Evaluating the effectiveness of minimum chlorate technologies employed by manufacturers of skim milk powder from both microbiological quality and chemical residue perspectives

Dairy processors in the Republic of Ireland have adopted chlorine-free chemicals for cleaning and chlorine gas for water disinfection as a means of minimizing chlorate residue in dairy products. For these 'minimum chlorate technologies' to be satisfactory, they must be able to deliver product with acceptable levels of bacteria as well as minimum levels of chlorate and other chlorine based residues. To establish the effectiveness of these technologies, sampling was conducted across the skim milk powder (SMP) manufacturing chain in 3 separate milk processing sites. Across the 3 sites a total of 11 different batches of SMP were sampled in duplicate from the whole milk silo through the manufacturing process to the powder product; yielding a total of 137 samples. Samples were tested for chlorate, perchlorate and trichloromethane alongside a suite of microbiological plate count tests including total bacteria, thermophilic bacteria, thermoduric bacteria and both mesophilic and thermophilic spore-forming bacteria. Chlorate was detected at reportable levels (≥0.01 mg/kg) in 9 of 22 SMP samples analyzed; resulting in a mean chlorate concentration 0.0183 mg/kg. Bacteria were ubiquitous across all samples analyzed with spore-forming bacteria counts ranging from 1.30 to 2.33 log cfu/ g in SMP.

Chlorate Levels in Dairy Products Produced and Consumed in Ireland

In recent years, chlorate has become a residue of concern internationally, due to the risk that it poses to thyroid gland function. However, little is known about its occurrence in dairy products of Irish origin. To address this, a study was conducted in which samples of milk (n = 317), cream (n = 199), butter (n = 178), cheese (n = 144) and yoghurt (n = 440) were collected from grocery stores in the Republic of Ireland. Sampling was conducted across spring, summer, autumn and winter of 2021. Samples from multiple manufacturers of each respective dairy product were procured and analysed for chlorate using UPLC-MS/MS. Chlorate was detected in milk, cream, natural, blueberry, strawberry and raspberry yoghurts. Mean chlorate levels detected in these products were 0.0088, 0.0057, 0.055, 0.067, 0.077 and 0.095 mg kg^-1, respectively. Chlorate was undetected in butter and cheese (<0.01 mg kg^-1). All products sampled, except yoghurt, were found to be compliant with the EU limit for chlorate in milk (0.10 mg kg^-1). Some manufacturers produced product with greater incidence and levels of chlorate. Chlorate levels from samples tested at different times of the year did not differ significantly, with the exception of strawberry and raspberry yoghurts which had higher chlorate levels in the winter period.

Application of Prussian Blue in Electrochemical and Optical Sensing of Free Chlorine

In this paper, an electrochemical free chlorine (FCL) sensor was formed by modifying a fluorine-doped tin oxide-coated glass slide (glass|FTO) with a layer of Prussian blue (glass|FTO|PB). The glass|FTO|PB sensor exhibited a wide linear detection range from 1.7 to 99.2 μmol L^-1 of FCL with a sensitivity of ~0.8 µA cm^-2 μmol^-1 L and showed high selectivity for FCL. However, ClO3-, ClO4- and NO3- ions have induced only a negligible amperometric response that is highly beneficial for a real-life sample analysis as these ions are commonly found in chlorine-treated water. Moreover, in this work, optical absorption measurement-based investigations of partially reduced PB were carried out as a means to characterize PB catalytic activity towards FCL and to investigate the possibility of applying PB for the optical detection of FCL.

Sensor Data Fusion as an Alternative for Monitoring Chlorate in Electrochlorination Applications

As chlorate concentrations have been found to be harmful to human and animal health, governments are increasingly demanding strict control of the chlorate concentration in drinking water. Since there are no chlorate sensors available, the current solution is sampling and laboratory analysis. This is costly and time consuming. The aim of this work was to investigate Sensor Data Fusion (SDF) as an alternative approach, with a focus on chlorate formation in the electrochlorination process, and design an observer for the real-time estimation of chlorate. The pH, temperature and UV-a absorption were measured in real time. A reduced-order nonlinear model was derived, and it was found to be detectable. An Extended Kalman Filter (EKF), based on this model, was then used to estimate the chlorate formation. The EKF algorithm was verified experimentally and was found to be capable of accurately estimating chlorate concentrations in real time. Electrochlorination is an emerging and efficient method of disinfecting drinking water. Soft sensing of chlorate concentrations, as proposed in this paper, may help to better control and manage the process of electrochlorination.

