Semi‐Micro Reflux Procedure for Minimization of Chloride Interference by COD Determination

In this study, a semi‐micro procedure for the COD (Chemical Oxygen Demand) was undertaken to allow the measurement of effluent samples with a high chloride content. It was found that the COD values for standard and effluent samples, corresponded closely to those obtained using the standard method of Burns and Marshall. When the method was applied to samples of industrial wastewater, with a very high chloride content, the recommended procedure proved to be accurate and precise, with RSDs of 6% and 4.3% for the standard and effluent solutions, respectively. The required amount of hazardous reagents was similar to that found in the standard closed reflux method. It was also possible to determine the total amount of oxidized halides. The use of this low‐cost, laboratory‐made system made it unnecessary to acquire an expensive, imported analytical system, while maintaining a high level of accuracy in the determinations.     

Bestimmung eines Gruppenparameters für organische Halogenverbindungen in Wasserproben mit hohen Salzgehalten unter Verwendung von XAD-4-Harz

Determination of a Group Parameter for Organic Halogen Compounds in High Salt-laden Water Samples Using XAD-4 Resin Concerning the often discussed ‘chloride error’ in AOX determination, a method is described with allows the determination of the group parameter organic halogen compounds (OX) for chloride concentrations more than 1 g/L. In opposite to the standard method DIN 38409 part 14, no chloride influence up to a concentration of 10 g/L in real water samples occurs. The basis of the method is the adsorption of the organic compounds from the water sample on XAD-4 resin, a nonpolar copolymer of styrene and divinylbenzene. The organic compounds are concentrated on the XAD-4 resin conditioned with methanol. After the enrichment step, the adsorption columns are treated with sodium nitrate solution. Model experiments with p-chlorophenol and chloride concentrations of 50 g/L showed the effectiveness of this method. The loaded and washed adsorption columns are first eluated with acetone and then with ethyl acetate. Quantification of the OX compounds in the eluates is carried out by microcoulometric detection after combustion in a furnace equipped with a special injector for eluates. For optimal work, the instrument was modified and improved. The presented method was developed on model samples and tested on different real samples.     

Treatment of Synthetic Olefin Plant Wastewater at Various Salt Concentrations in a Membrane Bioreactor

The objective of this study was to investigate the effect of salt concentration on performance of a membrane bioreactor (MBR) for treating an olefin plant wastewater. For this purpose, a lab‐scale submerged MBR with a flat‐sheet ultrafiltration membrane was used for treatment of synthetic wastewater according to oxidation and neutralization unit of olefin plant. The synthetic wastewater was adjusted to have 500 mg/L chemical oxygen demand (COD). Trials on different concentrations of sodium sulfate (Na₂SO₄) (0–20 000 ppm) in the feed were conducted under aerobic conditions in the MBR. The results showed that increasing the salt concentrations causes an increase in the effluent COD, phenol, and oil concentrations. These results are due to reduction of the membrane filtration efficiency and also decline in the microbial activity that it is indicated by decreasing the sOUR in MBR. But in all the trials, the effluent COD and oil concentration was well within the local discharge limit of 100 and 10 mg/L, respectively. These results indicate that the MBR system is highly efficient for treating the olefin plant wastewater, and although high salt concentrations decreased organic contaminant removal rates in the MBR, the effluent still met the discharge limits for treating the olefin plant wastewater.     

Amelioration of Carbon Removal Prediction for an Activated Sludge Process using an Artificial Neural Network (ANN)

A dynamic simulation model of the Ankara central wastewater treatment plant (ACWTP) was evaluated for the prediction of effluent COD concentrations. Firstly, a mechanistic model of the municipal wastewater treatment process was developed based on Activated Sludge Model No. 1 (ASM1) by using a GPS‐X computer program. Then, the mechanistic model was combined with a feed‐forward back‐propagation neural network in parallel configuration. The appropriate architecture of the neural network models was determined through several iterative steps of training and testing of the models. Both models were run with the data obtained from the plant operation and laboratory analysis to predict the dynamic behavior of the process. Using these two models, effluent COD concentrations were predicted and the results were compared for the purpose of evaluation of treatment performance. It was observed that the ASM1 ANN model approach gave better results and better described the operational conditions of the plant than ASM1.     

