High Concentrations Of Suspended Solids Research Articles

<b>Chemical coagulants and <i>Moringa oleifera</i> seed extract for treating concrete wastewater

Wastewater from concrete plants has a high pH and a high concentration of suspended solids, necessitating treatment before reuse or discharge into the environment. The objective of this study is to evaluate the efficiency of two chemical coagulants, aluminum sulfate ( Al 2 (SO 4 ) 3 ) and iron chloride ( FeCl 3 ), and a natural coagulant, Moringa oleifera (MO), all in their soluble forms, in the treatment of wastewater from concrete plants. To this end, the efficiencies of the three coagulants, in combinations with different proportions, were tested. The quality parameters of the wastewater obtained after the treatments were compared to the limit values for non-potable water. The use of coagulants in their soluble form potentiates their effect, especially when preparing the MO extract, i.e., greater amounts of the protein responsible for the coagulation is extracted. A mixture with MO and Al 2 (SO 4 ) 3 in a 20:80 proportion showed the best results, with 97.5% of the turbidity removed at 60 min. of sedimentation, allowing the treated water to be used for washing vehicles and flushing toilets. The FeCl 3 treatment produced a high concentration of chlorides, which could cause corrosion problems, and is therefore not recommended for concrete wastewater treatment.

鄱阳湖浮游甲壳动物群落结构特征

PDF HTML阅读 XML下载 导出引用 引用提醒 鄱阳湖浮游甲壳动物群落结构特征 DOI: 10.5846/stxb201505070941 作者: 作者单位: 中国科学院南京地理与湖泊研究所/湖泊与环境国家重点实验室,中国科学院南京地理与湖泊研究所/湖泊与环境国家重点实验室,江西省鄱阳湖水利枢纽建设办公室,江西省鄱阳湖水利枢纽建设办公室,中国科学院南京地理与湖泊研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点基础研究发展计划（973计划）资助项目（2012CB417006）；江西省水利厅委托资助项目 Spatial and temporal distribution characteristics of planktonic crustaceans in Lake Poyang Author: Affiliation: State Key Laboratory of Lake Science and Environment,Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences,State Key Laboratory of Lake Science and Environment,Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences,Bureaux of Poyang Lake Water Conservancy Construction,Bureaux of Poyang Lake Water Conservancy Construction,State Key Laboratory of Lake Science and Environment,Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:鄱阳湖是中国第一大淡水湖，具有“丰水为湖，枯水为河”的独特特点。为探讨鄱阳湖浮游甲壳动物群落结构及其时空分布的特征，于2009年全年采集其不同季节、不同水位期的浮游甲壳动物样品进行定量分析。结果显示，鄱阳湖浮游甲壳动物群落结构总体与河流浮游甲壳群落具有相似性。无节幼体、象鼻溞、剑水蚤等河流优势类群在鄱阳湖浮游甲壳动物中占优势；而哲水蚤和溞属仅在低水位季节占优势，枝角类丰度仅在高温、高水位、流速缓的季节高过桡足类。丰水期浮游甲壳动物平均丰度和生物量远远高于枯水期，可达枯水期的50倍，差异极其显著（P < 0.01）。温度和水位变化引起的环境因子改变是导致鄱阳湖浮游甲壳动物发生季节演替的主要原因；而营养盐对浮游甲壳动物的影响并不显著。空间上浮游甲壳动物群落构成明显不同，年均丰度最高和最低的点均出现在河口地区。因此：对于换水周期短，水交换速率快的水体，应该充分考虑水文条件对生物的影响。 Abstract:Poyang Lake, the largest freshwater lake in China, has a large water surface only during wet seasons. However, for most time of the year, about nine months, Poyang Lake is more like a riverine rather than a lacustrine ecosystem, with short water residence time, rapid flows, high suspended solid concentrations, and low water transparences. Considerable studies have focused on the role of trophic state by defining the spatial and temporal distributions of zooplankton, but few studies have investigated the habitat types according to different hydrological states. The above mentioned riverine characteristics are known to have a negative impact on plankton abundance and are responsible for the low plankton standing crops. In this study, we investigated the community structure and seasonal succession pattern of crustacean zooplankton in Lake Poyang and their correlation to various environmental factors. Our findings suggested that planktonic crustacean community structure in Poyang Lake was remarkably similar to that in a river ecosystem. Nauplii, Bosmina spp., and cyclops that usually dominant riverine habitats were found in Poyang Lake. Nauplii, copepodites, calanoids, cyclops, Bosmina spp., and Daphnia could be found throughout the year. The remaining species (normally thermophilic) could only be observed during certain seasons, for example, Diaphanosoma spp. was only found in summer and autumn. The abundance of cladocerans was higher than that of copepods only in the seasons with high water levels and high water temperature and slow velocity. The average abundance and biomass of planktonic crustaceans varied significantly (P < 0.01) between the high-water-level season and low-water-level season. The crustacean abundance in the wet season was 50 times higher than that during the dry season.Natural lakes, reservoirs, and rivers are three diverse ecological systems according to their hydrologic characteristics. Their water retention time and flow velocity are markedly different from each other. Limnological and hydrological factors were compared among these ecological systems to analyze their influences on the distribution and abundance of planktonic crustaceans. Seasonal succession of crustaceans is mainly controlled by water temperature and environmental factors that are influenced by water level. The densities of most zooplankton species are positively correlated with water temperature and chlorophyll-a concentrations. However, nutrients seemed to have a negative effect on planktonic crustacean assemblage in Poyang Lake, which was similar to that in riverine habitats other than lentic lakes. We found a close relationship between community structure and habitat types, as has been reported by many other studies. Therefore, crustacean abundances in Poyang Lake varied consistently with water temperature and water level, but oppositely with nutrients. Owing to the complex hydrologic and water quality situations, the highest and lowest average abundances of planktonic crustaceans spatially appeared in the estuary zone. Therefore, we suggest that, for rapid water exchanging water bodies, hydrologic factors should be considered adequately. 参考文献 相似文献 引证文献

