Samer Adham

Kinetics of nitrate and perchlorate reduction in ion-exchange brine using the membrane biofilm reactor (MBfR).

Several sources of bacterial inocula were tested for their ability to reduce nitrate and perchlorate in synthetic ion-exchange spent brine (30-45 g/L) using a hydrogen-based membrane biofilm reactor (MBfR). Nitrate and perchlorate removal fluxes reached as high as 5.4 g Nm(-2)d(-1) and 5.0 g ClO(4)m(-2)d(-1), respectively, and these values are similar to values obtained with freshwater MBfRs. Nitrate and perchlorate removal fluxes decreased with increasing salinity. The nitrate fluxes were roughly first order in H(2) pressure, but roughly zero-order with nitrate concentration. Perchlorate reduction rates were higher with lower nitrate loadings, compared to high nitrate loadings; this is a sign of competition for H(2). Nitrate and perchlorate reduction rates depended strongly on the inoculum. An inoculum that was well acclimated (years) to nitrate and perchlorate gave markedly faster removal kinetics than cultures that were acclimated for only a few months. These results underscore that the most successful MBfR bioreduction of nitrate and perchlorate in ion-exchange brine demands a well-acclimated inoculum and sufficient hydrogen availability.

Peak flux performance and microbial removal by selected membrane bioreactor systems.

A pilot study was conducted over a period of 18 months at the Point Loma Wastewater Treatment Plant (PLWWTP) in San Diego, CA to evaluate the operational and water quality performance of six selected membrane bioreactor (MBR) systems at average and peak flux operation. Each of these systems was operated at peak flux for 4 h a day for six consecutive days to assess peak flux performance. Virus seeding studies were also conducted during peak flux operation to assess the capability of these systems to reject MS-2 coliphage. When operating at steady state, these MBR systems achieved an effluent BOD concentration of <2 mg/L and a turbidity of <0.1 NTU. Peak flux for the MBR systems ranged from 56 to 76 L/m2/h (liters per square meter per hour) with peaking factors in the range of 1.5-3.2. When switching from average to peak flux operation, a reversible drop of 22-32% in temperature-corrected permeability was observed for all submerged MBR systems. The percent drop in permeability increased as MLSS concentration in the membrane tank increased from 11,100 mg/L to 15,300 mg/L and was observed to be highest for the system operating at highest MLSS concentration. Such trends were not observed with an external MBR system. Each MBR system was able to sustain a 4-h-a-day peak flow for six consecutive days with only moderate membrane fouling. The membrane fouling was quantified by measuring the drop in temperature-corrected permeability. This drop ranged from 13 to 33% over six days for different submerged MBR systems. The MBR systems achieved microbial removal in the range of 5.8-6.9 logs for total coliform bacteria, >5.5 to >6.0 logs for fecal coliform bacteria and 2.6 to >3.4 logs for indigenous MS-2 coliphages. When operating at peak flux, seeded MS-2 coliphage removal ranged from 1.0 to 4.4 logs, respectively. The higher log removal values (LRVs) for indigenous MS-2 coliphage among different MBR systems were probably the result of particle association of indigenous coliphage. Differences in membrane pore size (0.04-0.2 microm) amongst the MBR systems evaluated did not have a substantial impact on indigenous MS-2 coliphage removal, but seeded MS-2 coliphage removal varied among the different MBR systems.

Monitoring the integrity of reverse osmosis membranes

Several methods for monitoring the reverse osmosis (RO) membrane integrity were evaluated at a pilot-scale. These methods were classified as direct or indirect monitoring methods. The vacuum test was found to be a very promising direct monitoring method as it correlated well with virus rejection by the RO membranes. From the indirect real-time monitoring methods, On-line TOC monitoring was found to be more sensitive than on-line particle counting and conductivity monitoring. The use of more than one technique may be necessary to assure reliable operation of the membrane system.

Ensuring water re-use projects succeed — institutional and technical issues for treated wastewater re-use

The increasing need for water in the arid areas of the world has resulted in the emergence of new water re-use technologies. The success of water re-use projects however, does not just depend on the effectiveness and suitability of the technology, but also on the presence of an institutional framework that ensures that the treated water can be distributed and used safely and efficiently. These two diverse issues were examined by MWH in projects carried out in Egypt and in the USA. One project in the East Bank of Cairo assessed the potential benefits of treated wastewater for irrigation in agricultural schemes. The project established a lack of clarity on ownership and management of the treated wastewater and outlined the institutional development and legislation necessary for the safe and controlled re-use of treated wastewater. The project demonstrated enhanced crop yields but that additional treatment of the wastewater was required to improve its microbiological quality to the standards required by both international and Egyptian legislation for safe re-use. Another project carried out in California, USA assessed the new technology of submerged membrane bioreactors (MBRs) for water re-use. MBRs combine activated sludge treatment with a membrane separation process. The project studied two commercially available submerged MBR systems at pilot scale. The project was designed to evaluate the feasibility of using permeate from the MBRs treating municipal wastewater as a feed source for thin film composite reverse osmosis (RO) membranes. The MBRs were examined in both nitrification and denitrification mode and both MBR systems showed good removal of BOD, TOC and microorganisms. They both produced a high quality effluent that could be used by the RO membranes for water re-use.