Profiles of chloride and stable isotopes in pore-water obtained from a 2000 m-deep borehole through the Mesozoic sedimentary series in the eastern Paris Basin

Water stable isotopes and chloride profiles in pore-water through more than 800 m of sediments were obtained from a 2000 m-deep borehole (EST 433) drilled by Andra in the eastern Paris Basin. Vapour exchange method and aqueous leaching were used to obtain the stable isotope and chloride concentrations of pore-water from 24 rock samples. Petrophysical measurements included water contents, grain densities and porosities of the studied formations. Pore-water and some groundwater samples collected during the drilling are mainly of meteoric origin: they plot near the Global Meteoric Water Line, distributed between heavy-isotope depleted Oxfordian groundwater and enriched Triassic groundwater, in good agreement with previous data. The δ²H and δ¹⁸O values describe curved profiles in the Callovo-Oxfordian formation, and show an increase with depth below this formation (Dogger and Liassic). Similar trends were observed for the chloride concentrations, except in the Liassic formation where they are more or less constant. The low chloride concentrations in the basal Jurassic layers indicate that the source of salinity to the Dogger aquifer is likely the middle Liassic formation and not the Triassic salt as previously suggested. A preliminary modelling exercise showed that currently available diffusion parameters (diffusion coefficients and accessible porosities) might be used to properly simulate these exchanges for deuterium. This is not the case for chloride, perhaps because the used values for anion accessible porosity were not relevant and/or the applied modelling conditions were unsuitable.     

Impact of Turbidity on TCE and Degradation Products in Ground Water

Elevated particulate concentrations in ground water samples can bias contaminant concentration data. This has been particularly problematic for metal analyses where artificially increased turbidity levels can affect metals concentrations and confound interpretation of the data. However, few studies have been conducted to determine the impact of particulates on trichloroethylene (TCE), cis-dichloroethylene (c-DCE), and vinyl chloride concentrations.
Laboratory batch studies and field investigations were conducted to evaluate the effects of suspended solids on VOC concentrations in ground water samples analyzed by purge-and-trap gas chromatography. Three different solids were used to assess the effects of suspended particulates. The solids were aquifer material from a field site in North Carolina and two reference clay minerals (kaolinite and Namontimorillonite). During the laboratory portion of this study, the solids were used to determine effects on TCE concentrations under controlled laboratory conditions.
The same solids were used in a field study to compare the laboratory results with field results. Solids were added to the sample vials prior it) sample collection to intentionally increase turbidity levels in the water samples. Results of the study indicate essentially no decrease in TCE, c-DCH, or vinyl chloride concentrations due to increased turbidity levels.     

计算地震初至波视出射角方法

在理论上证明了使用地震初至波位移、速度或加速度记录资料在时间域或频率域计算视出射角,使视出射角计算不受位移记录及时间域限制。在干扰信号频率段与有效信号频率段存在差异时分别在时间域和频率域进行了视出射角计算,结果表明在频率域中得到的视出射角基本与理论值相符,与方位角无关;而在时间域中获得的视出射角与理论值波动很大。应用实际地震波记录资料计算了不同台站的视出射角,其结果同样表明在频率域中获得的视出射角比时间域视出射角更加稳定和可信。     

Stochastic modeling applications for the prediction of COD removal efficiency of UASB reactors treating diluted real cotton textile wastewater

A three-layer Artificial Neural Network (ANN) model (9:12:1) for the prediction of Chemical Oxygen Demand Removal Efficiency (CODRE) of Upflow Anaerobic Sludge Blanket (UASB) reactors treating real cotton textile wastewater diluted with domestic wastewater was presented. To validate the proposed method, an experimental study was carried out in three lab-scale UASB reactors to investigate the treatment efficiency on total COD reduction. The reactors were operated for 80 days at mesophilic conditions (36–37.5°C) in a temperature-controlled water bath with two hydraulic retention times (HRT) of 4.5 and 9.0 days and with organic loading rates (OLR) between 0.072 and 0.602 kg COD/m³/day. Five different dilution ratios of 15, 30, 40, 45 and 60% with domestic wastewater were employed to represent seasonal fluctuations, respectively. The study was undertaken in a pH range of 6.20–8.06 and an alkalinity range of 1,350–1,855 mg/l CaCO₃. The concentrations of volatile fatty acids (VFA) and total suspended solids (TSS) were observed between 420 and 720 mg/l CH₃COOH and 68–338 mg/l, respectively. In the study, a wide range of influent COD concentrations (COD_i) between 651 and 4,044 mg/l in feeding was carried out. CODRE of UASB reactors being output parameter of the conducted anaerobic treatment was estimated by nine input parameters such as HRT, pH, COD_i concentration, operating temperature, alkalinity, VFA concentration, dilution ratio (DR), OLR, and TSS concentration. After backpropagation (BP) training combined with principal component analysis (PCA), the ANN model predicted CODRE values based on experimental data and all the predictions were proven to be satisfactory with a correlation coefficient of about 0.8245. In the ANN study, the Levenberg-Marquardt Algorithm (LMA) was found as the best of 11 BP algorithms. In addition to determination of the optimal ANN structure, a linear-nonlinear study was also employed to investigate the effects of input variables on CODRE values in this study. Both ANN outputs and linear-nonlinear study results were compared and advantages and further developments were evaluated.     

