Test of membrane bioreactor for waste water treatment of a petrochemical complex

Membrane bioreactor (MBR) used in water and waste water treatment is a developing technique for water pollution control and water reuse. This paper described a membrane bioreactor for treatment of waste water in a petrochemical complex. The experimental MBR was a lab scale one composed of an activated sludge bioreactor unit and an ultrafiltration membrane unit. The relationship of COD removal with MLSS and HRT in this MBR was studied. The effects of crossflow velocity, backwash interval and volume of flush liquid on the flux were discussed. The results showed that average removal of COD, oil, SS and turbidity in petrochemical waste water by the MBR was 91%, 86%, 92% and 99%, respectively. The average removal of NH 3 N and total phosphorous was 85% and 82% respectively. A coefficient of COD removal, k , was 0017—0080 L/(mg.d). The membrane flux maintained higher than 60 L/hm 2 bar for 34 days without chemical cleaning when the velocity of crossflow was 35—39 m/s and the backwash interval was 30 minutes and backwash duration at 20 seconds. The results indicated that it is feasible for MBR technology to be used in petrochemical waste water treatment. The treated water could be considered as a source of to make up water for industrial cooling system or to be reused for other purposes.

Design and Sizing of an Ecological Wastewater Treatment System in a School Environment: A Case Study of Ndiebene Gandiol 1 School

The primary objective of this study was to design and size a sustainable sanitation solution for the Ndiebene Gandiol 1 school located in the eponymous commune in northern Senegal. Field investigations led to the collection of wastewater samples. Their analysis revealed specific pollutant loads, including loads of BOD5 3.6966 kgO2/day and COD of 12.8775 kgO2/day, which were central to the design phase. Following a rigorous assessment of the existing sanitation infrastructure, constructed wetland (CWs) emerged as the most appropriate ecological solution. This system, valued for its ability to effectively remove contaminants, was tailored to the specific needs of the site. Consequently, the final design of the filter extends over 217.16 m2, divided into two cells of 108.58 m2 each, with dimensions of 12.77 m in length and 8.5 m in width. The depth of the filtering medium is approximately 0.60 m, meeting the standards while ensuring maximized purification. Typha, an indigenous and prolific plant known for its purification abilities, was selected as the filtering agent. Concurrently, non-crushed gravel was chosen for its proven filtration capacity. This study is the result of a combination of scientific rigor and design expertise. It provides a holistic view of sanitation for Ndiebene Gandiol. The technical specifications and dimensions of the constructed wetland filter embody an approach that marries indepth analysis and practical application, all aimed at delivering an effective and long-lasting solution to the local sanitation challenges. By integrating precise scientific data with sanitation design expertise, this study delivers a holistic solution for Ndiebene Gandiol. The detailed dimensions and specifications of the constructed wetland filter reflect a methodology that combines meticulous analysis with practical adaptation, aiming to provide an effective and sustainable response to the challenges of rural and school sanitation in the northern region of Senegal.

Application of Plant-Based Coagulants and Their Mechanisms in Water Treatment:A Review

This review describes the mechanisms of natural coagulants.It provides a good understanding of the two key processes of coagulation-flocculation:adsorption and charge neutralization,as well as adsorption and bridging.Various factors have influence the coagulation/flocculation process,including the effect of pH,coagulant dosage,coagulant type,temperature,initial turbidity,coagulation speed,flocculation speed,coagulation and flocculation time,settling time,colloidal particles,zeta potential,the effects of humic acids,and extraction density are explained.The bio-coagulants derived from plants are outlined.The impact of organic coagulants on water quality,focusing on their effects on the physicochemical parameters of water,heavy metals removal,and bacteriological water quality,is examined.The methods of extraction and purification of plant-based coagulants,highlighting techniques such as solvent extraction and ultrasonic extraction,are discussed.It also examines the parameters that influence these processes.The methods and principles of purification of coagulating agents,including dialysis,freeze-drying,ion exchange,electrophoresis,filtration,and centrifugation,are listed.Finally,it evaluates the sustainability of natural coagulants,focusing on the environmental,technical,and economic aspects of their use.At the end of this review,the readers should have a comprehensive understanding of the mechanisms,selection,extraction,purification,and sustainability of plant-based natural coagulants in water treatment.