Comparison of Peracetic Acid and Chlorine Effectiveness during Fresh-Cut Vegetable Processing at Industrial Scale

ABSTRACT

This study was conducted to compare the efficacy of two sanitizing agents, chlorine and peracetic acid (PAA), in reducing spoilage and pathogenic microorganisms and disinfection by-products in the washing stage of three types of minimally processed vegetables: iceberg lettuce, carrots, and baby leaves. These fresh-cut products are consumed uncooked; thus, proper sanitation is essential in preventing foodborne illness outbreaks. The comparison was done at industrial scale with equipment already used in the fresh-cut industry and with washers designed and manufactured for this purpose. Results showed that for washing water hygiene and final product microbial quality, the use of PAA or chlorine had similar efficacy. Different scenarios combining PAA, chlorine, and water were tested, simulating the current industrial processes for each of the tested vegetables. Overall, results confirmed that the use of a sanitizer, PAA or chlorine, in the washing water is effective for the prevention of cross-contamination during the washing process and hence for produce food safety. For final product microbiological quality and shelf life, the use of chlorine or PAA showed no significant differences in lettuce or baby leaves. Chlorinated disinfection by-products in processing water were not formed in significant amounts when washing water was treated with PAA in all scenarios and for all tested vegetables, whereas washing with chlorine (80 mg/L) generated important amounts of trihalomethanes, chlorates, and chlorites. Although chlorates and chlorites were always below the recommended levels or legal limits established for drinking water, trihalomethanes exceeded the legal limits. For perchlorates, values were below the quantification limit in all scenarios. Our results show that PAA is a reliable alternative to chlorine disinfection strategies in the fresh-cut industry.

HIGHLIGHTS

Demonstration-scale evaluation of ozone-biofiltration-granular activated carbon advanced water treatment for managed aquifer recharge

The Sustainable Water Initiative for Tomorrow (SWIFT) program is the effort of the Hampton Roads Sanitation District to implement indirect potable reuse to recharge the depleted Potomac Aquifer. This initiative is being demonstrated at the 1-MGD SWIFT Research Center with a treatment train including coagulation/flocculation/sedimentation (floc/sed), ozonation, biofiltration (BAF), granular activated carbon (GAC) adsorption, and UV disinfection, followed by managed aquifer recharge. Bulk total organic carbon (TOC) removal occurred via multiple treatment barriers including, floc/sed (26% removal), ozone/BAF (30% removal), and adsorption by GAC. BAF acclimation was observed during the first months of plant operation which coincided with the establishment of biological nitrification and dissolved metal removal. Bromate formation during ozonation was efficiently controlled below 10 µg/L using preformed monochloramine and preoxidation with free chlorine. N-nitrosodimethylamine (NDMA) was formed at an average concentration of 53 ng/L post-ozonation and was removed >70% by the BAFs after several months of operation. Contaminants of emerging concern were removed by multiple treatment barriers including oxidation, biological degradation, and adsorption. The breakthrough of these contaminants and bulk TOC will likely determine the replacement interval of GAC. The ozone/BAC/GAC treatment process was shown to meet all defined treatment goals for managed aquifer recharge. PRACTITIONER POINTS: Floc/sed, biofiltration, and GAC adsorption provide important barriers in carbon-based treatment trains for bulk TOC and trace organic contaminant removal. Biofilter acclimation was observed during the first three months of operation in each operating period as evidenced by the establishment of nitrification. Bromate was effectively controlled during ozonation of a high bromide water with monochloramine doses of 3-5 mg/L. NDMA was formed at an average concentration of 53 ng/L by ozonation and complete removal was achieved by BAFs after several months of biological acclimation. An average 25% removal of 1,4-dioxane was achieved via oxidation by hydroxyl radicals during ozonation.