Analysis of Physical and Chemical Parameters for Discrimination of Water Origin in a Hydroelectric Reservoir

Seventeen physical and chemical parameters were obtained from a hydroelectric reservoir located in a tropical region in the south of Brazil. Multivariate Principal Component Analysis (PCA) and Hierarchical Group Analysis (HGA) were used to identify the parameters discriminating the origin of water from the Tibagi and the Primeiro de Maio River, after it has passed the mixing region. The study was conducted during the dry and rainy seasons in July 2002 and February 2003 at three depths and three sampling sites located 0, 5, and 10 km away from the mixing region. The statistical methods showed to be appropriate for identifying the contribution of each tributary in the water mixing site of a complex water system. The most important discriminating parameter was the absorbance relation A(253 nm)/A(203 nm), followed by the concentrations of Fe(III), Mn(III), and Ni(II). An anthropogenic interference was found in the reservoir due to high Ni(II) and orthophosphate concentrations caused by a nearby town sewage discharge. The interference was more important during the dry periods due to the lower dispersion of the pollutants. Urgent initiatives should be taken from the state government to build treatment stations for the wastewater of the small cities around the Capivara hydroelectric reservoir to prevent the drinking water quality from deteriorating.     

Sonochemical Degradation of Pharmaceutical Wastewater

This study presents the influence of the addition of additives such as activated carbon, carbon tetra chloride, hydrogen peroxide, and potassium dichromate on ultrasonic reduction of pharmaceutical wastewater chemical oxygen demand (COD) under laboratory conditions. The addition of activated carbon increased the % COD reduction whereas the combined addition of activated carbon and H₂O₂/CCl₄/K₂Cr₂O₇ was found to show higher reduction. Among the various combinations investigated, the combined addition of activated carbon and CCl₄ was found to be the best combination. However, the environmental and health problems associated with these chemicals limit the applicability of the process in an industrial level. Further investigation with this system showed that the initial pH and initial COD have significant influence on the removal rate. The data obtained were fitted with first order and Langmuir–Hinshelwood kinetic models. The values of the rate constants obtained indicated that the pharmaceutical wastewater can be treated efficiently by the proposed methods.     

Removal of Organic Pollutants from Wastewater Using Wood Fly Ash as a Low‐Cost Sorbent

In this study, untreated and treated wood fly ash (WA) was used as a low‐cost sorbent in batch sorption tests to investigate the removal of organic pollutants from a real wastewater generated by cleaning/washing of machinery in a wood‐laminate floor industry in Sweden. The experiments focused on the effect of the WA dosage and particle size on the removal efficiency for organic compounds. With a WA dosage of 160 g L^?1 and a particle size less than 1 mm, the reductions of chemical oxygen demand (COD), biologic oxygen demand, and total organic carbon were 37 ± 0.4, 24 ± 0.4, and 30 ± 0.3%, respectively. Pre‐treatment of WA with hot water improved the COD removal efficiency by absorption from 37 ± 0.4 to 42 ± 1.6% when the same dosage (160 g L^?1) was applied. Sorption isotherm and sorption kinetics for COD using untreated WA can be explained by Freundlich isotherm and pseudo‐second‐order kinetic models. Intra‐particle diffusion model indicates that pore diffusion is not the rate‐limiting step for COD removal. Based on the experimental data, WA could be used as an alternative low‐cost sorption media/filter for removal of organic compounds from real industrial wastewater.     

Simultaneous Organic Matter and Nitrogen Removal from Piggery Slaughterhouse Wastewater Using Bioaugmented Gaslift Membrane Bioreactor

A single bioaugmentation reactor and a side-stream gaslift membrane bioreactor combined with bioaugmentation are conducted to treat real wastewater from a centralized piggery slaughterhouse in Vietnam. The bioaugmented reactor is inoculated with heterotrophic microorganisms (Bacillus sp.) isolated from piggery slaughterhouse wastewater. The results of a single bioaugmentation experiment show high removal efficiency of chemical oxygen demand (COD) (84.8%–97.5%) and total nitrogen (TN) (69.9%–87.2%) at loading rates of 1.28–3.89 and 0.14–0.37 kg m⁻³ d⁻¹, respectively. The combined system demonstrates a significantly higher TN removal efficiency (89.0%–96.1%) (p < 0.001), more stable flux (36.0–38.4 L m⁻² h⁻¹), and transmembrane pressure (0.95–1.05 bar), and better capacity of separation of solid–liquid phases compared to the single bioaugmentation. High COD and TN removal efficiency is possibly due to assimilation and simultaneous nitrification and denitrification processes. The results of this study also indicate the feasibility and propitious efficiency of the bioaugmented gaslift membrane bioreactor for piggery slaughterhouse wastewater treatment.     

