Reduction of Carbonaceous and Nitrogenous Disinfection Byproduct Precursors from Coagulated/Filtered Algae-laden Water: Comparison of Vacuum Ultraviolet and Ultraviolet Processes with and without Persulfate Activation

The increased mutagenicity of disinfection by‐products (DBPs) containing bromide (Br−) and nitrogen requires a renewed evaluation of best available treatment technologies for DBP control. The aim of this article is to document the removal of organic nitrogen during granular activated carbon (GAC) treatment and to illustrate how GAC treatment alters DBP speciation. Rapid small‐scale column tests (RSSCTs) with GAC were conducted on pretreated surface water sources to evaluate the simultaneous removal of carbonaceous and nitrogenous DBP precursors: dissolved organic nitrogen (DON), dissolved organic carbon (DOC), organics absorbed by ultraviolet light at 254 nm (UV254), and Br−. Simulated distribution system tests were conducted with RSSCT effluent samples throughout natural organic matter breakthrough, and free chlorine was used to evaluate the formation of halogenated carbonaceous and nitrogenous DBPs. GAC preferentially removed UV254‐absorbing material over DOC, which was removed more effectively than DON. Br− was not removed. Consequently, effluent ratios of Br− to DOC and Br− to DON changed during GAC treatment, and the ratio of brominated DBPs to chlorinated DBPs shifted during the GAC breakthrough cycle; brominated DBPs dominated earlier in the breakthrough of DOC. Neither DON nor nitrogenous DBP precursors were removed efficiently during GAC treatment.

Hurricane resulted in releasing more nitrogenous than carbonaceous disinfection byproduct precursors in coastal watersheds

Prechlorination of algae-laden water: The effects of transportation time on cell integrity, algal organic matter release, and chlorinated disinfection byproduct formation

Carbonaceous and nitrogenous disinfection byproduct precursor variation during the reversed anaerobic–anoxic–oxic process of a sewage treatment plant

Nitrogen-containing organic compounds and nitrogenous disinfection by-products (N-DBPs) in drinking water have attracted attention in the field of water treatment. Metabolites released during algae growth contain a variety of organic nitrogen species, which are called N-DBP precursors. The aim of this paper is to elucidate how N-DBP precursors are released under UV radiation, as well as investigate the variations of their chemical properties. The results show that through UV radiation, the physiological metabolism of algal cells was disordered and the properties of their metabolites were changed. The dissolved organic nitrogen (DON) compound concentration increased rapidly from 5.38 at the beginning to 11.11 mg/L after 30 min of radiation, and then increased steadily from 11.11 to 23.71 mg/L during a further 210 min of radiation. Derivation results of the curves for algae and DON concentration variations shows that when 1 × 1010 algal cells were destroyed, 8.31 mg DON was released into the solution during the first 30 min of radiation. Low dose UV radiation brought a slight decline of the specific N-DBP formation potential due to changes in the extracellular organic matter (EOM) structure without destroying the algal cells, which was conducive to controlling the formation potential of N-DBPs. Long-time UV radiation can bring a significant increase in N-DBP formation potential. After 4 hours of ultraviolet radiation, the total formation potential of N-DBPs in the solution increased from about 84.9 μg/L to about 213.5 μg/L, 2.5 times higher than the initial solution. The N-DBP formation potential increases obviously during the first 10–30 min UV radiation, and then decreases slightly in the subsequent 30–240 min radiation.

Removal of precursors of typical nitrogenous disinfection byproducts in ozonation integrated with biological activated carbon (O3/BAC)

Effect of prescribed fires on the export of dissolved organic matter, precursors of disinfection by-products, and water treatability

Exploring the impacts of service life of biological activated carbon on dissolved organic nitrogen removal