Ordered mesoporous materials for water pollution treatment:Adsorption and catalysis

To meet the growing emission of water contaminants,the development of new materials that enhance the efficiency of the water treatment system is urgent.Ordered mesoporous materials provide opportunities in environmental processing applications due to their exceptionally high surface areas,large pore sizes,and enough pore volumes.These properties might enhance the performance of materials concerning adsorption/catalysis capability,durability,and stability.In this review,we enumerate the ordered mesoporous materials as adsorbents/catalysts and their modifications in water pollution treatment from the past decade,including heavy metals(Hg^(2+),Pb^(2+),Cd^(2+),Cr^(6+),etc.),toxic anions(nitrate,phosphate,fluoride,etc.),and organic contaminants(organic dyes,antibiotics,etc.).These contributions demonstrate a deep understanding of the synergistic effect between the incorporated framework and homogeneous active centers.Besides,the challenges and perspectives of the future developments of ordered mesoporous materials in wastewater treatment are proposed.This work provides a theoretical basis and complete summary for the application of ordered mesoporous materials in the removal of contaminants from aqueous solutions.

A Comparative Analysis of Vetiver and Typha in Ecological Wastewater Treatment Using a Horizontal Flow Constructed Wetlands in Rural Setting

This study presents an assessment of wastewater ecological treatment processes utilizing a horizontal flow bio-reactor at the Ndiebene Gandiol 1 school. It primarily aims to juxtapose the filtration efficacy of two distinct vegetative cells, Vetiver and Typha, in the pursuit of sustainable wastewater management strategies for rural scholastic institutions. A synergistic approach was employed, integrating on-site surveys for site-specific insights and laboratory analyses to quantify the pollutant loads pre- and post-treatment. Our findings indicate that both Vetiver and Typha-infused filter beds significantly reduce most contaminants, with particular success in diminishing chemical oxygen demand (COD) and biological oxygen demand (BOD5). Vetiver was notable for its superior reduction of COD, achieving an average effluent concentration of 74 mg/L, in contrast to Typha’s 155 mg/L. Conversely, Typha excelled in suspended solids removal, registering 1 mg/L against Vetiver’s 3 mg/L. While both systems notably surpassed the target metrics across several indicators, including fecal coliform reduction, our results pinpoint the need for refinement in phosphate remediation. Conclusively, the study underscores the efficacy of both Vetiver and Typha systems in rural wastewater treatment contexts, with their integrative application potentially paving the way for enhanced system robustness and efficiency. The outcomes herein highlight the imperative for continued research to further hone these ecological treatment modalities, especially concerning phosphate elimination.

STUDY AND SIMULATION OF AN ACTIVATED SLUDGE TREATMENT FOR METHYL VIOLET WASTE WATER

This paper researched a promising biological treatment of methyl violet waste water by methods of activated sludge.Effects of temperature and pH were studied on this process.Kinetic equation of the substrate biodegradation was investigated in the experimental range.It was studied and simulated that flow within the bubble region of this bioreactor according to the κ ε two fluid equation.Simulation results agree well with experimental data.

THE INVESTIGATION ON PHOTOCATALYTIC TREATMENT OF WASTE WATER CONTAINING PHENOL OVER ZnO

This paper adopts a medium pressure mercury lamp as light source and ZnO powder as catalyst to investigate the effect of radioactive wave length, component of phenol ZnO suspension and stirring method on phenol decomposition rate. The optimized conditions for the phenol decomposition are: (1) Radioactive wave length: 360～420 nm; (2)Phenol concentration in the suspension is less than 200 mg/l; (3)ZnO concentration is 3～8 g/l; (4)pH value is 5～7; (5)Reaction temperature is 25℃～40℃; (6)Agitation at atmosphere. Phenol can decompose in two ways: (1)Reacting with photogenerated cavity; (2)Reacting with ·OH radical.

Research of Oxidation Resistance of PVDF Hollow Fiber Membrane Used in Water Treatment

[Objective] The aim was to research the influences of different formulations on oxidation resistance of PVDF hollow fiber membrane.[Method]The immersion precipitation phase inversion method was employed to make casting solution with different formulations into hollow fiber membrane.The membrane was immersed in 1% NaClO solution for testing its performance changes.[Result]The membrane made by materials with bigger molecular weight had better oxidation resistance performance;the surfactant tween-80 could increase water flux,but lead to lower rupture intension;Pore-forming agent PEG400 do better than PVP in the oxidation resistance of membrane.[Conclusion]This study will provide a good idea for the development of the PVDF membrane with high oxidation resistance.

