactor treating saline wastewater contaminated by hydrocarbons from washing of oil tankers

Abstract

2016): Performance of a moving bed-membrane bioreactor treating saline wastewater contaminated by hydrocarbons from washing of oil tankers, Desalination and Water Treatment, A B S T R A C TThis work analyses the performance of a moving bed-membrane bioreactor (MB-MBR) in the treatment of saline wastewater contaminated by hydrocarbons from washing of oil tankers with seawater (slops). In order to allow a biomass acclimation, a gradual increase in salinity and total petroleum hydrocarbons (TPHs) were adopted during six experimental phases. The results showed that acclimation of heterotrophic strains to TPHs occurred during Phase IV (30% by volume of slop). This is confirmed by an evident increase in the biological removal efficiencies of chemical oxygen demand, total organic carbon and TPHs. In particular, the TPHs removal efficiency increased from about 8% up to the range of 35-70%. No inhibition of the ammonia oxidizing bacteria (AOB) was noted except for Phase VI (100% by volume of slop) characterized by a collapse of ammonium removal efficiency from about 95% to about 21-24%. An accumulation of nitrite at the end of Phase IV, suggested an inhibition of nitrite-oxidizing bacteria (NOB), while a simultaneous "salt-in" of bromide indicated the acclimation of the same strains to salinity. Moreover, the hydraulic performance showed a high increase in total resistance to filtration (R T ) during the pseudostationary phases (from Phase I to Phase III) and during Phase VI, due to the high salinity and hydrocarbons concentration. The results showed that the MB-MBR system has high potentiality for the treatment of saline oily wastewater.

Characterization and Treatment Proposals of Shipboard Slop Wastewater Contaminated by Hydrocarbons

“…Regarding the biological treatment, two technologies are proposed: a membrane bioreactor (MBR) and a Moving Bed-Membrane Bioreactor (MB-MBR) characterized by the presence of soft polyurethane sponges as carrier material for biofilm growth, details can be found in [6,7]. The feeding wastewater was stored in a 150 L tank, equipped with a mechanical mixer, from which it was fed to the pilot plants.…”

“…Even though several studies have been carried out about produced water treatment [1,2,[8][9][10][11][12][13][14][15][16][17], shipboard slops wastewater treatment is a topic worthy of further investigation also in light of the lack of information and research articles regarding their treatment [5][6][7]. Among the difficulties relating to the treatment of such wastewater, the characterization is a first obstacle related to the proper nature of wastewater, rich in floating oils and emulsified phases [5], which hinds the repeatability and the reproducibility of analytical methods.…”

“…Recently, MBRs are used together with biofilm such as moving bed biofilm reactors (MBBRs) to promote biofilm growth on mobile carriers and to enhance the overall biological removal efficiencies performances [35]. The combination between MBR and MBBR systems is usually referred to as moving bed membrane bioreactor (MB-MBR) [6,7,36] and it has been proved to develop specialized bacterial consortium inside the bioreactor [37]. Based on the above, any biological system needs to be previously adapted to saline oily wastewater to obtain appreciable results.…”

“…As an alternative to chemical and physical processes, biological treatments are environmental friendly but they have to take into account the biodegradation difficulties associated both with the high salinity, that could increase the osmotic pressure leading to cell death [6,7,24,25] and recalcitrant/toxic compounds which could inhibit the metabolism of microorganisms [1,26]. Activated sludge is the usual method for treating wastewater.…”

“…Moreover, between the operations of fill and draw of crude oil from and into the oil tankers, the hulls are washed with seawater in order to remove a higher portion of hydrocarbons from the walls of the tanker. This activity produces a specific shipboard industrial wastewater named "slop", which is mainly characterized by high salinity and hydrocarbons concentration [5][6][7] . Due to its polluting characteristics, slops cannot be directly discharged to the sea.…”