Bulk Water Quality Research Articles

The effects of water content on mineralogical and drainage quality dynamics in weathering mine waste rock

Water content plays a critical yet ambivalent role in the physical and geochemical stability of mine tailings and waste rock, but its effects on individual chemical weathering reactions (dissolution and precipitation) and bulk water quality remain poorly understood. We experimented with synthetic waste rock to quantitatively reconcile modal and textural mineralogical parameters (mineral size, association, and liberation) with leachate quality at different water saturation levels (5–100%). Leachate pH consistently decreased from a 13-week average of 6.14 at 100% saturation to 5.37 at 5% saturation. Simultaneously, mineralogical analyses revealed a reduction in the size of carbonate phases over the course of weathering, decreasing from 200 µm to 145 µm as water saturation increased from 5% to 100%, which could be a contributing factor to more alkaline pH in samples with higher water saturation. Total concentrations of iron (Fe) and copper (Cu) in solution increased with lower moisture, with Cu concentrations increasing 24-fold in samples at 5% saturation compared to full saturation. In contrast, arsenic (As) concentration increased with higher moisture levels, which we attribute to reduced galvanic protection of As-bearing pyrite from oxidation. Multivariate statistical evaluation allowed us to uncover correlations between water chemistry and mineralogical data (i.e., sulfide associations or phase perimeters) and to explain chemical differences between samples, particularly those at 100% and 5% water saturation. Our findings underscore the importance of conducting quantitative mineralogical investigations on mine waste materials and considering their stored water content in the formulation of mine waste management strategies.

Effect of flow fluctuation on water pollution in drinking water distribution systems

The detachment of biofilm caused by changes in hydraulic conditions is an essential reason for the pollution of water in the drinking water distribution system (DWDS). In this research, the effect of flow fluctuation on bulk water quality was studied. The turbidity, iron concentration, manganese concentration, the total number of bacteria, biodegradable dissolved organic carbon (BDOC), bacterial community structure, and pathogenic genes in bacteria of bulk water were analyzed. The results indicate that the detachment of biofilm caused by fluctuant flow and reverse flow (especially instant reverse flow) can lead to the pollution of water. Throughout the entire experimental period, the turbidity under fluctuant flow velocity is 4.92%∼49.44% higher than that under other flow velocities. BDOC concentration is 5.68%∼53.99% higher than that under low and high flow velocities. The flow fluctuation increases bacterial regrowth potential (BRP) and reduces the biological stability of the bulk water. Low flow velocity is more conducive to the expression of pathogenic functional genes. In the short term, the water quality under low flow velocity is the best. Nevertheless, in a long-term operation (about seven days later), the water quality under high flow velocity is better than that under other flow velocities. This research brings new knowledge about the fluctuant hydraulic conditions on the bulk water quality within the DWDS and provides data support for stable drinking water distribution.

Application of Ice Pigging in a Drinking Water Distribution System: Impacts on Pipes and Bulk Water Quality

Ice pigging is an emerging technique for pipe cleaning in drinking water distribution systems. However, substantial confusion and controversy exist on the potential impacts of ice pigging on bulk water quality. This study monitored the microstructural features and composition of sediments and microbial community structures in bulk water in eight multimaterial Chinese networks. Chloride concentration analysis demonstrated that separate cleaning of pipes with different materials in complex networks could mitigate the risk of losing ice pigs and degrading water quality. The microstructural and trace element characterization results showed that ice pigs would scarcely disturb the inner surfaces of long-used pipes. The bacterial richness and diversity of bulk water decreased significantly after ice pigging. Furthermore, correlations were established between pipe service age, temperature, and chloride and total iron concentrations, and the 15 most abundant taxa in bulk water, which could be used to guide practical ice pigging operations.