Occurrence and fate of ozonation disinfection by-products in two Canadian drinking water systems

The occurrence and the fate of 18 ozonation by-products (OBPs) (17 different aldehydes and bromate) were studied over one year in two Canadian drinking water systems. This is the first and only study reporting the occurrence of all these non-halogenated aldehydes (NON-HALs) and haloacetaldehydes (HALs) simultaneously, based on the multi-point monitoring of water in full-scale conditions from source to distribution network. In general, the application of both post-ozonation and liquid chlorine contributed to the formation of OBPs (aldehydes and bromate). NON-HALs were present in higher concentrations than HALs. Formaldehyde, acetaldehyde, glyoxal and methylglyoxal were the most common forms of NON-HALs in the two water systems that were studied. Chloral hydrate (CH), the hydrated form of trichloroacetaldehyde, was the most dominant HAL observed. The nature of the organic matter and the water temperature proved to be important parameters for explaining the variability of aldehydes. Summer and autumn (warm seasons) were more favorable for the formation of chloral hydrate and bromate. The highest concentrations of NON-HALs were observed in spring.

Bioelectrochemical chlorate reduction by Dechloromonas agitata CKB

Chlorate has been described as an emerging pollutant that compromises water sources. In this study, bioelectrochemical reactors (BERs) using Dechloromonas agitata CKB, were evaluated as a sustainable alternative for chlorate removal. BERs were operated under flow-recirculation and batch modes with an applied cell-voltage of 0.44 V over a resistance of 1 kΩ. Results show chlorate removal up to 607.288 mg/L. After 115 days, scanning electron microscopy showed biofilm development over the electrodes, and electrochemical impedance spectroscopy confirmed the biocatalytic effect of CKB. The theoretical chlorate bioreduction potential (ε° = 0.792 V) was proven, and a kinetic study indicated that 6 electrons were involved in the reduction mechanism. Finally, a hypothetical bioelectrochemical mechanism for chlorate reduction in a BER was proposed. This research expands upon current knowledge of novel electrochemically active microorganisms and widens the scope of BER applications for chlorate removal.

Hydrogenation of chlorate ions by commercial carbon supported palladium catalysts—a comparative study

The chlorate elimination potential of three commercial activated carbon supported 10 wt% palladium catalysts (Cat-I, Cat-II and Cat-III) have been compared in heterogeneous catalytic hydrogenation. The physical–chemical properties of the catalysts were characterized by using high-resolution transmission electron microscopy, X-ray diffractometry, Fourier-transform infrared spectroscopy and ζ potential measurements. Chlorate reduction tests have been carried out by applying the same procedure and conditions in each case. The studied catalysts were active, but Cat-I and Cat-III showed higher activity, and eliminated 93% and 91% of chlorate, respectively. Reuse tests have also been carried out to compare the catalysts. Although Cat-I and Cat-III were shown almost equally high activity in the first cycle, the reuse tests showed that Cat-III could have a better applicability.

Disinfection for decentralized wastewater reuse in rural areas through wetlands and solar driven onsite chlorination

Increasing water scarcity is of growing concern in Europe, especially in Mediterranean countries along coastlines. Wastewater reuse reduces water stress, but often requires the absence of pathogen indicators and the application of chlorine to assure residual disinfection. However, the effluent qualities of typical Wastewater Treatment Plants (WWTP) show immense chlorine demands. This makes the supply, handling and dosing of typical WWTP effluent challenging, especially in rural regions. In the work presented here, a vertical flow constructed wetland (VFCW) was combined with a small-scale solar-driven Onsite Chlorine Generation system (OCG) to further improve effluent qualities for different WWTPs and to produce chlorine stock solution directly at the site. To test different operational conditions the VFCW received WWTP effluent from a) an Activated Sludge and b) a High-Rate Algae Pond system. The VFCW reduced TSS by 92%, COD by 80%, and NH₄ by over 99% and the chlorine demand by 85%. The log-unit reduction of the VFCW/OCG system reached ≥5.1 for total coliforms and ≥4.6 for E. Coli. During VFCW passage the already high electrical conductivity further increased to beyond permissible reuse limits due to high evapotranspiration (ET) rates of the planted vegetation Arundo donax. Unique aspects of this setup were that neither chemicals nor external electricity were required to run the system. The elevated chloride concentration of the treated WW (819 ± 132 mg/L) proved sufficient for the production of chlorine stock solution. However, the solar-driven OCG system tested here consumed considerably more electricity compared to other OCGs available on the market. Nevertheless, the system presented here may be considered an efficient disinfection alternative for decentralized WW reuse applications at remote sites with both limited access to grid electricity and strict requirements for pathogen indicators.

