Assessment of 265-nm UV-LED for direct photolysis and advanced oxidation of N-nitrosamines and 1,4-dioxane

The advanced oxidation process (AOP), using conventional low-pressure mercury (LP Hg)-vapor UV lamps, forms a critical barrier for pathogens and contaminants of emerging concern (CECs) in potable water reuse. In recent years, UV-light-emitting diode (UV-LED) has attracted considerable attention as an alternative UV source because it has a long lifetime and is mercury-free. This study assesses the effectiveness of 265-nm UV-LED in removal of characteristic CECs, 1,4-dioxane (100 μg/L) and N-nitrosamines (500 ng/L), including N-nitrosodimethylamine (NDMA), in recycled potable water. Direct photolysis using a UV-LED lamp, at the maximum UV dose of 900 mJ/cm2, achieved a maximum of 31% NDMA reduction, as opposed to a 93% reduction by a conventional LP Hg UV lamp. We attributed this to the longer emission wavelength of the UV-LED (265 nm) than that for the LP Hg UV lamp (254 nm). Both UV lamps failed to photolyze 1,4-dioxane. Using hydrogen peroxide or monochloramine remarkably enhanced the effectiveness of the LP Hg UV-based AOP in removing 1,4-dioxane, and the percentage of NDMA removed also increased slightly; however, it did not improve the effectiveness of the UV-LED-based AOP. We conclude from this study that despite the advantages of the UV-LED over the conventional LP Hg UV lamp, the former performs ineffectively at attenuating major CECs in recycled water

Characterisation of tyrosinase for the treatment of aqueous phenols

Mushroom tyrosinase (polyphenol oxidase, EC 1.14.18.1) was investigated as an alternative to peroxidase, enzymes for the catalytic removal of phenolic compounds from wastewaters. The maximum catalytic activity was observed at pH 7; however, significant activity was observed at pHs ranging from 5 to 8. Tyrosinase was unstable under acidic conditions and at elevated temperatures. The activation energy for thermal inactivation of tyrosinase was determined to be 1.85 kJ mol-1 at pH 7. The transformation of phenols catalysed, by tyrosinase was investigated as a function of pH, initial phenol concentration, and additives. Phenol was transformed successfully with tyrosinase, over a wide range of pH (pH 5--8) and a wide range of initial concentrations (0.5 mM--10 mM). Some chlorinated phenols were also successfully transformed with tyrosinase. Polyethylene glycol and chitosan did not improve the transformation efficiency of phenol. However, chitosan was successfully used to remove coloured, products resulting from treatment Since coagulation with aluminium sulfate failed, the colour removal induced by chitosan addition appeared to be the result of simultaneous coagulation and adsorption mechanisms. Minimum doses of chitosan required to achieve 90% of colour removal were logarithmically related to the quantity of phenol treated. All solutions of phenol and chlorophenols treated with tyrosinase, had substantially lower toxicities, than their corresponding initial toxicities. Chitosan addition enhanced the reduction in toxicity very effectively. The toxicities of the phenol solutions treated with tyrosinase were markedly lower than previously reported toxicities of solutions treated with peroxidase enzymes

Health effects associated with wastewater treatment, reuse, and disposal

A review of the literature published in 2008 on topics relating to the health effects associated wastewater treatment, reuse, and disposal is presented. The following topics are covered: treatment (occupational health), discharge (chemical and microbial contamination, health effects in aquatic organisms, rural regions, and industrial wastewater), and reuse (irrigation and non-portable reuse, potable reuse, livestock health, and biosolids).</p

Health effects associated with wastewater treatment, reuse, and disposal

A review of the literature published in 2009 on topics relating to the health effects associated with wastewater treatment, reuse, and disposal is presented. The following topics are covered: wastewater management, microbial and chemical contaminants, ecotoxicity and ecotoxicology, contamination of recreational water, water reclamation and reuse, risk assessment and management, industrial wastewater, wastewater treatment plants, and other miscellaneous issues.</p

Agricultural wastes

This review summarizes the literature related to agricultural wastes published during 2009. The review is divided into the following sections: waste characterization, waste management and pollution minimization, waste treatment, and waste recycle and reuse.</p

Agricultural wastes

This review summarizes the literature related to agricultural wastes published during 2008. This review is divided into the following sections: waste characterization, waste management and pollution minimization, waste treatment, and waste recycle and reuse.</p

Water recovery from advanced water purification facility reverse osmosis concentrate by photobiological treatment followed by secondary reverse osmosis

Reverse osmosis (RO)-based desalination and advanced water purification facilities have inherent challenges associated with concentrate management and disposal. Although enhanced permeate recovery and concentrate minimization are desired, membrane scaling due to inorganic constituents, such as silica, calcium, phosphate, and iron, hinders the process. To solve this problem, a new diatom-based photobiological process has been developed to remove these scaling constituents by biological uptake and precipitation. In this study, RO concentrate samples were collected from a full-scale advanced water reclamation facility in California and were treated in 3.8 and 57 L photobioreactors inoculated with a brackish water diatom  Pseudostaurosira trainorii PEWL001 using light-emitting diode bulbs or natural sunlight as a light source. The photobiological treatment removed 95% of reactive silica and 64% of calcium and enabled additional water recovery using a secondary RO at a recovery rate up to 66%. This represents 95% overall recovery, including 85% recovery in the primary RO unit. In addition to the scaling constituents, the photobiological treatment removed 12 pharmaceuticals and personal care products, as well as N-nitrosodimethylamine, from RO concentrate samples primarily via photolysis. This novel approach has a strong potential for application to brackish water desalination and advanced water purification in arid and semiarid areas.Accepted versio