Unraveling the evolution of dissolved organic matter in full-scale A/A/O wastewater treatment process using size exclusion chromatography with PARAFAC and nonnegative matrix factorization analysis

Changes in spectral features and molecular weight (MW) of dissolved organic matter (DOM) along the A/A/O processes in eight full-scale wastewater treatment plants (WWTPs) were characterized using size exclusion chromatography with a diode array detector, a fluorescence detector and an organic carbon detector in tandem (SEC-DAD-FLD-OCD) as well as bulk water quality parameters. The parallel factor (PARAFAC) and the nonnegative matrix factorization (NMF) analyses have been effectively applied to the postprocessing of SEC-FLD fingerprints and SEC-OCD chromatograms, respectively. Individual SEC-FLD-PARAFAC or SEC-OCD-NMF components may span a broad range of MW, indicating that these SEC fractions within the same component were cognate and varied coherently across the dataset samples. The SEC-FLD-PARAFAC modeling and SEC-OCD-NMF analysis have clearly and concisely presented that the dramatic decreases of dissolved organic carbon, UV absorbance at 254 nm and protein-like fluorescence at Ex280/Em350 nm in the anaerobic process were primarily associated with the degradation of the large MW proteinaceous and polysaccharide-like biopolymers. It has also revealed that fluorescence of humic acid-like fractions increased significantly during the anaerobic process, but fluorescence of fulvic acid-like and humic substances’ building blocks decreased slightly. Laboratory experiments further confirmed the presence of the humification process in anaerobic processes, and the formation of humic acid-like fluorophores may be associated with carbohydrate metabolism. The combination of SEC-FLD-PARAFAC and SEC-OCD-NMF helped to establish the links between changes in bulk water quality parameters and the evolution of SEC MW fractions, which provides a more in-depth insight into wastewater DOM treatability and enables the optimization of wastewater treatment processes.

Efficient synergistic disinfection by ozone, ultraviolet irradiation and chlorine in secondary effluents

Disinfection of secondary effluents is vital to provide a sustainable aquatic environment, minimize microbial risks and guarantee public and environmental safety. This study investigated the effectiveness of six treatment trains including single and combined disinfection processes (i.e., ozone alone, ultraviolet (UV) irradiation alone, chlorine alone, sequential ozone-UV, sequential ozone-chlorine and sequential ozone-UV-chlorine) on bacterial inactivation, as well as bulk water quality parameters such as color, turbidity, absorbance at 254 nm (UV254), dissolved organic carbon (DOC) and fluorescence based on samples collected from an actual water reclamation plant (WRP). For the single disinfection processes, when the ozone, UV and chlorine doses reached 5 mg/L, 15 mJ/cm2 and 4 mg/L, respectively, the log removal of Escherichia coli (E. coli) reached 5 log. A trailing phenomenon was observed with further increases in the disinfectant dosage. Under the combined treatment scenarios, ozone pretreatment resulted in substantial removal of color, turbidity, UV254, fluorescence excitation-emission matrix (FEEM) and chlorine consuming organics, thus enhancing the efficiency of subsequent UV irradiation or chlorine treatments. In the sequential ozone-UV-chlorine experiments, E. coli inactivation reached 7 log with ozone, UV and available chlorine of 3 mg/L, 5 or 10 mJ/cm2 and 2.5 mg/L, respectively. On the basis of the results from the actual WRP, the estimated operating cost per unit for the disinfection systems is 0.065 CNY/t, which is economical for long-term operation.

Trihalomethane species model for drinking water supply systems

Despite the existence of significant knowedge on complex mechanisms of THM formation, a simple kinetic model to predict THM species concentration is not available, hindering application of knowlwdge for regulatory, monitoring and operational control. The parallel second order reaction (2R) model containing fast and slow reactants has been well established to describe the chlorine decay kinetics under distribution conditions. The proposed THM species model expands the 2R model by systematically incorporating the initial unproductive (not forming THM) chlorine consumption and assuming each THM species is formed at a fixed yield (µg-THM species/mg- productive chlorine consumption). The model concept is tested on 15 water samples that contain a wide range of dissolved organic carbon, specific UV absorbence, and bromide concentrations collected from Australia and US. In all samples, the model describes the THM species concentrations well (error < 3 µg/L in 84% of model estimates) as long as the chlorine profile is described accurately (R2 > 0.984). The model formulated from the minimum data (initial and two other data points of Cl2 and THM species) predicts the rest of concentrations of THM species from only chlorine measurements. To fully optimise the system or adopt in regulatory monitoring, the effect of changes due to bulk water quality, operational conditions and wall (and biofilm) effects on THM formation kinetics should be established. A similar concept could be extended to other DBP, but rigorous testing is needed.