Combining Landsat TM/ETM+ and HJ-1 A/B CCD Sensors for Monitoring Coastal Water Quality in Hong Kong

High suspended solid (SS) concentrations in coastal waters are aesthetically undesirable, and adversely affect fisheries and coastal ecosystems. Environmental agencies usually require frequent measurements of SS over coastal regions at a spatially detailed level for water quality assessment and control. To develop a method for SS estimation in the complex coastal waters of Hong Kong, an archive of 57 Landsat Thematic Mapper (TM), Enhanced Thematic Mapper Plus (ETM+), and HJ-1 A/B Charged Couple Device (CCD) images over a 13-year period from January 2000 to December 2012 was used. Atmospherically corrected Landsat TM/ETM+ and HJ-1 A/B CCD bands 1-4 along with 240 in situ field samples of SS concentration collected within 2 h of image acquisition, were used to develop and validate regression models over a wide range of SS concentrations from 0.5-56.0 mg/L. The best representation of actual SS concentrations was given by the log-transformed combination of Band 2 (Green, 0.52-0.60 μm) and Band 3 (Red, 0.63-0.69 μm), with correlation coefficient (R) of 0.85, root-mean-square error of 2.60 mg/L and mean absolute error of 2.04 mg/L. This is attributed to the sensitivity of SS to green and red wavelengths specific to the characteristic refractive index and grain size of SS found in Hong Kong waters. This letter is considered more robust than previous studies, due to the much larger number of images and in situ samples used for model development and validation, as well as the different times of year and wide range of SS concentrations investigated.

The effect of the suspended solid concentration on the daytime vertical distribution of Euphausia pacifica in the Yellow Sea, Korea

The Yellow Sea, characterized by a high concentration of suspended solids, is a semi-enclosed, marginal sea and shallow water in the northwestern Pacific Ocean, located between the Korean Peninsula and China. In this paper, we describe the response of acoustically determined weighted mean depth (WMD) of the krill, Euphausia pacifica, to variations in suspended solid concentration (SSC) during the daytime in spring and summer. E. pacifica was identified from the difference in the volume backscattering strength at 38 and 200 kHz. Our results indicated a correlation between the WMD of E. pacifica and the density of SSC during the daytime in both spring and summer. E. pacifica aggregation was distributed mainly near the bottom when the SSC was relatively low, but did not descend to the bottom when the SSC was relatively high. This implies that the SSC may be an important environmental factor affecting the behavior of E. pacifica.