Treatment Efficiencies of Constructed Wetlands for Eutrophic Landscape River Water

The efficiencies of two types of constructed wetlands for the treatment of low-concentration polluted eutrophic land- scape river water were studied in the western section of the Qingyuan River at the Minhang campus of Shanghai Jiaotong University.The first wetland was a single-stage system using gravel as a filtration medium,and the second was a three- stage system filled with combinations of gravel,zeolite,and fly ash.Results from parallel operations of the wetlands showed that the three-stage constructed wetland could remove organics,nitrogen, and phosphorus successfully.At the same time,it could also decrease ammoniacal odour in the effluent.Compared to the single-stage constructed wetland,it had better nutrient removal efficiencies with a higher removal of 19.37%-65.27% for total phosphorus (TP) and 21.56%- 62.94% for total nitrogen (TN),respectively,during the operation period of 14 weeks.In terms of removal of chemical oxygen demand (COD), turbidity,and blue-green algae,these two wetland systems had equivalent performances.It was also found that in the western section of the test river,in which the two constructed wetlands were located, the water quality was much better than that in the eastern and middle sections without constructed wetland because COD,TN, and TP were all in a relatively lower level and the eutrophication could be prevented completely in the western section.

Influences of water treatment agents on oil-water interfacial properties of oilfield produced water

The emulsion stability of oilfield produced water is related to the oil-water interfacial film strength and the zeta potential of the oil droplets. We investigated the effects of water treatment agents （corrosion inhibitor SL-2, scale inhibitor HEDP, germicide 1227, and flocculant polyaluminium chloride PAC） on the stability of oilfield produced water. The influence of these treatment agents on oil-water interfacial properties and the mechanism of these agents acting on the oilfield produced water were studied by measuring the interfacial shear viscosity, interfacial tension and zeta electric potential. The results indicated that the scale inhibitor HEDP could increase the oil-water interfacial film strength, and it could also increase the absolute value of the zeta potential of oil droplets. HEDP played an important role in the stability of the emulsion. Polyaluminum chloride （PAC） reduced the stability of the emulsion by considerably decreasing the absolute value of the zeta potential of oil droplets. Corrosion inhibitor SL-2 and germicide 1227 could decrease the oil-water interfacial tension, whereas they had little influence on oil-water interfacial shear viscosity and oil-water interfacial electricity properties.

Particle properties in granular activated carbon filter during drinking water treatment

The elemental composition and bacteria attached in particles were investigated during granular activated carbon （GAC） filtration.The experimental results showed that trapped influent particles could form new,larger particles on GAC surface.The sloughing of individuals off GAC surface caused an increase in effluent particles in the size range from 5 to 25 μm.The selectivity for element removal in GAC filters caused an increasing proportion of metallic elements in the effluent particles.The distribution of molar ratio indicated a complicated composition for large particles,involving organic and inorganic substances.The organic proportion accounted for 40% of total carbon attached to the particles.Compared with dissolved carbon,there was potential for the formation of trihalomethanes by organic carbon attached to particles,especially for those with size larger than 10 μm.The pure carbon energy spectrum was found only in the GAC effluent and the size distribution of carbon fines was mainly above 10 μm.The larger carbon fines provided more space for bacterial colonization and stronger protection for attached bacteria against disinfection.The residual attached bacteria after chorine disinfection was increased to 10 2-10 3 CFU/mL within 24 hours at 25°C.

Particle size distribution and property of bacteria attached to carbon fines in drinking water treatment

The quantitative change and size distribution of particles in the effluents from a sand filter and a granular activated carbon （GAC） filter in a drinking water treatment plant were investigated. The average total concentration of particles in the sand filter effluent during a filter cycle was 148 particles/mL, 27 of which were larger than 2 μm in size. The concentration in the GAC effluent （561 particles/mL） was significantly greater than that in the sand filter effluent. The concentration of particles larger than 2 μm in the GAC filter effluent reached 201 particles/mL, with the amount of particles with sizes between 2 μm and 15 μm increasing. The most probable number （MPN） of carbon fines reached 43 unit/L after six hours and fines between 0.45 μm and 8.0 μm accounted for more than 50%. The total concentration of outflowing bacteria in the GAC filter effluent, 350 CFU （colony-forming units） /mL, was greater than that in the sand filter effluent, 210 CFU/mL. The desorbed bacteria concentration reached an average of 310 CFU/mg fines. The disinfection efficiency of desorbed bacteria was lower than 40% with 1.5 mg/L of chlorine. The disinfection effect showed that the inactivation rate with 2.0 mg/L of chloramine （90%） was higher than that with chlorine （70%）. Experimental results indicated that the high particle concentration in raw water and sedimentation effluent led to high levels of outflowing particles in the sand filter effluent. The activated carbon fines in the effluent accounted for a small proportion of the total particle amount, but the existing bacteria attached to carbon fines may influence the drinking water safety. The disinfection efficiency of desorbed bacteria was lower than that of free bacteria with chlorine, and the disinfection effect on bacteria attached to carbon fines with chloramine was better than that with only chlorine.