Study on the removal of aesthetic indicators by ozone during advanced treatment of water reuse

Aesthetics and water quality are primary issues of concern for sustainable water reuse since aesthetically unpleasant color and odor are likely to induce public misgiving. This study utilizes aesthetic indicators and other bulk water quality parameters for evaluation. It is found that ozonation during advanced treatment processes in a full-scale water reclamation plant (WRP) could achieve satisfactory performance in decolorization and oxidation of aromatic and humic contents. As limited efficacy on odor removal was detected in the WRP, this study further researched the removal of the main odorant substances 2-methylisokanol (2-MIB) and geosmin (GSM) with different ozone dosage using solid-phase extraction (SPE) and gas phase mass spectrometry (GC–MS) techniques. According to the first-order reaction kinetics, it is inferred that competitive reactions during ozonation by organic matters and restricted CT values are major factors affecting the odor removal. As such, additional treatment approaches such as nanofiltration (NF) are suggested to be consider for aesthetic control towards sustainable and long-term reclaimed water use.

Comparison of micropollutants' removal performance between pre-ozonation and post-ozonation using a pilot study

Despite the strong oxidizing ability of ozone, pre-ozonation has seldom been employed for the purpose of micropollutant removal in drinking water utilities. In this paper, the possibility of using pre-ozonation instead of post-ozonation for the removal of micropollutants was explored because of the lower risk of forming carcinogenic bromate. A 1.0 m3/h pilot system was utilized to compare the efficacy of pre- and post-ozonation in the removal of bulk organic pollutants as well as micropollutants, including typical odor-causing compounds, pharmaceuticals, and typical pesticides, from one source water (Huangpu River) characterized by the occurrence of various micropollutants. Both pre-ozonation and post-ozonation could achieve similar water purification performance under an ozone dose of 1.5 mg/L, in terms of bulk water quality parameters like CODMn (66% in combination with biological activated carbon (BAC) treatment, compared to 62% with the pre-ozonation-BAC combination) or micropollutants including 27 pharmaceuticals (85% in combination with BAC compared to 87% with the pre-ozonation-BAC combination) and 25 pesticides (72% in combination with BAC compared to 61% with the pre-ozonation-BAC combination). Pre-ozonation exhibited slightly better odorant removal performance (100% in combination with BAC compared to 92% with the post-ozonation-BAC combination); however, post-ozonation generated approximately 6.0 μg/L bromate at an ozone dose of 2.0 mg/L, while pre-ozonation did not form bromate even at an ozone dose as high as 3.0 mg/L. So pre-ozonation in combination with BAC might be a solution for the removal of micropollutants from source water with high bromate formation risk. The results of this study will be helpful for the optimization of ozonation processes in the water supply industry.

Fate of sulfonamide resistance genes in estuary environment and effect of anthropogenic activities

With the exacerbating problem of antibiotic resistance, antibiotic resistance genes (ARGs) as emerging contaminants are found at elevated levels in inland aquatic environments, especially in regions of intensive agricultural and urban activity. However, little quantitative data exist on the migration and attenuation of ARGs in estuary ecosystem, which is central to predicting their fate after release into marine environment. Moreover, the relevance of multiple chemical contaminants and water quality constituents should be understood to amplify and attenuate antibiotic resistance levels. To determine the prevalence and examine the fate of sulfonamide ARGs (sul-ARGs) in two estuaries under different effects of anthropogenic activities, we analyzed the sul-ARGs (sul1, sul2, and sul3), class 1 integrons (int1), and bacterial biomass in surface water samples from Daliaohe and Liaohe river estuaries. We also evaluated five types of antibiotics, heavy metals, and various bulk water quality constituents. Results showed that sul-ARGs were widespread in Daliaohe and Liaohe river estuaries, but the distribution did not correlate with the concentration of sulfonamides. Significant reduction in the abundance of sul-ARGs was also observed with increased salinity. Nevertheless, the trend in the change of concentrations of sul-ARGs was different in the two estuaries. Statistical analysis of the results indicated that several metals were significantly and positively correlated with sul-ARGs. Pearson's correlation coefficients were higher than those determined between antibiotic residues and sul-ARGs. Furthermore, the relative abundance of sul-ARGs was significantly and positively correlated with the relative abundance of int1 which suggested that the propagation of sul-ARGs was facilitated by class 1 integrons in estuaries.

