El Segundo, CA, United States
El Segundo, CA, United States

Time filter

Source Type

Sgroi M.,University of Catania | Sgroi M.,University of Arizona | Roccaro P.,University of Catania | Roccaro P.,University of Arizona | And 3 more authors.
Environmental Science and Technology | Year: 2014

Ozone doses normalized to the dissolved organic carbon concentration were applied to the primary influent, primary effluent, and secondary effluent of a wastewater treatment plant producing water destined for potable reuse. Results showed the most N-Nitrosodimethylamine (NDMA) production from primary effluent, and the recycle streams entering the primary clarifiers were identified as the main source of NDMA precursors. The degradation of aminomethylated polyacrylamide (Mannich) polymer used for sludge treatment was a significant cause of precursor occurrence. A strong correlation between NDMA formation and ammonia concentration was found suggesting an important role of ammonia oxidation on NDMA production. During ozonation tests in DI water using dimethylamine (DMA) as model precursor, the NDMA yield significantly increased in the presence of ammonia and bromide due to the formation of hydroxylamine and brominated nitrogenous oxidants. In addition, NDMA formation during ozonation of dimethylformamide (DMF), the other model precursor used in this study, occurred only in the presence of ammonia, and it was attributable to the oxidation of DMF by hydroxyl radicals. Filtered wastewater samples (0.7 μm) produced more NDMA than unfiltered samples, suggesting that ozone reacted with dissolved precursors and supporting the hypothesis of polymer degradation. Particularly, the total suspended solids content similarly affected NDMA formation and the UV absorbance decrease during ozonation due to the different ozone demand created in filtered and unfiltered samples. © 2014 American Chemical Society.


Sgroi M.,University of Catania | Sgroi M.,University of Arizona | Roccaro P.,University of Catania | Roccaro P.,University of Arizona | And 3 more authors.
Chemosphere | Year: 2016

N-Nitrosodimethylamine (NDMA) formation by ozonation was investigated in the effluents of four different wastewater treatment plants destined for alternative reuse. Very high levels of NDMA formation were observed in wastewaters from treatment plants non operating with biological nitrogen removal. Selected experiments showed that hydroxyl radical did not have a significant role in NDMA formation during ozonation of wastewater. Furthermore, ozonation of three different polymers used for water treatment, including polyDADMAC, anionic polyacrylamide, and cationic polyacrylamide, spiked in wastewater did not increase the NDMA formation. Effluent organic matter (EfOM) likely reduced the availability of ozone in water able to react with polymers and quenched the produced ·OH radicals which limited polymer degradation and subsequent NDMA production. Excellent correlations were observed between NDMA formation, UV absorbance at 254 nm, and total fluorescence reduction. These data provide evidence that UV and fluorescence surrogates could be used for monitoring and/or controlling NDMA formation during ozonation. © 2015 Elsevier Ltd.


Sgroi M.,University of Catania | Sgroi M.,University of Arizona | Roccaro P.,University of Catania | Roccaro P.,University of Arizona | And 3 more authors.
Water Research | Year: 2015

Full-scale experiments to evaluate N-nitrosodimethylamine (NDMA) formation and attenuation were performed within an advanced indirect potable reuse (IPR) treatment system, which includes, sequentially: chloramination for membrane fouling control, microfiltration (MF), reverse osmosis (RO), ultraviolet irradiation with hydrogen peroxide (UV/H2O2), final chloramination, and pH stabilization. Results of the study demonstrate that while RO does effectively remove the vast majority of NDMA precursors, RO permeate can still contain significant concentrations of NDMA precursors resulting in additional NDMA formation during chloramination. Thus, it is possible for this advanced treatment system to produce water with NDMA levels higher than regional requirements for potable applications (10ng/L). The presence of H2O2 during UV oxidation reduced NDMA photolysis efficiency and increased NDMA formation (~22ng/L) during the secondary chloramination and lime stabilization. This is likely due to formation of UV/H2O2 degradation by-products with higher NDMA formation rate than the parent compounds. However, this effect was diminished with higher UV doses. Bench-scale experiments confirmed an enhanced NDMA formation during chloramination after UV/H2O2 treatment of dimethylformamide, a compound detected in RO permeate and used as model precursor in this study. The effect of pre-ozonation for membrane fouling control on NDMA formation was also evaluated at pilot- (ozone-MF-RO) and bench-scale. Relatively large NDMA formation (117-227ng/L) occurred through ozone application that was dose dependent, whereas chloramination under typical dosages and contact times of IPR systems resulted in only a relatively small increase of NDMA (~20ng/L). Thus, this research shows that NDMA formation within a potable water reuse facility can be challenging and must be carefully evaluated and controlled. © 2014 Elsevier Ltd.


