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Deaeration units of a commercial multi-stage flash (MSF) cogeneration facility underwent venting modifications to increase system distillate productivity without increasing energy consumption or elevating top brine temperatures. Three MSF units were investigated after oxygen levels of deaerators spiked above design limits (20 ppb). The investigation found a significant biotic presence in the deaerator unit's MSF heat rejection sections that included algae, bacteria, bivalves, and bivalve larvae. The bivalve taxa consists of Barbatia parva, Diodora funiculata, Pinctada margaritifera, Amiantis umbonella, and Acrostergma assimile. Galvanic corrosion exacerbated by biofilm was also observed in heat rejection sections. While attesting to the tenacity and adaptability of marine life, the presence of biological communities is symptomatic of the abnormally high oxygen levels in deaerator units. Elevated oxygen levels contribute to systems performance declines resulting from biological fouling of deaerator packing materials, partially responsible for inefficiencies in reducing the gas solubilities of MSF process feed waters and elevated concertation ratios [1,2]. Several thermal desalination units presented similar process issues, but one was selected for detailed inspection and evaluation. [ABSTRACT FROM AUTHOR]

Scale samples from a 144,000 m3/d Arabian Gulf multi-stage flash (MSF) desalination plant were collected and assayed for organic, biological, and inorganic compounds. Samples were collected from the bottom side of the deaerator and the first flash chamber of a 24,000 m3/d MSF unit. For the first time, organic compounds and adenosine triphosphate were characterized and identified in both selected locations. Within predominantly calcium carbonate (in the deaerator) and magnesium hydroxide (in the first stage of MSF) scale samples, organics were detected, and their potential sources suggested based on related literature. Organic compounds found are consistent with degradation components of bacterioneuston with some contribution from species present in the seawater source and pretreatment chemicals. These findings raise the possibility of a significant role of organic compounds in alkaline scale nucleation and grow th in the MSF process. [ABSTRACT FROM AUTHOR]

SWCC DTRI adopted a highly ambitious research program in which nanofiltration (NF) membranes operated on pretreated seawater to improve its scaling and fouling potential. NF membrane seawater pretreatment was introduced commercially at SWCC Umm Lujj SWRO plant, where NF and SWRO processes operated at 65% and 50% recovery, respectively, with an overall recovery of 32.5%. Therefore, this paper presents (Part-II) of this project, which deals with NF product as a superior RO feed with the main objective of increasing the water production at Umm Lujj NF/SWRO plant and improve its overall economics. In order to achieve the same, several approaches were adopted which includes long-term performance evaluation of NF membrane seawater pretreatment, SWRO and BWRO processes at recoveries of 90%, 52% and 92%, respectively. The results revealed that Umm Lujj NF/SWRO plant overall recovery can be increased from 32.5% to 44%. [ABSTRACT FROM AUTHOR]

The Saline Water Conversion Corporation (SWCC) is responsible for desalting seawater and faces several challenges, such as high feed salinity with high feed temperature and very stringent permeate quality standards (TDS < 50 mg/l, chloride <25 mg/l, and boron < 2.4 mg/l). Most plants employ hollow fiber membrane technology, with smaller plants operating at 30–35% recovery rates, whereas larger plants operate at an approximately 42% recovery rate. The SWRO permeate boron concentration is between 2 and 3 mg/l. Finally, the Umm Lujj SWRO plant employs NF pretreatment and operates at approximately 32.5% overall recovery. This study focuses on designing high recovery SWRO operations by employing spiral wound membranes and recent design approaches. The study using Gulf seawater includes a performance comparison of five different SWRO elements, an examination of the performance of conventional 6-element arrays compared to 7- and 8-element arrays, a performance comparison of 5 hybrid and non-hybrid SWRO designs and an evaluation of the performance of two hybrid SWRO designs operated at 46.5 and 48% recovery and incorporating a split partial two pass approach over 6100 hours of operation. The results indicate that spiral wound membranes with recent design approaches succeed in maximizing the overall recovery up to 45–46.5% compared with existing plants, with an overall recovery of 33–38%. [ABSTRACT FROM AUTHOR]

Membrane punch autopsy (MPA) is a procedure for quantitative foulant analysis of hollow fine fiber (HFF) permeators. In the past, quantitative autopsies of membranes were restricted to spiral wound. This procedure was developed at SWCC laboratories and tested on permeators of two commercial Red Sea reverse osmosis plants. For membrane autopsies, stainless steel hollow bore picks were penetrated to membrane cores and fibers extracted for foulant analysis. Quantitative analysis of extracted materials contained inorganic and organic foulants including bacteria. Fourier transform infrared spectroscopy analysis confirmed the presence of organic fouling functional groups and scanning electron microscopy with energy dispersive X-ray spectroscopy in the presence of diatoms and silica most likely not from particulate sand. API analysis revealed the presence of Shewanella and two Vibrio microbial species confirmed by 16S rDNA sequence library. It was observed that fouling content of HFF cellulose triacetate (CTA) membranes were more than 800 times than polyamide spiral wound membranes. [ABSTRACT FROM AUTHOR]

For providing advanced desalination the combination of the improvement of water recovery ratio in the reverse osmosis (RO) process and the No-Chlorine/No-Sodium Bisulfite (SBS) Dosing process was studied. In order to prevent membrane fouling even in high recovery water operations, an advanced two-stage design was implemented to (1) control the permeate flux through the RO membrane module, (2) optimize the system to reduce contaminant build-up and (3) eliminate the use of chlorine and SBS, which can accelerate membrane fouling. The system was evaluated by monitoring the biofouling and the microorganisms proliferation on the membrane surface based on membrane biofilm formation rate (mBFR). The pilot plant was operated in the condition of a water recovery rate of 55%. As a result, the system was operated for longer than four months without membrane cleaning (clean in place; CIP) and the possibility of operation for seven months without CIP was confirmed by the extrapolation of the pressure values. In addition, the mBFR is a reliable tool for water quality assessment, based on a comparison between the fouling tendency estimated from the mBFR and the actual membrane surface condition from autopsy study and the effectiveness No-Chlorine/No-SBS Dosing process was verified from mBFR of pretreated seawater. [ABSTRACT FROM AUTHOR]