Hazardous events in membrane bioreactors – Part 1: Impacts on key operational and bulk water quality parameters

In this series of articles, the potential impacts of a number of operational ‘hazardous events’ on membrane bioreactors (MBRs) removal performance were investigated. The hazardous events assessed included salinity shock, 2,4-dinitrophenol (DNP) shock, ammonia shock, organic carbon shock, feed starvation, loss of power supply, loss of aeration, complete wash out of biomass, defective fibres, and physical membrane damage. This initial study focuses on the removal of key bulk water quality and operational parameters, i.e. changes in pH, turbidity, chemical oxygen demand (COD), dissolved organic carbon (DOC), biomass concentrations, capillary suction time (CST) and membrane fouling rate. DNP, salinity and organic carbon shock conditions were shown to significantly impact removal of organic matter (in terms of COD and DOC). These findings suggest that changes in COD and DOC concentrations were determined to be effective parameters for monitoring the impacts of these shock load events. Feed starvation significantly impacted biomass concentrations but the overall system performance remained relatively resilient, as it continued to achieve effective COD and DOC removals. The results from physical membrane damage experiment confirm that turbidity is an effective indicator for online monitoring of physical membrane damage. The results of this study can assist with validation of MBR processes.

Responses of Phanerochaete chrysosporium to Toxic Pollutants: Physiological Flux, Oxidative Stress, and Detoxification

The white-rot fungus Phanerochaete chrysosporium has been widely used for the treatment of waste streams containing heavy metals and toxic organic pollutants. The development of fungal-based treatment technologies requires detailed knowledge of the relationship between bulk water quality and the physiological responses of fungi. A noninvasive microtest technique was used to quantify real-time changes in proton, oxygen, and cadmium ion fluxes following the exposure of P. chrysosporium to environmental toxic (2,4-dichlorophenol and cadmium). Significant changes in H(+) and O(2) flux occurred after exposure to 10 mg/L 2,4-dichlorophenol and 0.1 mM cadmium. Cd(2+) flux decreased with time. Reactive oxygen species formation and antioxidant levels increased after cadmium treatment. Superoxide dismutase activity correlated well with malondialdehyde levels (r(2) = 0.964) at low cadmium concentrations. However, this correlation diminished and malondialdehyde levels significantly increased at the highest cadmium concentration tested. Real-time microscale signatures of H(+), O(2), and Cd(2+) fluxes coupled with oxidative stress analysis can improve our understanding of the physiological responses of P. chrysosporium to toxic pollutants and provide useful information for the development of fungal-based technologies to improve the treatment of wastes cocontaminated with heavy metals and organic pollutants.

Discoloration Material Accumulation in Water Distribution Systems

Despite a significant ongoing investment in asset renewal and rehabilitation and high compliance rates for drinking water quality standards, water companies continue to receive customer contacts relating to water quality, dominated by discoloration. This paper investigates the accumulation of material responsible for causing such discoloration in drinking water distribution systems from new field data. Engineering experience suggests that factors influencing this accumulation might include local pipe properties such as age, material, or diameter. On the basis of recent research, it also seems reasonable to expect hydraulic conditions and bulk water quality to be important. Results of extensive repeated flushing field trials in two representative distribution management areas (DMAs) over a two and a half year period are presented. Initial flushing suggested that the maximum thickness of discoloration material accumulated within the pipes was tentatively inversely proportional to the daily conditioning shear stress, in agreement with previous research, but independent of pipe material and/or diameter. An analysis of discoloration material from different strength layers, facilitated through stepped flushing, showed that the metal composition was uniform, and the process of accumulation simultaneously occurs across all strength characteristics. In plastic pipes, a limiting layer strength of 0.7 N/m2 was observed, above which significant additional discoloration material was not mobilized. Repeat flushing at different return intervals showed the accumulation rate of discoloration material in both DMAs to be consistent, within field-based experimental error, with an average of 0.0057 mm/month (95% confidence level of 0.0015). This rate was consistent across the different pipe materials, diameter, age, and hydraulic conditions within each DMA and between the two DMAs. Results from repeat flushing at increasing time intervals show that accumulation is a linear function of time; although, because of the uncontrolled nature of field work, this assertion is only definitive for five pipe lengths. From this, it is suggested that accumulation is primarily dependent on factors external to the DMA, and it is likely that this is dominated by the supplied water quality. This accumulation rate might seem small; however, after only 43 days of accumulation, the mobilization of the total accumulated volume of material into one pipe volume of a 140 mm pipe would be sufficient to exceed UK regulatory limits of 4 NTU for turbidity.