Water repurification via reverse osmosis

The City of San Diego in California, United States, (City) is developing new water sources to serve its arid region. Water repurification, in which reclaimed water receives additional advanced water treatment (AWT) prior to its discharge to a potable water supply reservoir, is one of the encouraging alternatives being implemented by the City to reduce the regions reliance on less dependable imported water. The City adopted the reverse osmosis (RO) process as the foundation for the AWT because RO has been shown to accomplish the best overall removal of organics, trace metals and total dissolved solids. In addition, RO has the potential for removal of all classes of pathogens. The California Department of Health Services (DHS) issued a conditional approval of the San Diego Water Repurification project in August, 1994. Several of the comments in the DHS conditional approval letter addressed the disinfection strategy and the reliability of the membrane processes in the AWT train. In response to the DHS comments, the City of San Diego initiated a major pilot testing program to evaluate the performance of various prequalified pretreatment and RO membranes. This program was initiated in 1995 and is still ongoing. Pursuant to the work performed at the Aqua2000 Research Center the DHS issued a letter on March 4, 1998, approving the Water Repurification System. The results of these studies demonstrated RO is a very effective and reliable process for water repurification. Minimal membrane fouling was observed for all of the polyamide RO membranes employed in the study. Significant contaminant rejection was achieved by all RO membrane purifying the reclaimed water to meet and exceed drinking water standards. Wide range of virus rejection was observed for the RO membranes which was dependent on the RO membrane type/manufacturer. The system consistently produces a product water that exceeds all drinking water standards.

Using Advanced Water Treatment Technologies To Treat Produced Water From The Petroleum Industry

Produced Water (PW) is the water trapped in underground formations that is brought to the surface along with oil or gas in extraction operations and it is the highest volume liquid waste stream generated by the petroleum industry. Historically, the treatment of PW has been limited to free oil and suspended solids removal and subsequent discharge into water bodies or deep injection in disposal wells. Only a small fraction of the PW is currently being treated to an extent that allows it to be recycled & reused. However, due to any of a variety of factors including legislation, geological restrictions and local water scarcity, the future will require a greater fraction of the PW to be extensively treated and ultimately recycled & reused. The petroleum industry will have to change how it has historically been managing PW and start to consider PW as a “by-product” of strategic importance and value and not as an operational liability. This paper focuses on the application of Advanced Water Treatment Technologies (AWTTs) for the treatment of PW. The specific technologies presented include direct membrane filtration, biological treatment in membrane-bioreactors (MBRs), thermal evaporators and advanced oxidation processes (AOPs). In addition to describing their respective advantages and disadvantages, this paper also presents examples of case studies where PW is being treated and recycled & reused through the application of AWTTs in full scale facilities. This paper also presents a brief overview of a laboratory investigation carried out by ConocoPhillips GWSC, where various treatment processes (membrane filtration, biological degradation, membrane distillation (MD) and ozonation) were evaluated as PW treatment methods. The case studies reported demonstrate that thermal evaporators and membrane filtration technologies have been proven at various installations to be cost-effective at the full-scale for PW treatment. Data reported in this paper also reveal that PW can be successfully biodegraded or chemically oxidized and hence processes such as MBRs and AOPs, which have been successful in other industries but overlooked by the petroleum industry, will need to be considered. In the long term, hybrid technologies such as MD may also become a cost-effective alternative to treat PW.

Assessing the Biotreatability of Produced Water From a Qatari Gas Field

Reuse of significant quantities of produced water (PW) extracted during gasfield operations requires treatment to remove both organic and inorganic materials. Biological treatment is generally regarded as the most cost-effective method for organics removal. For industrial waste waters, biotreatment faces distinct challenges because the PW composition can dramatically affect sludge settleability, a critical parameter in the operation of conventional biotreatment systems. Membrane bioreactors (MBRs) have an inherent advantage and have proved to be successful in the treatment of industrial waste waters because a membrane filter is used to separate the treated water from the sludge rather than separation being contingent on biomass settleability. The outcomes of a bench-scale experimental study on the application of an MBR to the biotreatment of PW from Qatari gas fields are presented for three operating parameters: hydraulicretention time of 16 to 32 hours, solids-residence time of 60 to 120 days, and temperature of 22 to 38 C. The impact on chemical-oxygen-demand (COD) removal was evaluated through experimental testing by use of three parallel bench-scale MBRs. Low sludge concentrations (0.3–1.5 g/L of volatile suspended solids) were attained throughout, with instantaneous-flux values ranging from 3 to 15 L/(m h). Results indicated that the COD removal averaged 60% (54–63%), approximately one-third of this value being attributed to physical removal, with the operating parameter values shown to have no statistically significant effect on removal. Although trends were consistent with some previously reported studies performed on refinery waste water, overall removals were lower than expected. The pH of the bioreactor sludge ranged from 4.9 to 6.0, averaging 5.2, compared with a feedwater pH of 4.3, possibly contributing to the low carbon removal recorded. Adjustment of the feed pH to more than 6.5 caused a precipitate to form that contributed to membrane fouling. However, all feedwater acetate and more than 90% of the oil and grease were removed by the MBR treatment. Treatment appeared to be carbon-limited, accounting both for the absence of nitrification (with all removed organic nitrogen apparently being assimilated into the sludge) and for the low sludge-solids concentrations attained. Evidence suggests the feedwater contains a significant fraction (approximately 40%) of highly recalcitrant organic compounds presumed to be nitrogencontaining field chemicals (e.g., scale inhibitors and corrosion inhibitors).

