Using total adenosine triphosphate (tATP) measurements for cyanobacterial bloom monitoring and response assessment during algaecide treatments.

Total adenosine triphosphate (tATP) was investigated for its potential as a rapid indicator of cyanobacterial growth and algaecide effectiveness. tATP and other common bloom monitoring parameters were measured over the growth cycles of cyanobacteria and green algae in laboratory cultures and examined at a drinking water source during an active bloom. Strong correlations (R>0.

Kinetics of chlorine and chloramine reactions in reverse osmosis permeate and their impact on radical formation during UV/chlorine advanced oxidation for potable reuse.

Knowledge of the speciation of chlorine and chloramines in reverse osmosis (RO) permeate is needed to estimate the performance (i.e., pollutant log reduction) of subsequent UV/chlorine advanced oxidation processes (AOPs).

Predicting chlorine demand by peracetic acid in drinking water treatment.

Peracetic acid (PAA) may be used in drinking water treatment for pre-oxidation and mussel control at the intake. PAA may exert a downstream chlorine demand, but full details of this reaction have not been reported. There are three possible mechanisms of this demand: (1) PAA may react directly with chlorine; (2) PAA exists in equilibrium with hydrogen peroxide, which is known to react with chlorine; and (3) as HO reacts with chlorine, PAA will hydrolyze to form more HO to re-establish PAA/HO equilibrium, thereby serving as an indirect reservoir of chlorine demand.

On the increasing competitiveness of UV/Cl to UV/HO advanced oxidation as the organic carbon concentration increases.

UV/Cl and UV/HO are advanced oxidation processes (AOPs) used for drinking water treatment and water reuse. This work explored the hypothesis that UV/Cl becomes more competitive to UV/HO at neutral-to-high pH as the concentration of total organic carbon (TOC) increases. Lab experiments and kinetic modelling were used to compare initial pseudo first-order contaminant decay rate coefficients between the AOPs at various pH and TOC conditions.

Is In-Service Granular Activated Carbon Biologically Active? An Evaluation of Alternative Experimental Methods to Distinguish Adsorption and Biodegradation in GAC.

In-service granular activated carbon (GAC) may transform into biological activated carbon (BAC) and remove contaminants through both adsorption and biodegradation, but it is difficult to determine its biodegradative capacity. One approach to understand the GAC biodegradative capacity is to compare the performance between unsterilized and sterilized GAC, but the sterilization methods may not ensure effective microbial inhibition and may affect adsorption. This study identified the C-glucose respiration rate as the best metric to evaluate the effectiveness of three sterilization methods: sodium azide addition, autoclaving, and γ irradiation.

Evaluating perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) removal across granular activated carbon (GAC) filter-adsorbers in drinking water treatment plants.

Granular activated carbon (GAC) was harvested from six filter-adsorbers that are used for taste and odour control in three drinking water treatment plants in Ontario, Canada, and evaluated for the removal of perfluorooctanic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) using minicolumn tests under different operational conditions. Parallel column tests were conducted using unsterilized GAC and sterilized GAC to distinguish adsorption from potential biodegradation of PFOA and PFOS across the GAC. It was observed that the GAC could achieve approximately 20% to 55% of PFOA and PFOS removal even after a long period of GAC operation (e.

Evaluating the relative adsorption and biodegradation of 2-methylisoborneol and geosmin across granular activated carbon filter-adsorbers.

This study investigated the relative contributions of adsorption vs. biodegradation towards 2-methylisoborneol (MIB) and geosmin removal in the granular activated carbon (GAC) harvested from six filter-adsorbers in three drinking water treatment plants in the Great Lakes region. Column tests using azide-treated (sterilized) and untreated GAC in parallel were used to isolate the two effects.

Understanding adsorption and biodegradation in granular activated carbon for drinking water treatment: A critical review.

Drinking water treatment plants use granular activated carbon (GAC) to adsorb and remove trace organics, but the GAC has a limited lifetime in terms of adsorptive capacity and needs to be replaced before it is exhausted. Biological degradation of target contaminants can also occur in GAC filters, which might allow the GAC to remain in service longer than expected. However, GAC biofiltration remains poorly understood and unpredictable.

Evaluation of ultraviolet/peracetic acid to degrade M. aeruginosa and microcystins -LR and -RR.

The reactivity of peracetic acid (PAA) alone, and PAA exposed to ultraviolet radiation (UV), was investigated on Microcystis aeruginosa cells, and on microcystin-LR and -RR. Reaction rates between PAA and MC-LR (k = 3.46 M s) and MC-RR (k = 2.

Modeling the efficiency of UV at 254 nm for disinfecting the different layers within N95 respirators.

The study presented a Monte Carlo simulation of light transport in eight commonly used filtered facepiece respirators (FFRs) to assess the efficacy of UV at 254 nm for the inactivation of SARS-CoV-2. The results showed different fluence rates across the thickness of the eight different FFRs, implying that some FFR models may be more treatable than others, with the following order being (from most to least treatable): models 1512, 9105s, 1805, 9210, 1870+, 8210, 8110s and 1860, for single side illumination. The model predictions did not coincide well with some previously reported experimental data on virus inactivation when applied to FFR surfaces.