Attenuation of contaminants of emerging concern during surface-spreading aquifer recharge

The attenuation of a diverse suite of contaminants of emerging concern (CECs) and bulk water quality changes was evaluated at a surface-spreading aquifer recharge operation across a detailed subsurface profile (9 locations), representing both short- and long-travel times (10 h to 60 days). Seventeen CECs were detected in the recharge basin and the concentrations of all were reduced during soil aquifer treatment (SAT), with 11 of the target compounds attenuated by > 80% after 60 days of travel time. Select CECs (atenolol, gemfibrozil, N, N-diethly-3-methylbenzamide, meprobamate, tris(2-chloroethyl)phosphate, and primidone) and bulk water organic-carbon measurements (total organic carbon, biodegradable organic carbon, size-exclusion chromatography and fluorescence excitation–emission matrices) were identified as monitoring parameters that can be used to assess SAT performance at surface-spreading operations.

Tet and sul Antibiotic Resistance Genes in Livestock Lagoons of Various Operation Type, Configuration, and Antibiotic Occurrence

Although livestock operations are known to harbor elevated levels of antibiotic resistant bacteria, few studies have examined the potential of livestock waste lagoons to reduce antibiotic resistance genes (ARGs). The purpose of this study was to determine the prevalence and examine the behavior of tetracycline [tet(O) and tet(W)] and sulfonamide [sul(I) and sul(II)] ARGs in a broad cross-section of livestock lagoons within the same semiarid western watershed. ARGs were monitored for one year in the water and the settled solids of eight lagoon systems by quantitative polymerase chain reaction. In addition, antibiotic residues and various bulk water quality constituents were analyzed. It was found that the lagoons of the chicken layer operation had the lowest concentrations of both tet and sul ARGs and low total antibiotic concentrations, whereas sul ARGs were highest in the swine lagoons, which generally corresponded to the highest total antibiotic concentrations. A marginal benefit of organic and small dairy operations also was observed compared to conventional and large dairies, respectively. In all lagoons, sul ARGs were observed to be generally more recalcitrant than tet ARGs. Also, positive correlations of various bulk water quality constituents were identified with tet ARGs but not sul ARGs. Significant positive correlations were identified between several metals and tet ARGs, but Pearson's correlation coefficients were mostly lower than those determined between antibiotic residues and ARGs. This study represents a quantitative characterization of ARGs in lagoons across a variety of livestock operations and provides insight into potential options for managing antibiotic resistance emanating from agricultural activities.

Quantitative Structure−Property Relationship for Predicting Chlorine Demand by Organic Molecules

Conventional methods for predicting chlorine demand (HOCl(dem)) due to dissolved organic matter (DOM) are based on bulk water quality parameters and ignore structural features of individual molecules that may better indicate reactivity toward the disinfectant. The Quantitative Structure-Property Relationship (QSPR) modeling approach can account for structural properties of individual molecules. Here we report a QSPR for HOCl(dem) based on eight constitutional descriptors. Model compounds with HOCl(dem) ranging from 0.1 to 13.4 mol chlorine per mole compound were divided into a calibration and cross-validation data set (N = 159) and an external validation set (N = 42). The QSPR was calibrated using multiple linear regression in a 5-way leave-many-out approach and has average R(2) = 0.86 and standard error of regression (StdE(reg)) = 1.24 mol HOCl per mole compound and p < 0.05. Internal cross-validation has average q(2) = 0.85 and the external validation has q(2) = 0.88, indicating a robust model. The leverage of 7 of 42 compounds in the external validation data set exceeded the critical value, suggesting that these compounds may be overextrapolated. However, root-mean-square error of prediction in the external validation was 1.17 mol HOCl per mole compound, and all compounds were predicted with +/-2.5 standardized residuals (Sresid). Application of the QSPR to model structures of NOM predicts HOCl(dem) comparable to reported measurements from natural water treatment.

