Sung Hee Joo

Novel technologies for reverse osmosis concentrate treatment: a review.

Global water shortages due to droughts and population growth have created increasing interest in water reuse and recycling and, concomitantly, development of effective water treatment processes. Pressured membrane processes, in particular reverse osmosis, have been adopted in water treatment industries and utilities despite the relatively high operational cost and energy consumption. However, emerging contaminants are present in reverse osmosis concentrate in higher concentrations than in the feed water, and have created challenges for treatment of the concentrate. Further, standards and guidelines for assessment and treatment of newly identified contaminants are currently lacking. Research is needed regarding the treatment and disposal of emerging contaminants of concern in reverse osmosis concentrate, in order to develop cost-effective methods for minimizing potential impacts on public health and the environment. This paper reviews treatment options for concentrate from membrane processes. Barriers to emerging treatment options are discussed and novel treatment processes are evaluated based on a literature review.

Environmental dynamics of metal oxide nanoparticles in heterogeneous systems: A review

Metal oxide nanoparticles (MNPs) have been used for many purposes including water treatment, health, cosmetics, electronics, food packaging, and even food products. As their applications continue to expand, concerns have been mounting about the environmental fate and potential health risks of the nanoparticles in the environment. Based on the latest information, this review provides an overview of the factors that affect the fate, transformation and toxicity of MNPs. Emphasis is placed on the effects of various aquatic contaminants under various environmental conditions on the transformation of metal oxides and their transport kinetics - both in homogeneous and heterogeneous systems - and the effects of contaminants on the toxicity of MNPs. The presence of existing contaminants decreases bioavailability through hetero-aggregation, sorption, and/or complexation upon an interaction with MNPs. Contaminants also influence the fate and transport of MNPs and exhibit their synergistic toxic effects that contribute to the extent of the toxicity. This review will help regulators, engineers, and scientists in this field to understand the latest development on MNPs, their interactions with aquatic contaminants as well as the environmental dynamics of their fate and transformation. The knowledge gap and future research needs are also identified, and the challenges in assessing the environmental fate and transport of nanoparticles in heterogeneous systems are discussed.

Sustainable approaches for minimizing biosolids production and maximizing reuse options in sludge management: A review.

Sludge generation during wastewater treatment is inevitable even with proper management and treatment. Yet proper handling and disposal of sludge are still challenging in terms of treatment cost, presence of recalcitrant contaminants of concern, sanitary issues, and public acceptance. Conventional disposal methods (i.e. landfilling, incineration) have created concerns in terms of legislative restrictions and community perception, incentivizing consideration of substitute sludge management options. Furthermore, with proper treatment, biosolids from sludge, rich in organic materials and nutrients, could be utilizable as fertilizer. Despite the challenges of dealing with sludge, no review has dealt with integrated source reduction and reuse as the best sustainable management practices for sludge treatment. In this review, we present two main approaches as potentially sustainable controls: (i) pretreatment for minimizing extensive sludge treatment, and (ii) recycling and reuse of residual sludge. Drawing on these approaches, we also suggest strategies for efficient pretreatment mechanisms and residual reuse, presenting ideas for prospective future research.

Effects of titanium dioxide nanoparticles derived from consumer products on the marine diatom Thalassiosira pseudonana

Increased manufacture of TiO2 nanoproducts has caused concern about the potential toxicity of these products to the environment and in public health. Identification and confirmation of the presence of TiO2 nanoparticles derived from consumer products as opposed to industrial TiO2 NPs warrant examination in exploring the significance of their release and resultant impacts on the environment. To this end, we examined the significance of the release of these particles and their toxic effect on the marine diatom algae Thalassiosira pseudonana. Our results indicate that nano-TiO2 sunscreen and toothpaste exhibit more toxicity in comparison to industrial TiO2 and inhibited the growth of the marine diatom T. pseudonana. This inhibition was proportional to the exposure time and concentrations of nano-TiO2. Our findings indicate a significant effect, and therefore, further research is warranted in evaluation and assessment of the toxicity of modified nano-TiO2 derived from consumer products and their physicochemical properties.