Study on coagulation property of metal-polysilicate coagulants in low turbidity water treatment

In order to remove the low turbidity present in surface water, a novel metal-polysilicate coagulant was used to treat the raw water taken from Tanjiang River in Guangdong Province. This study on the effects of Al/Fe molar ratio on the performance of a complex compound formed by polysilicic acid, aluminium and ferric salt (PAFS) showed that PAFS with Al/Fe ratio of 10:3 seemed to have the best coagulation performance in removing turbidity and color. Experimental results showed that under the conditions of polymerization time of 15 d, sedimentation time of 12 min, and pH of 6?8, PAFS with Al/Fe molar ratio of 10:3 had the best coagulation efficiency and lowest residual Al concentration. The turbid- ity decreased from 23.8 NTU to 3.23 NTU and the residual Al concentration was only 0.165 mg/L in the product water. It could be speculated that colloidal impurities and particulate Al were removed by adsorption bridging and electrical neu- tralization of long chain inorganic polymer coagulants.

Application of an expert system using neural network to control the coagulant dosing in water treatment plant

The coagulation process is one of the most important stages in water treatment plant, which involves many complex physical and chemical phenomena. Moreover, coagulant dosing rate is non-linearly correlated to raw water characteristics such as turbidity, conductivity, PH, temperature, etc. As such, coagulation reaction is hard or even impossible to control satisfactorily by conventional methods. Based on neural network and rule models, an expert system for determining the optimum chemical dosage rate is developed and used in a water treatment work, and the results of actual runs show that in the condition of satisfying the demand of drinking water quality, the usage of coagulant is lowered.

Catalytic Effect of Activated Carbon and Activated Carbon Fiber in Non-Equilibrium Plasma-Based Water Treatment

Catalysis and regeneration efficiency of granular activated carbon （GAC） and activated carbon fiber （ACF） were investigated in a non-equilibrium plasma water treatment reactor with a combination of pulsed streamer discharge and GAC or ACF. The experimental results show that the degradation efficiency of methyl orange （MO） by the combined treatment can increase 22% （for GAC） and 24% （for ACF） respectively compared to pulsed discharge treatment alone, indicating that the combined treatment has a synergetic effect. The MO degradation efficiency by the combined treatment with pulsed discharge and saturated GAC or ACF can increase 12% and 17% respectively compared to pulsed discharge treatment alone. Both GAC and ACF show catalysis and the catalysis of ACF is prominent. Meanwhile, the regeneration of GAC and ACF are realized in this process. When H202 is introduced into the system, the utilization efficiency of ozone and ultraviolet light is improved and the regeneration efficiency of GAC and ACF is also increased.

Combination of chlorine and magnetic ion exchange resin for drinking water treatment of algae

The effectiveness of a magnetic ion exchange resin （MIEX） for the treatment of Hongze Lake water in China was evaluated, The kinetics of natural organic matter （NOM） removal at various MIEX doses and contact time, multiple-loading experiments, impacts of MIEX prior to coagulation on coagulant demands and the effectiveness of combination of MIEX, pre-chlorination and coagulation were investigated. Kinetic experimental results show that more than 80% UV254 and 67% dissolved organic carbon （DOC） from raw water can be removed by the use of MIEX alone. 94% sulfate, 69% nitrate and 98% bromide removals are obtained after the first use of MIEX in multiple-loading experiments. It is suggested that MIEX can be loaded up to 1 250 bed volume （BV, volume ratio of tested water to resin） or more without saturation when regarding organics removal as a target. MIEX can remove organics to a greater extend than coagulation and lower the coagulant demand when combining with coagulation. Chlorination experimental results show that MIEX can remove 57% chlorine demand and 77% trihalomethane formation potential （THMFP） for raw water. Pre-chlorination followed by MIEX and coagulation can give additional organic and THMFP removals. The results suggest that MIEX provides a new method to solve thc problem algae reproduction.