Particulate flow at the mouth of the Soummam watershed (Algeria)

In Algeria, the particulate flow in rivers is poorly quantified in the wadi due to the absence and the non‐standardization of the acquisition of measurement data. Most studies on particulate flows are quantified from time series of hydrometric stations. The present study is based on weekly sampling of water at the mouth of the Soummam watershed for the hydrological year 2011/2012. The sediment flux is analyzed from measurements of suspended solids (SS). The determination coefficients between the annual and seasonal “ liquid flow–solid flow‐” relationships vary from 75% to 82%, respectively. During this period, the watershed of 9125 km2 has provided a solid input estimated to 4.9 × 106 t yr−1, hence a specific flow of 538 t km−2 yr−1. In general, autumn floods were characterized by high concentrations of SS, which varies from 820 to 1275 mg L−1. The most important sediment transport volumes were observed during the period of December to February, this period is characterized by strong turbulence, due to extreme flows, favoring the largest volumes of solid transport. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 204–211, 2016

Effects of Climate Change on the Movement of Turbidity Flow in a Stratified Reservoir

In this study, we investigated the effects of climate change on the movement of the turbidity flow in a stratified reservoir. Reservoir turbidity is primarily caused by the concentration of suspended solids in a watershed. Under the effects of climate change, which increases the frequency and intensity of extreme weather events in the Asian monsoon area, turbidity can be considered to be an essential water quality variable in a reservoir that supplies drinking water. We adopted a two-dimensional hydrodynamic water quality model coupled to a watershed model and used a future climate scenario applied to the Yongdam Reservoir in South Korea. To account for the uncertainty of climate change scenarios and the extent of the variation of both temperature and precipitation, three cases each from the 2050’s and 2090’s were selected for simulation. The simulations predicted that the significance of the summer stratification would produce a vertical circulation lower than 8 m in the warming reservoir of the 2090 scenario in comparison to 15 m in the 2050 scenario. The limited vertical circulation caused the density plume to spread within a depth of 8 m of the reservoir, isolating the upper water with high suspended solid concentrations from the hypolimnetic water. The results of this study provide the optimum horizontal and vertical location of the intake aqueducts to obtain drinking water with low turbidity during extremely heavy rainfall.

Study of OMWWs suspended solids destabilization to improve membrane processes performance

Olive Mill waste waters (OMWWs) are extremely polluting and need to be treated before being discharged or to provide opportunities for their reuse or recycling. Because of their high suspended solids content, a pre-treatment method able to abate the severe fouling occurring during the subsequent micro and ultrafiltration membrane processes is mandatory. In this paper, a new approach to the OMWWs pre-treatment based on suspension destabilization as a function of its zeta potential has been developed. The original feature of this method relies on the precise identification of the suspension destabilization conditions by zeta potential and light scattering measurements. The obtained results indicated that the ideal destabilization conditions occur at pH 1.8 (near to the isoelectric point), corresponding to the lowest zeta potential value and to the formation of large agglomerates with a mean particle size equal to 21μm. The pre-treatment proved to be relevant for achieving the complete elimination of all the suspended solids making the OMWWs more suitable for the following microfiltration (MF) and ultrafiltration (UF) processes.The performance of different membrane materials during MF and UF processes was evaluated in terms of total and dissolved solids, TOC reduction and phenols rejection. The highest permeate fluxes, 60 and 23 L/hm2 were obtained in the MF and UF processes, respectively, using ceramic membranes. Besides, results in terms of phenols quantification indicated that this pre-treatment preserves the polyphenols from oxidation.The suspension destabilization method here described provides a general approach to treat waste water with large suspended solids content, thus it can be easily extended to the pre-treatment of waste waters from different sources with the aim of reducing fouling during MF and UF membrane processes.