Advanced Treatment of Reverse Osmosis Concentrate by Integrated Activated Carbon and Iron-Activated Persulfate Oxidation

Treatment of reverse osmosis concentrate (ROC) has been complicated in terms of feasibility, cost, and most importantly, efficiency in removing contaminants. While adsorbents such as activated carbon, coal, and fly ash can remove organics, they may not be effective in removing nutrient salts that cause algae growth. Moreover, with regards to physical treatment, removing contaminants using adsorbents may not be appropriate, as toxic and non-biodegradable pollutants are not transformed or degraded into non-toxic forms. In this study, a series of processes involving adsorption using activated carbon and oxidation by hydroxyl and sulfate radicals were assessed as a means of treating ROC. The method includes treating water containing organics with an adsorbent, and adding nano-sized zero-valent iron (nZVI) to the water in the presence of oxygen, followed by the addition of persulfate, where the water is oxidized with reactive oxygen species (e.g., hydroxyl radical, peroxide, superoxide anion) produced by the addition of ZVI and persulfate radicals generated from persulfate activated by the addition of nZVI. Removal of non-biodegradable organics (as well as nitrogen and phosphorous) and nutrient salts not readily removed by conventional treatment methods can be effectively accomplished through the physical removal method described, using activated carbon, and by a chemical removal method using radical oxidation.

Influence of siloxane on the transport of ZnO nanoparticles from different release pathways in saturated sand

The production of nanomaterials (NMs) is expected to grow continuously, yet their transformation, transport, release mechanisms, and interactions with contaminants under environmental conditions remain poorly understood. Few studies have investigated the effects of contaminants on fate and transport of NMs, especially siloxanes that are widely found in products. It is hypothesized that the model contaminant, siloxane (e.g., 1,1,3,3-tetramethyldisiloxane (TMDS)) may influence the mechanisms and transport kinetics of NMs under different release pathways. Sand column experiments were carried out under two different scenarios: the release from a mixed TMDS and nano-ZnO suspension (A) and the release of nano-ZnO from sand contaminated with TMDS (B). Results show that interparticle reactions are dominant in (A) and particle-porous interactions are responsible for blocking effects governing in (B). Insights, especially the kinetics of nano-ZnO from co-transport by a contaminant and from porous media preloaded with a contaminant, and environmental factors affecting the release and retention of nano-ZnO in saturated sand are unveiled. These two dominant transport mechanisms (e.g., interparticle reactions and blocking effects) were derived. This study indicates that the release of ZnO NPs is influenced by the presence of TMDS; the extent of mobility and their transport pathways depend on the pre-existence of TMDS in porous media.

The Ecotoxicological Impact of Metal Oxide Nanoparticles on Pool Algae in the Presence and Absence of Disinfection Byproducts: a New Research Direction for the Public Health and Safety of Engineered Nanoparticles used in Consumer Products

Recent research on potential carcinogens in recreational waters has spawned public concerns about the long-term public health impacts of disinfectants used in pools. However, no attention has been given to the ecological and public health impacts of metal oxides in cosmetics and sunscreens within swimming pools where leisure activities occur. The discussion in this perspective focuses on the interaction between metal oxide nanoparticles released from swimmers into pools where algae is present, and the synergistic toxicological effects of pool algae adsorbed by metal oxide nanoparticles in the presence of disinfection byproducts in comparison to the absence of contaminants. This perspective will address research approaches to evaluating metal oxide nanoparticle impacts on pool algae, and the challenge of identifying the potential mechanisms leading to transformed algae.

Case study on pressured microfiltration and reverse osmosis membrane systems for water reuse

Abstract According to the announcement by OECD [1], Korea is listed as the most “severe water stress” nation among OECD countries. As competition for restricted water resources is expected in the coming decades, development of technologies for water treatment and reuse becomes urgently needed. The combined microfiltration (MF) and reverse osmosis (RO) process has been one of the mostly employed treatment methods in obtaining recyclable quality for wastewater reclamation and reuse, yet few has reported a pilot-scale investigation with the pressurized MF (without pretreatment) and RO system. The pilot plant operated in Gimcheon City Sewage Treatment Plant consists of a PVDF membrane in pressurized MF (treatment capacity of MF and RO: 30 and 20 m3/day) and a RO unit of wastewater reclamation. The result of the pilot study indicates that the reclaimed water can conform industrial water reuse standard (i.e., Turbidity (MF): 0.05 NTU, TDS (RO): 4.9 mg/L, TOC (RO): 0.79 mg/L). While the recovery rate run at the ...