Removal of cyclops in pre-oxidizing cooperation water treatment process

Zooplankton cyclops propagates profusely in waterbody, cannot be effectively inactivated by conventional disinfection process, and becomes a troublesome drinking water treatment problem. In this work, the qualitative and quantitative experimental studies were carried out on inactivation of zooplankton cyclops using oxidants, such as chlorine （Cl2）, chlorine dioxide （ClO2）, ozone （O3）, hydrogen peroxide （H2O2）, ozone/hydrogen peroxide （O3/H2O2）, chloramines （Cl2-NH3） and potassium permanganate （KM4nO4）. The influences of various factors include different oxidant dosages, organic substance contents and pH values. The results showed that currently available oxidants used all might inactivate cyclops in some extent. According to the experimental results, chlorine dioxide, ozone, ozone/hydrogen peroxide and chloramines can be selected as effective oxidants for inactivating cyclops because of their strong inactivation abilities. Then the synergic removal effects on cyclops with ozone, ozone/hydrogen peroxide pre-oxidation followed by conventional water treatment processes were investigated, The results showed that ozone and ozone/hydrogen peroxide pre-oxidation can inactivate cyclops effectively, which then can be removed thoroughly by conventional water treatment processes. Cyclops cannot appear in water after filtration with 1.65 mg/L of ozone and 6 mg/L of hydrogen peroxide, with the inactivation rate being 62% before conventional water treatment processes. Cyclops cannot appear in water after filtration with 1.8 mg/L of ozone, with the inactivation rate being 50% before conventional water treatment processes. For different oxidants, when removal rate was the best, the inactivation rate was not the same. These results may provide reference and model for actual waterworks.

Particle monitoring techniques for water treatment applications

A simple optical technique based on fluctuations in light transmitted through flowing suspensions has proved useful in two distinct water treatment applications. The first of these is the monitoring and control of coagulation/flocculation processes, where information on optimum coagulant dosages as well as on the dynamics of floc formation can be derived. The method is suitable for a very wide range of particle concentrations, up to levels found in highly turbid river waters. The second application is as a very sensitive monitor of particles in filtered water. Such monitoring can help to ensure the effective removal of pathogens such as Cryptosporidium from drinking water. Brief accounts of these techniques are given, together with some examples of their use.

Immobilization biological activated carbon used in advanced drinking water treatment

Bacteria separated from a mature filter bed of groundwater treatment plants were incubated in a culture media containing iron and manganese. A consortium of 5 strains of bacteria removing iron and manganese were obtained by repeated enrichment culturing. It was shown from the experiments of effect factors that ironmanganese removal bacteria in the euhure media containing both Fe and Mn grew better than in that containing only Fe, however, they were unable to grow in the culture media containing only Mn. When comparing the bacteria biomass in the case ofp （DO） ：2.8 mg/L andp （DO） ：9. 0 mg/L, no significant difference was found. The engineering bacteria removing the organic and the bacteria removing iron and manganese were simuhaneously inoculated into activated carbon reactor to treat the effluent of distribution network. The experimental results showed that by using IBAC （ Immobilization Biological Activated Carbon） treatment, the removal efficiency of iron, manganese and permanganate index was more than 98% , 96% and 55% , respectively. After the influent with turbidity of 1.5 NTU, color of 25 degree and oflbnsive odor was treated, the turbidity and color of effluence were less than 0.5 NTU and 15 degree, respectively, and it was odorless. It is determined that the cooperation function of engineering bacteria and activated carbon achieved advanced drinking water treatment.

Effect of typhoon with extreme precipitation on mountain reservoir drinking water treatment: a case study in Ningbo, China

Due to frequent drinking water pollution accidents in the past decade, it is common that mountain reservoirs were used as the source of drinking water in China. However, some coastal areas frequently suffer from typhoon with extreme precipitation, which results in the water quality deterioration of the reservoirs. The influence of typhoons with extreme precipitation on Jiaokou reservoir and the emergency treatment process of Maojiaping water treatment plant in the past three typical typhoons with extreme precipitation from the year of 2012-2015 were studied. It was found that the degradation of water quality, such as the increase of turbidity and bacteria index, may not merely appear during the events, but last for several days. Changing the dosage of water purification agent, such as coagulant and disinfectant at right time and place may be an efficient emergency water treatment process. Based on the analysis of water quality variation rule during and after the events, it was also found that emergency treatment can be fully prepared before the arrival of a typhoon with extreme precipitation. And in order to better respond to the typhoon with extreme precipitation, several suggestions are also proposed in this paper as follows: establishing vegetated buffers at right place, such as macrophanerophytes,shrub or herbage, increasing investments in infrastructure management, merging or cancelling the small-scale water treatment plants, preparing adequate water purification agent before the typhoon comes, etc.