Deposition of riverine suspended solids in a shallow bay (Bay of Koper, Gulf of Trieste, northern Adriatic Sea)

Deposition of riverine suspended solids affects operations in ports located in the proximity of river mouths. The Rižana River is the main source of riverine solids in the shallow Bay of Koper (Gulf of Trieste, northern Adriatic Sea). The mean discharge increases rapidly in relation to high precipitation, typical of spring and autumn. During such events, the runoff leads to torrential river flow with high concentration of suspended solids which are consequently deposited in the port zone. Turbidity (NTU) measurements were performed during 2011–2013 in the Rižana and Badasevica Rivers and in the inner part of the bay influenced by fresh water inflow. In parallel, the concentrations of total suspended solids (TSS) and suspended organic matter (SOM) were measured gravimetrically, the latter after combustion, and their grain size distributions were determined using a laser granulometer. The maximum turbidity values in the bay were found in the sea surface layer during the river flood. The linear regression model between TSS and turbidity (NTU) TSS = 1.01 × NTU + 0.91 showed strong positive correlation. The regression analysis between turbidity and SOM also showed strong correlation with a regression equation SOM = 0.12 × NTU + 0.85. The impact of SOM on measurements was hypothesized by the rather poor model fit of the regression analysis between TSS and river discharge, which is mainly related to high SOM variations. The grain size spectra of riverine and nearshore surface TSS in the proximity of the river mouth were skewed and sorted with the mode size mostly around 10 μm. Considering the TSS mass in the sea surface layer, the yearly TSS input into the bay is estimated to be ~18 × 103 t. Using the average TSS concentration in the Rižana River and the average Rižana River discharge, the yearly input would be ~2 × 103 t. The discrepancy between both calculated inputs is probably related to the TSS input during high river discharge which occurs in short periods. A maximum deposition rate of 80 g m2 day−1 is mostly restricted to the second port basin. Less than 50 % of the introduced TSS settles within the second port basin during mean river flow conditions. The regression model was found to be a useful tool to estimate TSS and SOM concentrations from turbidity data in rivers and the coastal sea, thus providing an evaluation of riverine TSS and SOM input and deposition into the small bay, which in turn affects local port activities.

A compact on-site UASB–EGSB system for organic and suspended solid digestion and biogas recovery from department store wastewater

This research aims to develop a compact on-site anaerobic treatment of department store wastewater and biogas recovery by a two-step UASB–EGSB (Upflow Anaerobic Sludge Blanket – Expanded Granular Sludge Blanket) as an energy-saving system. The wastewater came from a department store in Bangkok city having COD in the range of 450–700 mg/L and high suspended solids content in the range of 230–300 mg/L. The applied organic loading rate to the pilot-scale UASB–EGSB system was designed at 5 kg COD/m3-day. The upflow velocity of EGSB reactor was varied to 4, 6, 8 m/hr. The results of the pre-treatment with the UASB reactor show that the UASB reactor is efficient to remove suspended solids and COD in raw wastewater, viz.77.4 and 65.9%, respectively. This means that the UASB reactor plays an important role to entrap and digest main part of suspended solids from raw wastewater prior to the EGSB reactor. The overall efficiencies of UASB–EGSB system for removal COD, BOD and SS were 90.5, 90.7 and 92.2%, respectively. Moreover, an increase in upflow velocity of EGSB reactor could slightly increase COD and BOD removal efficiencies; however, did slightly decrease in SS removal efficiency. Furthermore, specific methanogenic activity (SMA) of the granular sludge inside the EGSB reactor was found in the range of 0.06–0.09 gCOD-CH4/gVSS-day.

Effects of aeration on/off times and hydraulic retention times in an intermittently aerated membrane bioreactor

Intermittently aerated membrane bioreactor is a process that combines an intermittently aerated bioreactor with a membrane. A membrane bioreactor can achieve complete separation between solids and liquids, and improve nitrogen removal because the reactor contains bacteria relevant to nitrifying and denitrifying. This paper is an investigation into removal efficiencies on two operation factors (aeration on/off times and hydraulic retention times (HRTs)). Permeate concentrations of T-N and T-P in 60 min-on/60 min-off were 19.6 and 4.41 mg/L, respectively, and permeate concentrations of T-N and T-P in 30 min-on/30 min-off were 22.7 and 4.56 mg/L, respectively. Accordingly, we found that 60 min-on/60 min-off was superior to 30 min-on/30 min-off. This was due to the high mixed liquid suspended solid concentration and the sufficient aerobic/anoxic time for the reaction. In the experiments with HRTs of 6, 9, and 12 h, the removal efficiency of organic matter was above 90% under all conditions. However, the HRT of 6 h was the best condition for removal efficiencies of T-N and T-P, due to high chemical oxygen demand loading rates per unit time of the influent.