Drinking water quality can be impacted by the presence of algogenic organic matter (AOM), rich in dissolved organic nitrogen (DON) that can act as precursors of nitrogenous disinfection by-products (N-DBPs). Better characterisation of algogenic DON is therefore important in order to optimise treatment processes so that N-DBP concentrations in treated water are minimised. This paper characterises the DON exuded by the green algae Chlorella vulgaris and the cyanobacteria Microcystis aeruginosa and Anabaena circinalis using ultrafiltration, measurements of total organic carbon and total nitrogen (TOC/TN), dissolved inorganic nitrogen (DIN), and size exclusion liquid chromatography detection with organic carbon and nitrogen detection (SEC-LC-OCD-OND). Potential N-DBP formation of three haloacetonitriles (HANs), two halonitromethanes (HNMs) and two haloacetamides (HAAms) was evaluated by chlorination of fractional AOM with a mass ratio of free Cl2: TOC of 8:2, and subsequently measuring target N-DBPs using GC-MS. Results showed that AOM primarily contained org-N contents at >50 kDa and around 1 kDa. Among the chlorinated AOM, only HANs were detected in N-DBP formation experiments. The algal species and fractions containing higher org-N content produced greater HAN. The fractional high molecular weight (HMW) AOM (1–50 kDa) of Anabaena circinalis had the highest yield of dichloroacetonitrile (DCAN) at 2.4 µgL−1 or 1.2 µgmg−1C−1. Overall, there was more N-DBP formation from HMW AOM fractions than low molecular weight (LMW) AOM fractions.

Dissolved inorganic nitrogen as an overlooked precursor of nitrogenous disinfection byproducts - A critical review

Transforming dissolved organic matter (DOM) is a crucial approach to alleviating the formation of disinfection byproducts (DBPs) in water treatment. Although catalytic ozonation effectively transforms DOM, increases in DBP formation potential are often observed due to the accumulation of aldehydes, ketones, and nitro compound intermediates during DOM transformation. In this study, we propose a novel strategy for the sequential oxidation of DOM, effectively reducing the levels of accumulation of these intermediates. This is achieved through the development of a catalyst with a tailored surface and nanoconfined active sites for catalytic ozonation. The catalyst features a unique confinement structure, wherein Mn-N4 moieties are uniformly anchored on the catalyst surface and within nanopores (5-20 Å). This design enables the degradation of the large molecular weight fraction of DOM on the catalyst surface, while the transformed smaller molecular weight fraction enters the nanopores and undergoes rapid degradation due to the confinement effect. The generation of *Oad as the dominant reactive species is essential for effectively reducing these ozone refractory intermediates. This resulted in over 70% removal of carbonaceous and nitrogenous DBP precursors as well as brominated DBP precursors. This study highlights the importance of the nanoscale sequential reactor design and provides new insights into eliminating DBP precursors by the catalytic ozonation process.

Biological aerated filters (BAFs) are widely used for the treatment of micropolluted surface water. However, the biological process produces dissolved organic nitrogen (DON), which, as precursors of nitrogenous disinfection by-products, pose potential threats to drinking water safety. Therefore, to control DON in BAF effluent, it is necessary to study the influence of BAF operation parameters on DON production. In this study, the influence of filtration velocity in a BAF on DON production was investigated. Under different filtration velocity (0.5, 2, and 4m/h) conditions, profiles of DON concentrations along the media layer were measured. The profile at a filtration velocity of 0.5m/h showed a decreasing trend, and the ones under filtration velocities of 2 and 4m/h fluctuated in a small range (from 0.1 to 0.4mg/L). Moreover, the relatively high filtration velocities of 2 and 4m/h resulted in a lower level of DON concentration. Additionally, 3D excitation-emission matrix fluorescence spectroscopy was used to characterize DON. It is found that the patterns of DON at a relatively high filtration velocity condition (4m/h) were obviously different from the ones under low filtration velocity conditions (0.5 and 2m/h).

Impact of backwash on biofiltration-related nitrogenous disinfection by-product formation

More and more attention is paid to dissolved organic nitrogen (DON) and some specific categories of amino acids are considered to be the direct precursors of nitrogenous disinfection byproducts (N-DBPs). Histidine was chosen to study the efficiency and mechanism of amino acid in UV/Cu-TiO2system. Moreover, the influences of pH, organics, and inorganic ion on the photocatalytic efficiency were also investigated. The results show that the degradation rate of DON in the UV/Cu-TiO2system was about 50% after 60 min, and it was much lower than that of histidine (72%), which indicated that a part of degraded histidine was oxidized to other N-containing organics. The optimal pH value was 7.0 for the photodegradation of histidine, and the presence of organic compound and inorganic ion would decrease the degradation performance to some extent. After 6 h irradiation, histidine was totally degraded intoNH4+, and in the following 2 h,NH4+was oxidized toNO3-firstly and thenNO3-was reduced to N2and overflowed from water, which should be attributed to the doping of Cu in the TiO2and provided a way to totally degrade the DON from the water.

Formation of disinfection byproducts from chlorinated soluble microbial products: Effect of carbon sources in wastewater denitrification processes