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Title:	Treatment of produced water using nanofiltration and reverse osmosis membranes for potable water resources
Authors:	Salem Abdullah Mubarak Alzahrani (P53246)
Supervisor:	Abdul Wahab Mohammad, Professor Dato' Ir. Dr
Keywords:	Treatment Produced water Nanofiltration Reverse osmosis membranes Potable water resources Oil field brines
Issue Date:	8-Sep-2013
Description:	Produced water is one of the largest wastewater streams generated by the petroleum industry and totals more than 437 million barrels per day, of which 99% is disposed to the environment. Consequently, concerns relating to water resource sustainability suggest exploring the potential reuse of treated produced water (viz., produced water treated to disposal standards) as a promising source of water. To that end, this research investigated the possibility of treating produced water using new and highly hydrophilic nanofiltration (NF) and reverse osmosis (RO) membranes for reuse as indirect potable water. The study comprised comprehensive characterization of membranes, evaluation of removal efficiency performance by assessing water quality and toxicity, and studies of fouling and cleaning. It was found that the NF membrane was super hydrophilic at 23° ± 0.90°C and the RO membrane at 37°± 0.49°C. Additionally, attenuated total reflectance Fourier-transform infrared spectra indicated that the membranes had a polyethersulfone structure. The NF membrane was characterized by a smooth surface, as given by a roughness average (Ra) value of 5.06 nm and a root-mean-squared roughness of 6.39 nm, whereas the Ra value of the RO membrane was 21.7 nm and the root-mean-squared roughness was 17.2 nm. The NF membrane exhibited higher permeability 7.3 (L. m⁻². h⁻¹) than the RO membrane 3.4 (L. m⁻². h⁻¹). The flux of filtration produced water reached 75 (L. m⁻². h⁻¹) through the NF membrane and 35 (L. m⁻². h⁻¹) through the RO membrane. The rejection of 12 single salts ranged 37%-96.6% for the RO membrane and 36%-97% for the NF membrane. A total of 213 parameters of water quality were investigated. Water obtained with NF and RO membranes met 74 parameters listed in international standards of drinking water except those for molybdenum, ammonia and boron. Toxicity tests further revealed that the RO-treated produced water was free of toxicity and was therefore suitable for reuse. Conversely, the NF-treated produced water was found to be toxic at an effective concentration of 13.65% (EC50). The analysis of more than 138 parameters not regulated internationally suggested that chemical additives have a high potential to contribute toxicity to produced water treated by an NF membrane. However, the NF membrane removed 48% of total organic carbon and its application showed potential as a pretreatment for the RO membrane and in other beneficial applications. The fouling studies showed that foulants in produced water are complex and originate from 975 mg/L total dissolved solids, 26.9 mg/L total organic carbon, 42,000 cfu/mL bacteria and 10 mg/L total suspended solids. Foulants had diameters ranging from 462.8 to 653 nm and their zeta potentials ranged from -21.0 ± 4.76 to -26.6± 8.22 mV. Additionally, both biofouling and organic fouling reduced flux, and extracellular polysaccharides formed in biofilms. Foulant size affected RO membrane more than NF membrane, while the latter were more affected by pressure variations, whereas high pH mitigated flux decline in both membranes. Chemical cleaning with NaOH, sodium dodecyl sulfate (SDS) and disodium ethylenediaminetetraacetate (Na2-EDTA) was highly effective in removing easily the fouling layer from membranes; efficiencies ranged from 81.33% to 142.9%. In conclusion, converting produced water from a pollution source into a new water resource was shown to be readily achievable, especially through the use of a combined-membrane system rather than a single-membrane system.,Ph.D
Pages:	311
Call Number:	TN871.A459 2013 3
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

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