Development and testing of a fully gravitational submerged anaerobic membrane bioreactor for wastewater treatment

A gravity-operated submerged anaerobic membrane bioreactor (SAnMBR) was set up in order to test its principle of operation as an alternative to conventional pumped permeation of the membrane. This operating mode allowed the membrane flux rate to be measured accurately whilst maintaining a constant transmembrane pressure (TMP), and allowed small transient variations in the flux rate to be observed. The reactor was operated at 36°C for a period of 115 days using a nutrient-balanced synthetic substrate with a high suspended solids concentration. Membrane cleaning was in situ by a gas scouring system using recirculation of headspace biogas. With an initial TMP of 7.0 kPa, the membrane flux slowly decreased due to membrane fouling and had not reached a constant value by day 71. The results indicated that the system was still acclimatizing up to 50 days after start-up; but from that point onwards, performance parameters became much more stable. A constant flux of 2.2 L m−2 h−1 was achieved over the last 45 days after the TMP was reduced to 2.3 kPa. The stable flux was maintained over this period and the loading raised to 1 g COD L−1 d−1 by increasing the influent strength. Under these conditions, the average chemical oxygen demand removal efficiency was 96% and the specific methane potential was 0.31 L CH4 g−1 COD removed.

Sorption and biodegradation of selected benzotriazoles and hydroxybenzothiazole in activated sludge and estimation of their fate during wastewater treatment

Biodegradation of benzotriazole (BTR), 5-chlorobenzotriazole (CBTR), xylytriazole (XTR), 4-methyl-1H-benzotriazole (4TTR), 5-methy-1H-lbenzotriazole (5TTR) and 2-hydroxybenzothiazole (OHBTH) was studied in activated sludge batch experiments under aerobic and anoxic conditions, presence of organic substrate and different sludge residence times (SRTs). Their sludge-water distribution coefficients were also calculated in sorption experiments and ranged between 87 and 220Lkg−1. Significant biodegradation of BTR, CBTR, XTR and OHBTH was observed in all biotic experiments. Half-life values ranged between 23 and 45h (BTR), 18 and 47h (CBTR), 14 and 26h (XTR), 6.5 and 24h (OHBTH). The addition of substrate did not suppress biodegradation kinetics; whereas in some cases accelerated biodegradation of microcontaminants. Except for CBTR, no effect of SRT on biodegradation constants was observed. Prediction of micropollutants removal in Sewage Treatment Plants (STPs) indicated that they will be partially removed, mainly due to aerobic biodegradation. Higher removal is expected at STPs operating at higher SRT and higher suspended solids concentrations.

Treatment of papermaking tobacco sheet wastewater by electrocoagulation combined with electrochemical oxidation.

Attempts were made in this study to examine the efficiency of electrocoagulation (EC) using aluminum (Al) anode and stainless steel net cathode combined with electrochemical oxidation with a β-PbO₂anode or a mixed metal oxide (MMO) anode for treatment of papermaking tobacco sheet wastewater, which has the characteristics of high content of suspended solids (SS), intensive color, and low biodegradability. The wastewater was first subjected to the EC process under 40 mA/cm² of current density, 2.5 g/L of NaCl, and maintaining the original pH of wastewater. After 6 minutes of EC process, the effluent was further treated by electrochemical oxidation. The results revealed that the removal of SS during the EC process was very beneficial to mass transfer of organics during electrochemical oxidation. After the combined process, 83.9% and 82.8% of chemical oxygen demand (COD) removal could be achieved on the β-PbO₂and MMO anodes, respectively. The main components of the final effluent were biodegradable organic acids, such as acetic acid, propionic acid, butyric acid, valeric acid, and hexahyl carbonic acid; the 5-day biochemical oxygen demand/chemical oxygen demand (BOD₅/COD) ratio increased from 0.06 to 0.85 (Al + β-PbO₂) or 0.80 (Al + MMO). Therefore, this integrated process is a promising alternative for pretreatment of papermaking tobacco sheet wastewater prior to biological treatment.