Machine learning for anomaly detection in cyanobacterial fluorescence signals.

Many drinking water utilities drawing from waters susceptible to harmful algal blooms (HABs) are implementing monitoring tools that can alert them to the onset of blooms. Some have invested in fluorescence-based online monitoring probes to measure phycocyanin, a pigment found in cyanobacteria, but it is not clear how to best use the data generated. Previous studies have focused on correlating phycocyanin fluorescence and cyanobacteria cell counts.

Wavelength-dependent time-dose reciprocity and stress mechanism for UV-LED disinfection of Escherichia coli.

Ultraviolet (UV) disinfection efficiency by low-pressure (LP) mercury lamp depends on the UV fluence (dose): the product of incident irradiance (fluence rate) and exposure time, with correction factors. Time-dose reciprocity may not always apply, as higher UV-LP inactivation of E. coli was obtained at a higher irradiance over shorter exposure time, for the same UV fluence.

Light propagation within N95 filtered face respirators: A simulation study for UVC decontamination.

This study presents numerical simulations of UVC light propagation through seven different filtered face respirators (FFR) to determine their suitability for Ultraviolet germicidal inactivation (UVGI). UV propagation was modeled using the FullMonte program for two external light illuminations. The optical properties of the dominant three layers were determined using the inverse adding doubling method.

External Standard Calibration Method To Measure the Hydroxyl Radical Scavenging Capacity of Water Samples.

The hydroxyl radical (OH) scavenging capacity is a useful parameter for the design and operation of an advanced oxidation process (AOP) in water treatment. The scavenging capacity may change with time, and it would be useful to continuously measure this change to be able to optimize AOP doses. In this study, we first reviewed current methods for scavenging capacity measurement to identify strengths and weaknesses of each method.

Chlorine is preferred over bisulfite for HO quenching following UV-AOP drinking water treatment.

Drinking water treatment using UV/HO advanced oxidation typically results in residual HO that requires quenching to minimize its interference with downstream processes. Chemical quenching using chlorine or bisulfite are options, but there is some uncertainty in the literature about the kinetics of the bisulfite reaction, with some reports quoting the reaction as fast, and others as slow. Part of the contradictory information may be due to interference in HO analysis by bisulfite.

Full-scale comparison of UV/HO and UV/Cl advanced oxidation: The degradation of micropollutant surrogates and the formation of disinfection byproducts.

The photolysis of chlorine by UV light leads to the formation of the hydroxyl radicals (OH) as well as reactive chlorine species (RCS) that can be effective as advanced oxidation processes (AOPs) for water treatment. Much of the research to date has been done at laboratory- or bench-scale. This study reports results from a model that demonstrates that the relative effectiveness of the UV/Cl AOP compared to the more traditional UV/HO AOP is a function of optical path length.

Cyanotoxins and Cyanobacteria Cell Accumulations in Drinking Water Treatment Plants with a Low Risk of Bloom Formation at the Source.

Toxic cyanobacteria have been shown to accumulate in drinking water treatment plants that are susceptible to algal blooms. However, the risk for plants that do not experience algal blooms, but that receive a low influx of cells, is not well known. This study determined the extent of cell accumulation and presence of cyanotoxins across the treatment trains of four plants in the Great Lakes region.

Evaluation of phosphorus removal from a lake by two drinking water treatment plants.

The impact of drinking water treatment plants on phosphorous in a lake has never been previously reported. In this mass balance study, phosphorus removal by a conventional plant and a membrane plant on Lake Simcoe was monitored. Approximately 16 kg of phosphorus per year were removed from the lake by the membrane plant, representing 72% of the influent phosphorous load to the plant.

Comments on a Method to Measure Sucralose Using UV Photodegradation Followed by UV Spectrophotometry.

A simple and quick method to measure sucralose in aqueous solution at concentrations in the order of 0.1-1.2 g·L-1 proposed by Idris et al.

A comparative study of the hydroxyl radical scavenging capacity of activated sludge and membrane bioreactor wastewater effluents.

This study evaluated the hydroxyl radical scavenging characteristics of wastewater from five membrane bioreactor (MBR) and five activated sludge (AS) systems. The average values of the characteristics of both wastewater types was found to be significantly different at a 90% confidence interval in terms UV absorbance at 254 nm, alkalinity, and biopolymer concentration. Effluent organic matter (EfOM), with an average kOH,EfOM of (2.

Fate of geosmin and 2-methylisoborneol in full-scale water treatment plants.

The increasing frequency and intensity of taste and odour (T&O) producing cyanobacteria in water sources is a growing global issue. Geosmin and 2-methylisoborneol (MIB) are the main cyanobacterial T&O compounds and can cause complaints from consumers at levels as low as 10 ng/L. However, literature concerning the performance of full-scale treatment processes for geosmin and MIB removal is rare.

Factors affecting lead release in sodium silicate-treated partial lead service line replacements.

Water quality parameters affecting sodium silicate performance in partial lead service line replacements were examined using a fractional factorial experimental design and static pipe systems. An external copper wire was used to create a galvanic connection between a former lead service line and a new copper pipe. The pipe systems were filled with lab prepared water made to mimic real water quality.