Mixture model based multivariate statistical analysis of multiply censored environmental data

Environmental data are commonly constrained by a detection limit (DL) because of the restriction of experimental apparatus. In particular due to the changes of experimental units or assay methods, the observed data are often cut off by more than one DL. Measurements below the DLs are typically replaced by an arbitrary value such as zeros, half of DLs, or DLs for convenience of analysis. However, this method is widely considered unreliable and prone to bias. In contrast, maximum likelihood estimation (MLE) method for censored data has been developed for better performance and statistical justification. However, the existing MLE methods seldom address the multivariate context of censored environmental data especially for water quality. This paper proposes using a mixture model to flexibly approximate the underlying distribution of the observed data due to its good approximation capability and generation mechanism. In particular, Gaussian mixture model (GMM) is mainly focused in this study. To cope with the censored data with multiple DLs, an expectation–maximization (EM) algorithm in a multivariate setting is developed. The proposed statistical analysis approach is verified from both the simulated data and real water quality data.     

An Automatic Method of Direct Interpretation of Residual Gravity Anomaly Profiles due to Spheres and Cylinders

We have developed a least-squares minimization approach to determine the depth and the amplitude coefficient of a buried structure from residual gravity anomaly profile. This approach is basically based on application of Werner deconvolution method to gravity formulas due to spheres and cylinders, and solving a set of algebraic linear equations to estimate the two-model parameters. The validity of this new method is demonstrated through studying and analyzing two synthetic gravity anomalies, using simulated data generated from a known model with different random error components and a known statistical distribution. After being theoretically proven, this approach was applied on two real field gravity anomalies from Cuba and Sweden. The agreement between the results obtained by the proposed method and those obtained by other interpretation methods is good and comparable. Moreover, the depth obtained by the proposed approach is found to be in very good agreement with that obtained from drilling information.     

Dynamic Treatment Response of Olive Mills Wastewater Using Series of Adsorption Steps

Olive mills wastewater (OMW) is a critical environmental problem in the Mediterranean area due to its extremely high levels of COD and phenols. In this study, a group of adsorption experiments were conducted to investigate the dynamic response of the pH, COD, phenols, TSS, TDS, and TS concentrations of pretreated OMW, using different concentrations of activated carbon as adsorbent. The pretreatment included sedimentation and filtration of OMW. The pretreated OMW was then subjected to adsorption. A series of adsorption steps in stirred batch vessels were studied, namely, one stage, two‐stage countercurrent, and three‐stage countercurrent adsorption systems. A combined two‐ two‐stage countercurrent adsorption steps were also studied. Experimental results showed that such treatment protocols were promising. For example, a treatment protocol composed of a three‐stage countercurrent adsorption process using activated carbon of concentration of 24 g/L of OMW was able to reduce the COD from 60 000 mg/L down to 22 300 mg/L, while phenols were reduced from 450 to 15 mg/L.     

Characteristics of organic matter as indicators of pollution from small‐scale livestock and nitrate contamination of shallow groundwater in an agricultural area

The main purpose of this study was to examine the hydrogeochemical factors leading to nitrate contamination of shallow groundwater in an agricultural area. Another purpose was to identify relationships between variations in organic matter levels (as estimated by the BOD and COD parameters) of groundwater that transports effluent from small‐scale livestock holdings. Major cations, anions, BOD and COD of organic matter and total coliforms were analysed. It was found that groundwaters beneath cultivated areas and areas carrying livestock had higher concentrations of calcium, nitrate and chloride than did freshwater. Above all, the nitrification process increased concentrations of nitrate. Nitrate levels were depressed in some places where the groundwater was low in dissolved oxygen. Groundwaters affected by livestock activities showed high concentrations of organic matter (BOD, COD) and high microbial concentrations (as indicated by total coliforms). The COD/BOD ratio increased in the downward direction. It was inferred that this was due to the faster loss of easily biodegradable organic matter compared with non‐biodegradable organic matter proceeding away from a discharge. Accordingly, it is possible to trace effluent in a small area back to a point source by monitoring the COD/BOD ratio of groundwater. Copyright © 2003 John Wiley & Sons, Ltd.     

