Sorption of Pb(II), Cr(III), Cu(II), As(III) to peat, and utilization of the sorption properties in industrial waste landfill hydraulic barrier layers

In this study, removal of suspended solids (SS) and turbidity from marble processing wastewaters by electrocoagulation (EC) process were investigated by using aluminium (Al) and iron (Fe) electrodes which were run in serial and parallel connection systems. To remove these pollutants from the marble processing wastewater, an EC reactor including monopolar electrodes (Al/Fe) in parallel and serial connection system, was utilized. Optimization of differential operation parameters such as pH, current density, and electrolysis time on SS and turbidity removal were determined in this way. EC process with monopolar Al electrodes in parallel and serial connections carried out at the optimum conditions where the pH value was 9, current density was approximately 15 A/m², and electrolysis time was 2 min resulted in 100% SS removal. Removal efficiencies of EC process for SS with monopolar Fe electrodes in parallel and serial connection were found to be 99.86% and 99.94%, respectively. Optimum parameters for monopolar Fe electrodes in both of the connection types were found to be for pH value as 8, for electrolysis time as 2 min. The optimum current density value for Fe electrodes used in serial and parallel connections was also obtained at 10 and 20 A/m², respectively. Based on the results obtained, it was found that EC process running with each type of the electrodes and the connections was highly effective for the removal of SS and turbidity from marble processing wastewaters, and that operating costs with monopolar Al electrodes in parallel connection were the cheapest than that of the serial connection and all the configurations for Fe electrode.     

Suspended solids transport in the regulated River Blithe,Staffordshire, U.K.

Suspended solids concentrations and turbidity were monitored on the regulated River Blithe at two sites downstream of the reservoir for a period of 18 months. Changes in the suspended solids loads transported and the nature of the material in suspension are related to dam overspill and tributary flood events. A hysteretic relationship between suspended solids concentrations and discharge is characteristic of both sites, sediment supply being limited within the regulated river. Downstream of the dam, rapid bank erosion occurred on meander bends but the suspended solids loads transported by the regulated river relate more to the resuspension and transport of tributary injected sediments and scouring of a dense periphyton. Close to the dam, fine biogenic matter dominated the seston, which scanning electron microscopy revealed to contain algal fragments and inorganic diatom frustules, but downstream, tributary-derived minerogenic particles were dominant.     

Ozonation at Belle Glade,Florida : A Case History

In October 1984, the city of Belle Glade, FL installed a two-stage ozonation process for the treatment of lake water high in organics (av TOC 30 mg/L; up to 75 mg/L), high in color (av 100 color units; up to 500), and high in THM concentrations, at times nearly 1,000 μ/L. The new treatment process applied 3 mg/L of ozone to the raw water ahead of the flash mix basin, lime softening, alum and polymer coagulation, clarification, recarbonation, and addition of 3 mg/L ozone prior to filtration. Post-chlorination then produced distribution system THM concentrations averaging 124 μg/L. Distribution of THMs shifted from 85% chloroform by the original process to 40% after adoption of ozonation, the balance comprising brominated species (but not bromoform).

In 1987, the treatment process was modified by adding chlorine and ammonia at the outlets of the pre- and intermediate-stages of ozonation and abandoning free chlorination. This has further reduced the distribution system THM levels to 20-30 μg/L. Filtered water turbidity and color have been improved. The use of chloramines after ozonation controls the nuisance aquatic growths in the clarifiers and recarbonation basins (caused by ozonation alone), and produces a combined chlorine residual which can be maintained throughout the distribution system. Periodic use of free chlorine in the distribution system is required to prevent elevated heterotrophic plate counts and the formation of excessive concentrations of nitrite ion due to biological regrowth and nitrification.     

Numerical Study of Turbidity Currents with Sudden-Release and Sustained-Inflow Mechanisms

A well-tested numerical model based on the Reynolds averaged Navier–Stokes equations with k-ε turbulence closure is further validated against three groups of experimental data on lock-exchange gravity flows. The model is then applied to study larger-scale turbidity currents with sudden-release and/or sustained inflow mechanisms. At the field-scale, sudden-release turbidity currents are found to be essentially unsteady with depth-averaged flow variables varying with time and distance from the upstream boundary. Turbidity currents with sustained inflows reach a quasi-equilibrium state in the body of the current. The simulation of a turbidity current initiated by sudden-release and then fed by sustained inflow reveals that, initially, two bore heads appear in the current with the second bore head resulting from sustained inflow and eventually catches up with the first one. Model results show that, depending on onset mechanism and slope, if the erosion rate of sediment exceeds the deposition rate, turbidity currents at the field scale can experience self-acceleration, a process predicted earlier by theory but not demonstrated in laboratory experiments.     

核电站大修卸料前反应堆水池水质浑浊原因分析

介绍了某核电站大修卸料前反应堆水池浑浊事件,从反应堆水池浑浊前操作、引起水质浑浊的物质来源、污染过程等方面对浑浊原因进行了分析,介绍了处理措施。     

强化过滤减少滤池出水颗粒数的生产性试验研究

应用颗粒计数仪对强化过滤技术降低滤池出水浊度进行了研究.研究表明,颗粒计数能更准确反映水中的悬浮颗粒情况,强化过滤主要去除粒径为2μm的颗粒;投加聚氯化铝(PAC)较活化硅酸能更有效地降低浊度和颗粒数;在反冲洗水中投加PAC可有效降低滤池初期出水浊度和颗粒数.而生产性试验结果表明,投加2.5～3 mg/L的PAC,出水浊度最低,且不会影响过滤周期.投加适当剂量的PAC不会导致出水的铝超标.     