Managing sewer solids for the reduction of foul flush effects – Forfar WTP

In times of high sewer flow, conditions can exist which enable previously deposited material to be re-entrained back into the body of the flow column. Pulses of this highly polluted flow have been recorded in many instances at the recently constructed wastewater treatment plant (WTP) in Forfar, Scotland. Investigations have been undertaken to characterise the incoming flows and to suggest remedial measures to manage the quality fluctuations. Initial visits to the works and incoming pipes indicated a high degree of sediment deposition in the two inlet pipes. Analyses were carried out and consequently, changes to the hydraulic regime were made. Measurements of sediment level, sediment quality, wall slime and bulk water quality were monitored in the period following the remedial works to observe any improvements. Dramatic alterations in each of the determinands measured were recorded. Analyses were then undertaken to determine long term sediment behaviour and to assess the future usefulness of existing upstream sediment traps. It was concluded that with proper maintenance of the traps, the new hydraulic regime is sufficient to prevent further significant build up of sediment deposits and reduce impacts on the WTP. Further investigations made by North of Scotland Water Authority highlighted trade inputs to the system which may also have contributed to the now managed foul flush problem.

Relationship between population dynamics of nitrifiers in biofilms and reactor performance at various C:N ratios

The relationship between time dependent population dynamics of nitrifiers and heterotrophs in undefined mixed-population biofilms and their nitrification efficiency was experimentally investigated at various C:N ratios of feed solutions. Five types of biofilms were cultured in partially submerged rotating biological contactors (RBC's) at different C:N ratios and were used as test materials. The results indicated that initial microbial composition in the biofilms and substrate composition (e.g. C:N ratio) strongly influenced the later population dynamics and the nitrification efficiency. Higher influent C:N ratio retarded accumulation of nitrifying bacteria, especially NO 2-oxidizers, resulting in a considerably long start-up period for complete and stable nitrification due to competition for dissolved oxygen and space in the biofilm. Furthermore, a start-up inoculum was very important to keep start-up time of nitrification to a minimum. Time-dependent population dynamics in the biofilms reflected well the bulk water quality and microbial community structure in the bulk liquid. These results suggest that the structure of microbial community in the biofilm can be predicted from monitoring the water quality and microbiology of the bulk liquid. Physiologically inactive cells in the biofilm were determined by an INT dehydrogenease assay. These cells gradually accumulated up to about 30% of the total bacterial population within the biofilms. The results of this study will provide a rational basis for developing and controlling desired biofilm population dynamics to maximize nitrification efficiency of wastewater biofilms

Satellite observations of ocean colour

Ocean colour is unique among the properties of the sea that can be measured from satellites because visible wavelength radiation penetrates below the surface skin and contains direct information about the bulk water quality in the upper few metres of the sea. With reference to Nimbus czcs and Landsat MSS data, this review examines three aspects of ocean-colour monitoring: the removal of atmospheric effects, which make up a large proportion of the visible signal reaching the satellite; the calibration of the ocean colour signal in terms of more useful ocean parameters such as sediment load, chlorophyll concentration, water depth or the depth of the euphotic zone; and the potential applications of colour-monitoring satellites to oceanography. Algorithms for atmospheric correction are now well developed, but calibration for chlorophyll or sediment is less certain, particularly where inorganic sediments or land-derived yellow substance, as well as the local phytoplankton population, are present in the sea. Oceanographic applications include the estimate of total productivity, the identification of blooms, and the location of productive areas to assist ship surveys. The greatest potential for satellite observations of ocean colour may lie in the synoptic spatial information contained in the images, but this awaits serious exploitation by dynamical oceanographers.