Analysis of the Production and Treatment of Wastewater in the Southeast of Coahuila, Mexico

Analysis of the Production and Treatment of Wastewater in the Southeast of Coahuila, Mexico Elsa Nadia Aguilera González, Alfredo Valdés Ramos, Gloria Tobón Echeverri, Salvador Carlos Hernández, Luis Samaniego Moreno, Manuel Antonio Álvarez Garza, Lourdes Díaz Jiménez Abstract This paper deals with the study of wastewater production, municipal treatment plants performance, and utilization of treated wastewater in the southeast of Coahuila, Mexico. The objective is to identify the status of wastewater in order to propose alternatives to increase the use of treated wastewater. Influent and effluent on three municipal wastewater treatment plants were analyzed considering four parameters. Results show that the wastewater presents a high concentration of total suspended solids; nevertheless the effluents meet the current environmental standards. Then the treated wastewater requires additional treatment before to be applied in industrial processes, but it can be used for irrigation purposes. Full Text: PDF DOI: 10.15640/jaes.v4n1a20

Effective Pharmaceutical Wastewater Degradation via SCWO with Ethylene Glycol

Pharmaceutical wastewaters are generated through complex manufacturing processes that contain a variety of organic and inorganic constituents, and are usually characterized by a high concentration of chemical oxygen demand (COD), suspended solids, dissolved solids (salts), toxicity, and refractory compounds. Therefore, it must be treated. The treatment of a pharmaceutical wastewater (PWW) using the supercritical water oxidation (SCWO) method was investigated to improve the degradation of the complex-mixture of organic compounds present in the wastewater. The effects of H2O2 dosage, reaction time, temperature, initial COD, and concentration of ethylene glycol on COD removal were studied with laboratory bench-scale experiments. The results indicated that the removal process was more effective under experimental conditions. Adding ethylene glycol accelerates the destruction of pharmaceutical wastewater. The best COD removal of pharmaceutical wastewater reached 97.8%. This investigation will provide a fundamental method for developing a pretreatment method of industrial pharmaceutical wastewater with flexibility, simplicity and high activity.

Optimization of Process Parameters for Pharmaceutical Wastewater Treatment

Pharmaceutical wastewaters are generated through complex manufacturing processes that contain a variety of organic and inorganic constituents, and are usually characterized by a high concentration of chemical oxygen demand (COD), suspended solids, dissolved solids (salts), toxicity, and refractory compounds. In this paper, wet peroxide oxidation (WPO) was adopted to treat pharmaceutical wastewater. Central composite design, an experimental design for response surface methodology (RSM), was used to create a set of 30 experimental runs needed for optimizing operating conditions. The experimental results show that WPO could effectively reduce COD by 97.5% at optimum conditions: temperature is 260oC, H2O2 excess (HE) is 0, the initial concentration of pharmaceutical wastewater is 45,000 mg/L, and reaction time is 10 min. WPO process is possibly suitable for a primary treatment for pharmaceutical wastewater. Response surface methodology (RSM) could be effectively adopted to optimize the operating multifactors in a complex WPO process.

Response of reef corals on a fringing reef flat to elevated suspended-sediment concentrations: Moloka'i, Hawai'i.

A long-term (10 month exposure) experiment on effects of suspended sediment on the mortality, growth, and recruitment of the reef corals Montipora capitata and Porites compressa was conducted on the shallow reef flat off south Molokaʻi, Hawaiʻi. Corals were grown on wire platforms with attached coral recruitment tiles along a suspended solid concentration (SSC) gradient that ranged from 37 mg l−1 (inshore) to 3 mg l−1 (offshore). Natural coral reef development on the reef flat is limited to areas with SSCs less than 10 mg l−1 as previously suggested in the scientific literature. However, the experimental corals held at much higher levels of turbidity showed surprisingly good survivorship and growth. High SSCs encountered on the reef flat reduced coral recruitment by one to three orders of magnitude compared to other sites throughout Hawaiʻi. There was a significant correlation between the biomass of macroalgae attached to the wire growth platforms at the end of the experiment and percentage of the corals showing mortality. We conclude that lack of suitable hard substrate, macroalgal competition, and blockage of recruitment on available substratum are major factors accounting for the low natural coral coverage in areas of high turbidity. The direct impact of high turbidity on growth and mortality is of lesser importance.