PubMed | National University of Singapore, United Water and University of Arizona
Type: | Journal: Chemosphere | Year: 2015

N-Nitrosodimethylamine (NDMA) formation by ozonation was investigated in the effluents of four different wastewater treatment plants destined for alternative reuse. Very high levels of NDMA formation were observed in wastewaters from treatment plants non operating with biological nitrogen removal. Selected experiments showed that hydroxyl radical did not have a significant role in NDMA formation during ozonation of wastewater. Furthermore, ozonation of three different polymers used for water treatment, including polyDADMAC, anionic polyacrylamide, and cationic polyacrylamide, spiked in wastewater did not increase the NDMA formation. Effluent organic matter (EfOM) likely reduced the availability of ozone in water able to react with polymers and quenched the produced OH radicals which limited polymer degradation and subsequent NDMA production. Excellent correlations were observed between NDMA formation, UV absorbance at 254 nm, and total fluorescence reduction. These data provide evidence that UV and fluorescence surrogates could be used for monitoring and/or controlling NDMA formation during ozonation.


Raczko R.F.,United Water | Dyksen J.E.,United Water | Savino C.J.,Layne Christensen
AWWA/AMTA Membrane Technology Conference and Exposition 2012 | Year: 2012

United Water has successfully used gas permeable hydrophobic membranes to remove dissolved/entrained air at two of its well supplies in Rockland County, NY. Two systems were installed, a 1,700 gpm facility and an 850 gpm facility with a considerable savings (over 50%) in capital and operating costs when compared to traditional stilling basin/repumping technology used in the past. Building on the success in removing entrained/dissolved air, United Water decided to evaluate the use of this membrane technology for removing volatile organic chemicals (VOCs) and radon from groundwater supplies. This paper will present the results of the pilot testing conducted for removing VOCs, radon and THMs. The pilot test results indicate that this technology is quite effective in removing VOCs, radon and THMs. This paper will also provide a comparison of gas permeable hydrophobic membrane technology with more conventional treatment technologies (packed tower aeration and granular activated carbon). Preliminary cost comparisons indicate that this technology is significantly more cost-effective than packed tower aeration or granular activated carbon in removing VOCs and other contaminants of concern. © 2012 American Water Works Association.


Yap R.,University of New South Wales | Holmes M.,United Water | Peirson W.,University of New South Wales | Whittaker M.,University of New South Wales | And 3 more authors.
Water Science and Technology | Year: 2012

Dissolved air flotation (DAF) incorporating filtration (DAFF) is used at the Bolivar wastewater treatment plant (WWTP) to polish lagoon effluent for reuse. Elevated algal populations are frequently experienced and can lead to increased coagulant requirements and process control issues. Streaming current detectors (SCDs) and a charge demand analyser (CDA) were used to monitor the full-scale plant. This was followed by an optimisation study using a pilot plant with a CDA. It was found that the normal operational charge demand range for DAF at Bolivar was between -46 and -40 μeq L-1. Decreasing the pH of coagulation reduced coagulant consumption and facilitated more sensitive CDA responses to changes in alum dose. © IWA Publishing 2012 Water.


Lazarova V.,Suez Environnement CIRSEE | Oelker G.,United Water | Won W.,Basin Water
Water Practice and Technology | Year: 2012

A new concept developed for the successful implementation of integrated resource management in urban and protected areas is the production of 'designer' or custom-made recycled water for various reuse purposes. The Edward C. Little Water Recycling Facility in El Segundo, California is an excellent example and the only facility in the world and the United States producing five distinct types of recycled water. This paper presents the plant design, critical milestones, water quality challenges faced and problems solved towards consistently meeting the needs of a diverse client base through delivery of a leading-edge range of custom-made recycled waters. © IWA Publishing 2012.

Loading United Water collaborators
Loading United Water collaborators