Joseph G. Jacangelo

Emerging desalination technologies for water treatment: a critical review.

In this paper, a review of emerging desalination technologies is presented. Several technologies for desalination of municipal and industrial wastewater have been proposed and evaluated, but only certain technologies have been commercialized or are close to commercialization. This review consists of membrane-based, thermal-based and alternative technologies. Membranes based on incorporation of nanoparticles, carbon nanotubes or graphene-based ones show promise as innovative desalination technologies with superior performance in terms of water permeability and salt rejection. However, only nanocomposite membranes have been commercialized while others are still under fundamental developmental stages. Among the thermal-based technologies, membrane distillation and adsorption desalination show the most promise for enhanced performance with the availability of a waste heat source. Several alternative technologies have also been developed recently; those based on capacitive deionization have shown considerable improvements in their salt removal capacity and feed water recovery. In the same category, microbial desalination cells have been shown to desalinate high salinity water without any external energy source, but to date, scale up of the process has not been methodically evaluated. In this paper, advantages and drawbacks of each technology is discussed along with a comparison of performance, water quality and energy consumption.

Chlorine inactivation of adenovirus type 40 and feline calicivirus.

ABSTRACT Ct values, the concentration of free chlorine multiplied by time of contact with virus, were determined for free-chlorine inactivation experiments carried out with chloroform-extracted (dispersed) and non-chloroform-extracted (aggregated) feline calicivirus (FCV), adenovirus type 40 (AD40), and polio virus type 1 (PV-1). Experiments were carried out with high and low pH and temperature conditions. Ct values were calculated directly from bench-scale free-chlorine inactivation experiments and from application of the efficiency factor Hom model. For each experimental condition, Ct values were higher at pH 8 than at pH 6, higher at 5°C than at 15°C, and higher for dispersed AD40 (dAD40) than for dispersed FCV (dFCV). dFCV and dAD40 were more sensitive to free chlorine than dispersed PV-1 (dPV-1). Cts for 2 log inactivation of aggregated FCV (aFCV) and aggregated PV-1 (aPV-1) were 31.0 and 2.8 orders of magnitude higher than those calculated from experiments carried out with dispersed virus. Cts for 2 log inactivation of dFCV and dAD40 in treated groundwater at 15°C were 1.2 and 13.7 times greater than in buffered-demand-free (BDF) water experiments at 5°C. Ct values listed in the U.S. Environmental Protection Agency (EPA) Guidance Manual were close to, or lower than, Ct values generated for experiments conducted with dispersed and aggregated viruses suspended in BDF water and for dispersed viruses suspended in treated groundwater. Since the state of viruses in water is most likely to be aggregated and associated with organic or inorganic matter, reevaluation of the EPA Guidance Manual Ct values is necessary, since they would not be useful for ensuring inactivation of viruses in these states. Under the tested conditions, dAD40, dFCV, aFCV, dPV-1, and aPV-1 particles would be inactivated by commonly used free chlorine concentrations (1 mg/liter) and contact times (60 to 237 min) applied for drinking water treatment in the United States.

Energy minimization strategies and renewable energy utilization for desalination: A review

Energy is a significant cost in the economics of desalinating waters, but water scarcity is driving the rapid expansion in global installed capacity of desalination facilities. Conventional fossil fuels have been utilized as their main energy source, but recent concerns over greenhouse gas (GHG) emissions have promoted global development and implementation of energy minimization strategies and cleaner energy supplies. In this paper, a comprehensive review of energy minimization strategies for membrane-based desalination processes and utilization of lower GHG emission renewable energy resources is presented. The review covers the utilization of energy efficient design, high efficiency pumping, energy recovery devices, advanced membrane materials (nanocomposite, nanotube, and biomimetic), innovative technologies (forward osmosis, ion concentration polarization, and capacitive deionization), and renewable energy resources (solar, wind, and geothermal). Utilization of energy efficient design combined with high efficiency pumping and energy recovery devices have proven effective in full-scale applications. Integration of advanced membrane materials and innovative technologies for desalination show promise but lack long-term operational data. Implementation of renewable energy resources depends upon geography-specific abundance, a feasible means of handling renewable energy power intermittency, and solving technological and economic scale-up and permitting issues.