Characterization and treatment of flour mills wastewater for reuse – a case study of Al-kausar Flour Mills, Pakistan

Pakistan is increasingly confronted with shortage of fresh water resources, as annual per capita water availability has reduced to less than 1,000 m3. Wastewater reclamation and reuse practices must be adopted to deal with the situation. For this purpose, small and medium scale industries can play a vital role. With this mind set, wastewater from Al-Kausar Flour Mills Islamabad (AFM), Pakistan was investigated using physico-chemical treatment options. Total water consumption of AFM is 74.1 m3/d, and groundwater is being pumped for 8 h/d. Four experimental trains were tested using various combinations of pre-sedimentation, horizontal roughing filter, coagulation/flocculation/settling setup, and multimedia filtration. Ferric chloride and alum were used as coagulants. Results revealed that flour mill wastewater had high concentration of total suspended solids. Ferric chloride provided appreciable suspended solids removal in terms of turbidity. While, every option tested, removed over 98% of turbidity but option C, with 25 mg/L ferric chloride dosage, produced effluent fit for water reuse in the industry. It was also evaluated that AFM could save up to PKR 83,500.0 (US $800) in terms of energy cost and ground water volume of at least 1.6 ML per year.

Trace metals in estuaries in the Russian Far East and China: Case studies from the Amur River and the Changjiang

This paper compares the distributions of dissolved and particulate forms of Mn, Fe, Ni, Cu, Zn, Cd, and Pb in the estuaries of the largest rivers in East Asia: the Amur River and the Changjiang (Yangtze River). High suspended solid concentrations, elevated pH, and relatively low dissolved trace metal concentrations are characteristics of the Changjiang. Elevated dissolved Fe and Mn concentrations, neutral pH, and relatively low suspended solid concentrations are characteristics of the Amur River. The transfer of dissolved Fe to suspended forms is typical in the Amur River estuary, though Cd and Mn tend to mobilize to solution, and Cu and Ni are diluted in the estuarine system. Metal concentrations in suspended matter in the Amur River estuary are controlled by the ratio of terrigenous riverine material, enriched in Al and Fe, and marine biogenic particles, enriched in Cu, Mn, Cd, and in some cases Ni. The increase in dissolved forms of Mn, Fe, Ni, Cu, Cd, and Pb compared with river end-member is unique to the Changjiang estuary. Particle–solution interactions are not reflected in bulk suspended-solid metal concentrations in the Changjiang estuary due to the dominance of particulate forms of these metals. Cd is an exception in the Changjiang estuary, where the increase in dissolved Cd is of comparable magnitude to the decrease in particulate Cd. Despite runoff in the Amur River being lower than that in the Changjiang, the fluxes of dissolved Mn, Zn and Fe in the Amur River exceed those in the Changjiang. Dissolved Ni, and Cd fluxes are near equal in both estuaries, but dissolved Cu is lower in the Amur River estuary. The hydrological and physico-chemical river characteristics are dominated at the assessment of river influence on the adjoining coastal sea areas despite differences in estuarine processes.

Distribuição de massa molar em um biorreator com membrana para tratamento de efluente de laticínios

Os biorreatores com membrana (BRM) apresentam-se como um dos processos mais promissores para tratamento de águas residuárias com elevada carga orgânica, como os efluentes de laticínios, propiciando a geração de um efluente com elevada qualidade e adequado ao reuso direto ou após tratamento terciário. O objetivo desse trabalho foi avaliar o uso de BRM para tratamento de efluente de indústria de laticínios e utilizar a distribuição de massa molar da alimentação, do permeado e da fração solúvel do lodo como ferramenta para a investigação dos mecanismos de remoção dos poluentes no sistema. O BRM se mostrou um sistema viável para o tratamento do efluente em questão, apresentando eficiências de remoção de demanda química de oxigênio (DQO) e cor aparente de 98 e 99%, respectivamente. Através da distribuição de massa molar foi possível observar a alta capacidade de biodegradação e a estabilidade proporcionada pelo BRM, já que, mesmo em situações de alterações constantes nas características da alimentação, o líquido reacional sempre apresentou baixas concentrações de poluentes. Ressalta-se também a importância da membrana no sistema, uma vez que, além de permitir a retenção completa de biomassa e a operação com idades de lodo e concentração de sólidos suspensos maiores, pode proporcionar ainda a retenção de compostos que não foram biodegradados, contribuindo para a geração de um efluente tratado com alta qualidade.