LC-ESI-MS/MS determination of oxyhalides (chlorate, perchlorate and bromate) in food and water samples, and chlorate on household water treatment devices along with perchlorate in plants

The results of the validation study of the LC-ESI-MS/MS method for the determination of chlorate (ClO₃^-), perchlorate (ClO₄^-) and bromate (BrO₃^-) in water and food samples are summarized. Towards this, 284 samples of drinking water were analysed, out of which the 69% contained chlorate above the limit of quantitation (LOQ) of 0.01 mg/L, with maximum amount of 1.1 mg/L. Only 6 samples were found to be positive with perchlorate at levels <0.01 mg/L. Bromate was detected in 5 drinking water samples at levels above the LOQ, at concentrations up to 0.026 mg/L. For the validation of the method in food, 108 blank samples were spiked with chlorate and perchlorate for the LC-MS/MS analysis at two levels. In total 247 food samples from the market of 19 different commodities including fruits, vegetables, cereals and wine, were analysed. The maximum concentration of chlorate was found at 0.83 mg/kg in a sample of cultivated mushrooms. The number of samples contaminated with perchlorate was also small, with all the determined concentrations below the LOQ of 0.05 mg/kg. Experiments for the chlorate reduction in drinking water, showed that reverse osmosis treatment is effective in particular with newly installed cartridges. Finally, according to the results of the pilot study when chlorinated water is used for the plant irrigation, accumulation of chlorate is observed, especially in the green parts of the plant. Perchlorate was also detected in leafy samples, although it was not present in the irrigation water.

A twist six-membered rhodamine-based fluorescent probe for hypochlorite detection in water and lysosomes of living cells

A novel six-membered rhodamine-based fluorescent probe (6G-ClO) was developed from 2-formyl rhodamine (6G-CHO) and used for hypochlorite detection in water and HUVEC cells. Different from planar penta cycle of rhodamine spirolactam, there was a twist six-membered spirocyclic hydrazone in 6G-ClO optimized by Gaussian software at DFT/B3LYP/6-31G(d) level. The high selectivity, high sensitivity and fast response of 6G-ClO towards ClO^- would be attributed to the twist six-membered spirocycle. Test-strip prepared with 6G-ClO was successfully used to semi-quantitatively indicate the concentration of ClO^- in water. 6G-ClO can also quantitatively detect the concentration of ClO^- in tap water and swimming pool water. The detection limit of 6G-ClO was as low as 12 nM. The co-localization staining of HUVEC cells further verified that 6G-ClO could specifically accumulate in lysosomes and capture exogenous/endogenous ClO^- in living lysosomes. 6G-ClO would be a practical probe for real-time monitoring of ClO^- in the biological and real water samples.

Worldwide occurrence and origin of perchlorate ion in waters: A review

Perchlorate (ClO₄^-) is a persistent water soluble oxyanion of growing environmental interest. Perchlorate contamination can be a health concern due to its ability to disrupt the use of iodine by the thyroid gland and the production of metabolic hormones. Its widespread presence in surface water and groundwater makes the aquatic environment a potential source of perchlorate exposure. However, the amount of published data on perchlorate origins and water contamination worldwide remains spatially limited. Here, we present an overview of research on perchlorate origins and occurrences in water, and the methodology to distinguish the different perchlorate sources based on isotope analysis. All published ranges of isotopic content in perchlorate from different sources are presented, including naturally occurring and man-made perchlorate source types, as well as the effects of isotope fractionation that accompanies biodegradation processes. An example of a case study in France is presented to emphasize the need for further research on this topic.