Occurrence and suitability of sucralose as an indicator compound of wastewater loading to surface waters in urbanized regions.

Urban watersheds are susceptible to numerous pollutant sources and the identification of source-specific indicators can provide a beneficial tool in the identification and control of input loads, often times needed for a water body to achieve designated beneficial uses. Differentiation of wastewater flows from other urban wet weather flows is needed in order to more adequately address such environmental concerns as water body nutrient impairment and potable source water contamination. Anthropogenic compounds previously suggested as potential wastewater indicators include caffeine, carbamazepine, N,N-diethyl-meta-toluamide (DEET), gemfibrozil, primidone, sulfamethoxazole, and TCEP. This paper compares the suitability of a variety of anthropogenic compounds to sucralose, an artificial sweetener, as wastewater indicators by examining occurrence data for 85 trace organic compounds in samples of wastewater effluents, source waters with known wastewater point source inputs, and sources without known wastewater point source inputs. The findings statistically demonstrate the superior performance of sucralose as a potential indicator of domestic wastewater input in the U.S. While several compounds were detected in all of the wastewater effluent samples, only sucralose was consistently detected in the source waters with known wastewater discharges, absent in the sources without wastewater influence, and consistently present in septic samples. All of the other compounds were prone to either false negatives or false positives in the environment.

Role of membrane technology in drinking water treatment in the United States

With the increase in water quality regulations and decrease in available fresh water supplies in the US, pressure-driven membrane processes are playing an increasingly important role in drinking water treatment. They are being employed to remove a wide range of contaminants, and depending on their use, can be operated with minimal or no chemical pretreatment that forms deleterious by-products. The major uses of membrane processes in the US include desalting, disinfection by-product control, disinfection, clarification and removal of synthetic and inorganic chemicals. Membranes are also furthering capabilities to purify wastewater for indirect potable reuse.

Inactivation of enteric adenovirus and feline calicivirus by chlorine dioxide

ABSTRACT Chlorine dioxide (ClO2) inactivation experiments were conducted with adenovirus type 40 (AD40) and feline calicivirus (FCV). Experiments were carried out in buffered, disinfectant demand-free water under high- and low-pH and -temperature conditions. Ct values (the concentration of ClO2 multiplied by contact time with the virus) were calculated directly from bench-scale experiments and from application of the efficiency factor Hom (EFH) model. AD40 Ct ranges for 4-log inactivation (Ct99.99%) at 5°C were >0.77 to <1.53 mg/liter × min and >0.80 to <1.59 mg/liter × min for pH 6 and 8, respectively. For 15°C AD40 experiments, >0.49 to <0.74 mg/liter × min and <0.12 mg/liter × min Ct99.99% ranges were observed for pH 6 and 8, respectively. FCV Ct99.99% ranges for 5°C experiments were >20.20 to <30.30 mg/liter × min and >0.68 mg/liter × min for pH 6 and 8, respectively. For 15°C FCV experiments, Ct99.99% ranges were >4.20 to <6.72 and <0.18 mg/liter × min for pH 6 and 8, respectively. Viral inactivation was higher at pH 8 than at pH 6 and at 15°C than at 5°C. Comparison of Ct values and inactivation curves demonstrated that the EFH model described bench-scale experiment data very well. Observed bench-scale Ct99.99% ranges and EFH model Ct99.99% values demonstrated that FCV is more resistant to ClO2 than AD40 for the conditions studied. U.S. Environmental Protection Agency guidance manual Ct99.99% values are higher than Ct99.99% values calculated from bench-scale experiments and from EFH model application.