Occurrence and removal of microbial indicators from municipal wastewaters by nine different MBR systems

Nine different membrane bioreactor (MBR) systems with different process configurations (submerged and external), membrane geometries (hollow-fiber, flat-sheet, and tubular), membrane materials (polyethersulfone (PES), polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (PTFE)) and membrane nominal pore sizes (0.03-0.2 μm) were evaluated to assess the impact of influent microbial concentration, membrane pore size and membrane material and geometries on removal of microbial indicators by MBR technology. The log removal values (LRVs) for microbial indicators increased as the influent concentrations increased. Among the wide range of MBR systems evaluated, the total and fecal coliform bacteria and indigenous MS-2 coliphage were detected in 32, 9 and 15% of the samples, respectively; the 50th percentile LRVs were measured at 6.6, 5.9 and 4.5 logs, respectively. The nominal pore sizes of the membranes, membrane materials and geometries did not show a strong correlation with the LRVs.

Treatment of Produced Water from Unconventional Resources by Membrane Distillation

Unconventional resources (Shale gas/oil) use significant volumes of water for hydraulic fracturing (fracking). While some of the water used is fresh groundwater, there are more environmental pressures to use brackish water sources for fracking. This brackish water may need to be treated to lower the saturation levels and to allow mixing of field chemicals. Unconventional resources also produced high volume of flow-back water (produced water). This produced water (PW) contains high levels of total dissolved solids (TDS) and desalination may be needed to allow recycling or reuse of this water source. Membrane Distillation (MD) is an innovative process that can desalinate highly saline waters (30,000–100,000 mg/L TDS) more effectively than reverse osmosis. As a proof of concept, bench-scale MD testing were performed on brackish and produced water samples (30,000 mg/L-60,000 mg/L TDS) obtained from Texas. Results have shown excellent TDS rejection (99.9 %) on all the water samples that were tested without impacting membrane’s flux performance. To evaluate the O&M and scale up issues, two one m3/day MD pilot units are currently operating side by side at a local desalination plant in Doha. Brine from the thermal desalination plant was used as representative high salinity water (70,000 mg/L), similar salinity levels could be found in brackish groundwater and/or flow-back water. It was assumed that all other contaminants that could cause membrane fouling (such as suspended oil, solids, organics, microorganisms) will be removed in a pretreatment step prior to MD. Preliminary results showed that the pilot units were successful in completely removing salt. Flux was very stable for more than 2 weeks. However, it was concluded that pretreatment is critical for stable performance of the MD units. This presentation will provide up to date data on MD bench and pilot-scale performance with O&M issues and projected cost estimates.

Advanced Technologies For Produced Water Treatment And Reuse

Produced Water (PW) is the highest volume liquid waste stream generated by the petroleum industry. Historically, the treatment of PW has been limited to free oil and suspended solids removal, using physical separation technologies, and injection in disposal wells. However, because of new regulations combined with geological restrictions and local water scarcity, the drive to have a greater fraction of the PW more extensively treated and ultimately reused is increasing. Moreover, the growth in the application of water intensive processes to extract unconventional oil&gas resources, in particular in shale plays and oil sands, has increased the need for cost-effective treatment and reuse of PW to reduce fresh water uptakes. Therefore, the petroleum industry is investigating new PW treatment technologies given that the physical separation technologies traditionally used in the past are, in most cases, not capable of producing water of suitable quality to replace fresh water uptakes. This paper presents the results of a laboratory investigation carried out by the ConocoPhillips Global Water Sustainability Center (GWSC), where various treatment processes (membrane processes, membrane-bioreactors (MBRs), membrane distillation (MD) and ozonation) were evaluated as treatment methods for PW from different oil&gas fields. The key conclusions of this paper are: • Membrane Processes and Thermal Evaporators are currently operating within the petroleum industry in full scale PW treatment and reuse applications. • The preliminary results of investigations performed by GWSC confirmed the potential of Membrane Filtration, MBRs and Ozonation to treat PW and produce an effluent suitable for reuse. Membrane Distillation may have potential in the longer term. Further investigation is ongoing. • If successfully implemented, the above technologies will contribute to provide the petroleum industry with a broad range of technologies to cost-effectively treat and reuse PW.