Chloroxyanion Residue on Seeds and Sprouts after Chlorine Dioxide Sanitation of Alfalfa Seed

The effects of a 6-h chlorine dioxide sanitation of alfalfa seed (0, 50, 100, and 200 mg/kg seed) on total coliform bacteria, seed germination, and the presence of chlorate and perchlorate residues in seed rinse, seed soak, and alfalfa sprouts was determined. Chlorate residues in 20,000 mg/L calcium hypochlorite, commonly used to disinfect seed, were quantified. Chlorine dioxide treatment reduced (P < 0.05) total coliforms on seeds with no effect (P > 0.05) on germination. Dose-dependent sodium chlorate residues were present in seed rinse (4.1 to 31.2 μg/g seed) and soak (0.7 to 8.3 μg/g seed) waters, whereas chlorate residues were absent (LOQ 5 ng/g) in sprouts, except for 2 of 5 replicates from the high chlorine dioxide treatment. Copious chlorate residues were present (168 to 1260 mg/L) in freshly prepared 20,000 mg/L calcium hypochlorite solution, and storage at room temperature increased chlorate residues significantly (P < 0.01).

We are what we eat: Regulatory gaps in the United States that put our health at risk

The American diet has changed dramatically since 1958, when Congress gave the United States Food and Drug Administration (FDA) the authority to ensure the safety of chemicals in food. Since then, thousands of chemicals have entered the food system. Yet their long-term, chronic effects have been woefully understudied, their health risks inadequately assessed. The FDA has been sluggish in considering scientific knowledge about the impact of exposures-particularly at low levels and during susceptible developmental stages. The agency's failure to adequately account for the risks of perchlorate-a well-characterized endocrine-disrupting chemical-to vulnerable populations is representative of systemic problems plaguing the regulation of chemicals in food. Today, we are faced with a regulatory system that, weakened by decades of limited resources, has fallen short of fully enforcing its mandates. The FDA's inability to effectively manage the safety of hundreds of chemicals is putting our children's health at risk.

Perchlorate and Diet: Human Exposures, Risks, and Mitigation Strategies

Perchlorate is an endocrine-disrupting chemical that interferes with the normal functioning of the thyroid gland. Maternal thyroid dysfunction during gestation may alter fetal brain development. Perchlorate contamination is widespread: it is present in the body of all Americans tested and the majority of foods tested. The main sources of food contamination appear to be hypochlorite bleach, a disinfectant and sanitizer, that when poorly managed quickly degrades to perchlorate and perchlorate-laden plastic food packaging for dry food or localized contamination from manufacturing or processing of the chemical. Eliminating perchlorate from food packaging and improving bleach management, such as reducing concentration and storage time and temperature, would result in reduced perchlorate contamination of food and water.

Distribution, Identification, and Quantification of Residues after Treatment of Ready-To-Eat Salami with 36Cl-Labeled or Nonlabeled Chlorine Dioxide Gas

When ready-to-eat salami was treated in a closed system with ³⁶Cl-labeled ClO₂ (5.5 mg/100 g of salami), essentially all radioactivity was deposited onto the salami. Administered ³⁶ClO₂ was converted to ³⁶Cl-chloride ion (>97%), trace levels of chlorate (<2%), and detectable levels of chlorite. In residue studies conducted with nonlabeled ClO₂, sodium perchlorate residues (LOQ, 4 ng/g) were not formed when reactions were protected from light. Sodium chlorate residues were present in control (39.2 ± 4.8 ng/g) and chlorine dioxide treated (128 ± 31.2 ng/g) salami. If sanitation occurred under conditions of illumination, detectable levels (3.7 ± 1.5 ng/g) of perchlorate were formed along with greater quantities of sodium chlorate (183.6 ± 75.4 ng/g). Collectively, these data suggest that ClO₂ is chemically reduced by salami and that slow-release formulations might be appropriate for applications involving the sanitation of ready-to-eat meat products.