The Effect of Three Drilling Fluids on Ground Water Sample Chemistry

Three monitoring wells were installed in borings that were constructed using water-based drilling fluids containing either (1) guar bean, (2) guar bean with breakdown additive, or (3) bentonite. These fluids were selected to observe their effect on the chemistry of subsequent water samples collected from the wells. The wells were installed to depths of 66 feet, 100.5 feet and 103 feet, respectively, in fine-to-medium sand and gravel outwash deposits near Antigo, Wisconsin. Drilling fluids were necessary to maintain an open borehole during well construction through strata containing cobbles and boulders.
The bentonite and guar drilling fluids caused temporarily elevated concentrations of chemical oxygen demand (COD) in ground water samples collected from the monitoring wells. Using standard development, purging and sampling procedures, elevated COD concentrations persisted for about 50 days for the well bored with the guar-with-additive fluid, 140 days for the bentonite well and 320 days for the guar well. Unfiltered ground water samples for all wells had greater concentrations of COD than samples filtered through a 0.45 micron filter. Sulfate concentrations also decreased with time in the guar-with-additive well and bentonite well, but not in the guar well.
The elevated COD concentrations are attributed to the large concentrations of oxidizable carbon present in the guar bean drilling fluid and in the organic polymers present in the bentonite drilling fluid. Well development and purging procedures, including borehole flushing, surging, bailing and/or chemically induced viscosity breakdown of the guar mud decreased the time before background conditions were achieved. Future research should evaluate the physical and geochemical interaction of different drilling fluid compositions with a variety of geologic matrices and drilling, well development and well purging techniques.     

Prediction of Chemical Oxygen Demand (COD) Based on Wavelet Decomposition and Neural Networks

The chemical oxygen demand (COD) parameter of a wastewater treatment plant is predicted based on wavelet decomposition, entropy, and neural networks (NN) for rapid COD analysis. This paper also describes the usage of wavelet and NNs for parameter prediction. Data from a wastewater treatment plant in Malatya, Turkey, were used. This dataset consists of daily values of influents and effluents for a year. To reduce the dimension of input parameters and to decrease the NN training time, wavelet decomposition and entropy were used. Test results were presented graphically. The test results of the trained model were found to be closer to the measured COD values.     

Using Na/K Ratios to Identify the Potential Impacts of Sewage Effluent on Groundwater Quality in Sohag,Egypt

Improper disposal of wastewater is an important source of groundwater contamination, as it poses serious threats to the environment and human health. In this case study, 18 groundwater and 3 sewage effluent samples were collected from the area adjacent to a wastewater treatment plant in Sohag, Egypt. These samples were subjected to detailed chemical and bacteriological analyses to quantify the potential impact of sewage effluent on the groundwater quality using geochemical indicators. The groundwater aquifer in the study area is represented by the highly permeable Qena Sands that are composed of sands and gravels. The bacteriological analyses indicated the presence of fecal coliform in groundwater at wells nearby the wastewater ponds and farm lands. NH₄ concentration of the contaminated groundwater samples ranged from 0.36 to 5.70 mg/L (78% of the samples > 1.20 mg/L) and the NH₄ in the non‐impacted samples ranged from 0.40 to 2.23 mg/L (22% > 1.20 mg/L). Variations in NH₄ concentrations are due to the transformation processes occurring in the aquifer. The groundwater samples were categorized based on the Na/K ratio into two classes. The first class shows the Na/K ratios vary from 2.52 to 12.19 for sewage effluent and contaminated samples, while in the second class they range from 12.85 to 31.60 for non‐impacted samples. As a result, the Na/K ratio in combination with other chemical and microbiological indicators is a useful screening tool for assessing possible sewage influence on shallow groundwater from shallow wells.     

On the Problem of Sample Preservation by Freezing

During routine analysis of running water samples differences of the analytical results of water‐soluble anions were observed between analysis carried out immediately after sampling and after storage of the cooled/frozen sample. This phenomenon was investigated for some years with the “model ion” chloride. A high number of samples (ca. 210) were analysed over three years with different analytical methods, and by alteration of the sample containers the discrete physical influence of the wall effect of the sample vessel could be worked out definitely. No significant differences occur with the mean value of the year but the single values have high differences in the positive or negative direction. Assuming a similar behaviour of other water constituents when preserved by freezing the analytical values had to be looked at very critically.