Heatwaves and storms contribute to degraded water quality conditions in the nearshore of Lake Ontario

As extreme climatic events, such as heatwaves and storms, become more frequent in response to changing climates, understanding the role climatic events play on water quality is essential. Here, we use water quality monitoring data collected from the nearshore of Lake Ontario between 2000 and 2018 to ask: i) which sites in the nearshore of Lake Ontario have statistically extreme water quality conditions?; ii) do water quality conditions differ in extreme versus non-extreme climate years?; and iii) what are the significant antecedent extreme weather drivers of water quality in the nearshore of Lake Ontario? Three sites with the highest chlorophyll a concentrations and eutrophic conditions, two of which are in Areas of Concern, exhibited the strongest responses to climate extremes. Antecedent weather conditions explained 87.2% of the variation in extreme chlorophyll a concentrations. In particular, warmer temperatures and heatwaves corresponded with statistical extremes in chlorophyll a concentrations. Precipitation accounted for 35.5% of the variation in extreme conditions of turbidity, including storm events the day prior to sampling. When considering site-specific extreme conditions, antecedent weather conditions explained 66.8% of the variation in turbidity. We illustrate the strong role that heatwaves and storm events play on spatial and temporal patterns in extreme water quality conditions, highlighting the importance of incorporating climate change adaptation plans into ecosystem management strategies to preserve water quality in the highly important and iconic nearshore regions of the Laurentian Great Lakes.     

Modelling the propagation of turbid density inflows into a stratified lake: Daecheong Reservoir, Korea

Many reservoirs and associated downstream ecosystems located in the Asian monsoon climate region are under increased pressure from the long-term negative effects of turbid flood runoff. Despite the ubiquitous use of turbidity (C_T) as a barometer of water quality and environmental “health”, C_T modelling studies have been rare due to lack of detailed experimental data required for validation. This study explored the fate and transport of a turbid density flow entering a stratified reservoir (Daecheong Reservoir, Korea) through application of a coupled three-dimensional (3D) hydrodynamic and particle dynamics model and subsequent validation of the predictions against an extensive data-set collected during the flood season of 2004. The turbidity model simulated multiple size groups of suspended sediment (SS) and used site-specific SS–C_T relationships to convert between field measurements (C_T) and model state variables (SS). The model showed good performance in reproducing the reservoir thermal structure, flood propagation dynamics and the magnitude and distribution of turbidity in the reservoir. The turbidity modelling framework developed in this study can be adopted within a real-time management system for forecasting of turbidity and to support adaptive control of withdrawal facilities in reservoirs that suffer from turbid flood runoff.     

Predicting safety and quality parameters for UHT-processed milks

A spreadsheet was developed to evaluate safety and quality parameters for milks subjected to different heating and cooling profiles and holding time conditions in a continuous heat exchanger. Safety parameters evaluated were lethality ( Fo ) and microbial inactivation ( B *) values; quality parameters were chemical change ( C *), thiamin loss, lactulose formation, Maillard browning and hydroxymethylfurfural (HMF) formation. The spreadsheet was used to predict these parameters for a pilot plant, heating milks at 120–150°C for 4, 27 and 58 s, using its heating and cooling profiles. Milks were processed in the same plant at these conditions and a selection of the milks were analysed to establish the validity of the spreadsheet. All samples with a C * value < 3 gave a positive Aschaffenburg turbidity. The activation energy that gave the best agreement between the predicted and experimental results for lactulose was found to be 122 kJ/mol. One set of optimized conditions for this product was 135°C for 10 s, giving B * = 1.24 and C * = 0.55. This milk was compared with two others and its sensory characteristics were similar to that with a C * of 1.5 but different to that with a C * value of 6. Browning was only found to be noticeable in the most severely heat-treated sample immediately after processing, but would become apparent on storage at 30°C and above. The spreadsheet is useful for comparing the characteristics of products from plants with different heating profiles or as a means for optimizing UHT plant performance where the heating and cooling rates are fixed.     

Interactions between protein fining agents and proanthocyanidins in white wine

A comparative fining trial was conducted in a laboratory scale to study the influence of protein fining agents on proanthocyanidins, colour and browning potential of white wine. The monomeric flavanols were significantly depleted by casein, and gelatine with low molecular weight (MW) distribution, and isinglass obtained from fish swim bladder (MW > 94.0, containing some bands in the range 94.0–43.0 and at 20.1 kDa). However, the other gelatines and isinglass with a MW polydispersion below 20.1 kDa did not interact significantly (P < 0.05) with these compounds. In contrast, the oligomeric compounds were not decreased by swim bladder isinglass. It was also observed that neither of the isinglasses decreased the polymeric flavanols significantly (P < 0.05). Although casein and potassium caseinate had similar MW distributions and isoelectric points, potassium caseinate decreased the polymeric flavanols, whereas casein did decrease monomeric, oligomeric and polymeric flavanols significantly (P < 0.05). The degree of polymerisation of polymeric proanthocyanidins that remained in the fined wine decreased significantly (P < 0.05) after addition of protein fining agents except when potassium caseinate was used. Casein, potassium caseinate and swim bladder isinglass induced a significant (P < 0.05) decrease in wine colour (A_420nm), a decrease in browning potential and a decrease in turbidity.