Formation of disinfection by-products in the ultraviolet/chlorine advanced oxidation process

Disinfection by-product (DBP) formation may be a concern when applying ultraviolet light and free chlorine (UV/chlorine) as an advanced oxidation process (AOP) for drinking water treatment, due to typically large chlorine doses (e.g. 5-10 mg L(-1) as free chlorine). A potential mitigating factor is the low chlorine contact times for this AOP treatment (e.g. seconds). Full-scale and pilot-scale test results showed minimal trihalomethane (THM) and haloacetic acid (HAA) formation during UV/chlorine treatment, while dichloroacetonitrile (DCAN) and bromochloroacetonitrile (BCAN) were produced rapidly. Adsorbable organic halide (AOX) formation was significant when applying the UV/chlorine process in water that had not been previously chlorinated, while little additional formation was observed in prechlorinated water. Chlorine photolysis led to chlorate and bromate formation, equivalent to approximately 2-17% and 0.01-0.05% of the photolyzed chlorine, respectively. No perchlorate or chlorite formation was observed. During simulated secondary disinfection of AOP-treated water, DBP formation potential for THMs, HAAs, HANs, and AOX was observed to increase approximately to the same extent as was observed for pretreatment using the more common AOP of UV combined with hydrogen peroxide (UV/H2O2).

Electrochemical disinfection using boron-doped diamond electrode--the synergetic effects of in situ ozone and free chlorine generation

This work investigated the capability of using a boron-doped diamond (BDD) electrode for bacterial disinfection in different water matrices containing varying amounts of chloride. The feed water containing Pseudomonas aeruginosa was electrochemically treated while applying different electrode conditions. Depending on the applied current density and the exposure time, inactivation between 4- and 8-log of the targeted microorganisms could be achieved. The disinfection efficiency was driven by the generation of free chlorine as a function of chloride concentration in the water. A synergetic effect of generating both free chlorine and ozone in situ during the disinfection process resulted in an effective bactericidal impact. The formation of the undesired by-products chlorate and perchlorate depended on the water matrix, the applied current density and the desired target disinfection level. In case of synthetic water with a low chloride concentration (20 mg L(-1)) and an applied current density of 167 mA cm(-2), a 6-log inactivation of Pseudomonas aeruginosa could be achieved after 5 min of exposure. The overall energy consumption ranged between 0.3 and 0.6 kW h m(-3) depending on the applied current density and water chemistry. Electrochemical water disinfection represents a suitable and efficient process for producing pathogen-free water without the use of any chemicals.

Perchlorate production by photodecomposition of aqueous chlorine solutions

Aqueous chlorine solutions (defined as chlorine solutions (Cl(2,T)) containing solely or a combination of molecular chlorine (Cl(2)), hypochlorous acid (HOCl), and hypochlorite (OCl(-))) are known to produce toxic inorganic disinfection byproduct (e.g., chlorate and chlorite) through photoactivated transformations. Recent reports of perchlorate (ClO(4)(-)) production-a well-known thyroid hormone disruptor- from stored bleach solutions indicates the presence of unexplored transformation pathway(s). The evaluation of this potential ClO(4)(-) source is important given the widespread use of aqueous chlorine as a disinfectant. In this study, we perform detailed rate analysis of ClO(4)(-) generation from aqueous chlorine under varying environmental conditions including ultraviolet (UV) light sources, intensity, solution pH, and Cl(2,T) concentrations. Our results show that ClO(4)(-) is produced upon UV exposure of aqueous chlorine solutions with yields ranging from 0.09 × 10(-3) to 9.2 × 10(-3)% for all experimental conditions. The amount of ClO(4)(-) produced depends on the starting concentrations of Cl(2,T) and ClO(3)(-), UV source wavelength, and solution pH, but it is independent of light intensity. We hypothesize a mechanistic pathway derived from known reactions of Cl(2,T) photodecomposition that involves the reaction of Cl radicals with ClO(3)(-) to produce ClO(4)(-) with calculated rate coefficient (k(ClO4-)) of (4-40) × 10(5) M(-1) s(-1) and (3-250) × 10(5) M(-1) s(-1) for UV-B/C and UV-A, respectively. The measured ClO(4)(-) concentrations for both UV-B and UV-C experiments agreed well with our model (R(2) = 0.88-0.99), except under UV-A light exposure (R(2) = 0.52-0.93), suggesting the possible involvement of additional pathways at higher wavelengths. Based on our results, phototransformation of aqueous chlorine solutions at concentrations relevant to drinking water treatment would result in ClO(4)(-) concentrations (~0.1 μg L(-1)) much below the proposed drinking water limits. The importance of the hypothesized mechanism is discussed in relation to natural ClO(4)(-) formation by atmospheric transformations.