Sources of nutrients impacting surface waters in Florida: A review

The promulgation of numeric nutrient criteria for evaluating impairment of waterbodies in Florida is underway. Adherence to the water quality standards needed to meet these criteria will potentially require substantial allocations of public and private resources in order to better control nutrient (i.e., nitrogen and phosphorus) releases from contributing sources. Major sources of nutrients include atmospheric deposition (195-380 mg-N/m(2)/yr, 6 to 16 mg-P/m(2)/yr), reclaimed water irrigation (0.13-29 mg-N/L, 0.02 to 6 mg-P/L), septic systems (3.3 × 10(3)-6.68 × 10(3) g-N/person/yr, 0.49 × 10(3)-0.85 × 10(3) g-P/person/yr) and fertilizer applications (8 × 10(6)-24 × 10(6) mg-N/m(2)/yr). Estimated nitrogen loadings to the Florida environment, as calculated from the above rates are as follows: 5.9 × 10(9)-9.4 × 10(9) g-N/yr from atmospheric deposition, 1.2 × 10(8)-2.6 × 10(10) g-N/yr from reclaimed water, 2.4 × 10(10)-4.9 × 10(10) g-N/year from septic systems, and 1.4 × 10(11) g-N/yr from fertilizer application. Similarly, source specific phosphorus loading calculations are also presented in this paper. A fraction of those nutrient inputs may reach receiving waterbodies depending upon site specific regulation on nutrient control, nutrient management practices, and environmental attenuation. In Florida, the interconnectivity of hydrologic pathways due to the karst landscape and high volumes of rainfall add to the complexity of tracking nutrient loads back to their sources. In addition to source specific nutrient loadings, this review discusses the merits of source specific markers such as elemental isotopes (boron, nitrogen, oxygen, strontium, uranium and carbon) and trace organic compounds (sucralose, gadolinium anomaly, carbamazepine, and galaxolide) in relating nutrient loads back to sources of origin. Although this review is focused in Florida, the development of source specific markers as a tool for tracing nutrient loadings back to sources of origin is applicable and of value to all other geographical locations.

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.

Effects of magnetic ion exchange pretreatment on low pressure membrane filtration of natural surface water

Magnetic ion exchange (MIEX) pretreatment has been increasingly employed by water treatment plants for removal of dissolved organic carbon (DOC). In this study, the effects of MIEX pretreatment on low pressure membrane filtration of natural surface water were investigated under different feedwater qualities, membrane properties, and MIEX dosing conditions. Regardless of feedwater DOC, moderate decrease in the total and hydraulically irreversible fouling was observed for a polyvinylidene fluoride (PVDF) microfiltration membrane and a polyethersulfone ultrafiltration (UF) membrane after MIEX pretreatment, which was coincident with moderate removals of high molecular weight DOC in the feedwaters. Comparatively, the fouling of a PVDF UF membrane did not decrease after MIEX pretreatment, revealing the impact of membrane properties on membrane fouling in the presence of MIEX pretreatment. Reuse of virgin or regenerated MIEX resulted in similar membrane fouling as observed with single use of the virgin MIEX. The level of DOC removal by MIEX was similar to the removal of MS2 bacteriophage spiked in the feedwater, suggesting a potential similarity in the removal of organic and microbial particles. In conclusion, MIEX pretreatment was effective for DOC removal, but less effective in controlling short-term membrane fouling or removing viruses.

Mechanisms of Membrane Fouling Control by Integrated Magnetic Ion Exchange and Coagulation

Colloidal natural organic matter (NOM) is an important foulant to low-pressure membranes (LPMs) employed in drinking water treatment. Removal of colloidal NOM by magnetic ion exchange (MIEX), coagulation, and integrated MIEX and coagulation was investigated in this study to determine the relationship between colloidal NOM removal and membrane fouling reduction. The results showed that coagulation did not selectively remove colloidal NOM and the optimal coagulant dose was primarily determined by the concentration of humic substances. Comparatively, MIEX pretreatment preferentially removed humic substances and reduced the coagulant dose needed for colloidal NOM removal as a result of coagulation stoichiometry. A matched-pair analysis showed that integrated MIEX and coagulation pretreatment at much lower coagulant doses was as effective as coagulation in reducing membrane fouling. It is concluded that integrated MIEX and coagulation is potentially a viable pretreatment approach to reduce membrane fouling and in general removal of colloidal NOM in feedwater is an effective approach for membrane fouling control and should be considered in the research, development, and application of novel LPM-based treatment processes.