Purification Of Effluents Research Articles

Sorption properties of wool

Strict ecological legislation, especially in highly developed countries, imposed requirements for the purification of industrial effluents and the need for efficient oil clean up after sea and inland water spills. Although numerous processes have been developed, the application of sorbents is still one of the most efficient methods to remove heavy metal ions, dyes and crude oil from water. Recently, special attention was paid to sorbents based on natural fibres. A review of studies concerning the sorption properties of wool is presented in this paper. The presence of various functional groups on the wool fibre surface contributes to the efficient sorption of heavy metal ions and dyes. A hydrophobic, scaly surface and fibre crimp strongly influence the high sorption capacity of wool for oil. Wool has great sorption potential even as a recycled material. Accordingly, it can be used as a viable substitute to commercially available synthetic sorbents that show poor biodegradab ility.

New Equipment and Technologies for Treating Effluents, Recycling Oil-Bearing Wastes, and Restoring Oil-Polluted Soils

equipped with treatment plant, which as a rule is substantially worn out and out of date. The water treatment equipment produced in Russia in part fails to meet the standards for effluent purification. Therefore, considerable importance attaches to making up to date local structures for treating industrial and other effluents particularly with circulating water supply. Various technologies are required: • progressive technologies and equipment for upgrading outdated treatment plant; • upgrading local effluent treatment systems by the use of high-performance modular systems; and • development of systems for treating effluents and rain runoff in a unified installation with measures providing circulating water supply. There is a leading Russian organization concerned with developing and manufacturing pressurized flotation equipment for treating effluents, recycling oil wastes, and treating oil-polluted soils, namely the Kursk Institute of Ecological Security (INSTEB), which has constructed and routinely produces a standardized series of high-performance small installations for pressurized flotation (with two-stage and four-stage treatment) with throughput up to 20 m/h in combination with filters for extracting oil products, oils, fats, and suspended organic substances in effluents, as well as hair, surfactants, heavy-metal ions, and also for treating rainwater. Over 350 plants have been built by the Institute and are successfully operated in more than 50 regions of Russia and nearby countries at oil refineries and processing plants, automobile service stations, locomotive and wagon installations, and so on. A design feature in the flotation equipment is concerned with providing all functions from a single pump and twelvefold water recycling, which provides a high degree of purification: 90–95% for suspended materials, 80–95% for fats, and up to 98–99% for oil products. Flotation plant is simple in design and easy to service, and uses little energy and provides circulating water supply while not requiring large areas and major capital investments. Plants have been developed for local use and in larger treatment installations. Figures 1 and 2 show a three-stage treatment flotation plant in regular production and a pressure filter of throughput 5 m/h. Pressurized flotation is a physicochemical method of treatment that involves saturating the effluent with air under pressure and then causing the liquid to bubble by release to atmospheric pressure. Pollutant particles adsorbed on the bubbles are separated and extracted in a foam layer, which is removed. The water is purified to the required standard with mechanical adsorption filters. Flotation plants of the INSTEB series have passed state ecological and public-health tests as registered in Russia. Equipment customers include major Russian oil companies: LUKOIL, YuKOS, Transneft’, TNK, and Tatneft’, as well as organizations in the petrochemical industry (Angara electrochemical plant, or the Neftekhim experimental plant in Ufa), as well as the Ministry of Railroads and many others. Chemical and Petroleum Engineering, Vol. 40, Nos. 1–2, 2004

Purification of Effluents by Two-Aqueous Phase Extraction

The goal of this work is the two-aqueous phase extraction of solutes representing a soluble or dispersed pollution. This is made possible thanks to the phase separation occurring with polyefhoxylated surfactants above the so-called cloud point curve and the solubilization properties of nonionic micelles mainly present in the more concentrated surfactant phase (coacervate). The surfactants used are commercial alcohol ethoxylates (n-C12E4, n-C12E6, Oxo-C10E3 and Oxo-C13E9). The phase diagrams of binary water/surfactant, pseudo-binary (in the presence of solute) and ternary water/surfactant/solute systems were drawn. The last three surfactants were used for the ‘cloud point’ extraction of phenol and benzyl alcohol from their 0.15 wt% aqueous solutions (soluble pollution). The polluted aqueous phase and the surfactant solution were mixed together and separated at room temperature or after heating, according to the cloud point curve of the surfactant. The results are expressed by the four following responses: percentage of solute extracted (E); residual concentrations of solute and surfactant in the dilute phase; and volume fraction of coacervate (ØC) at equilibrium. For each parameter, whose values were determined by an experimental design, these results were the subject of an empirical curve fitting procedure. The best compromise was sought between E, which can be higher than 95%, and (ØC), which must be kept to a minimum (more concentrated pollutant, easier to process). Finally, we applied this extraction technique to two types of mineral cutting oils, used in granite sawing operations. The results are then expressed as chemical oxygen demand (COD) of the dilute phase before and after extraction, and volume fraction of coacervate. For instance, COD can be reduced from 55 to 1.5 g O21–1. Empirical modelling gives a satisfactory agreement between experimental and calculated values.

Buffer distances for on-site sewage systems in Sydney's drinking water catchments

Pathogens and nutrients released from on-site sewage systems represent a risk to surface and ground water quality, particularly where there are sensitive receiving waters such as in drinking water catchments. Buffer zones between on-site systems and waterways are one barrier used to protect water quality. The increased time and distance they provide increases the opportunities for the effluent purification functions of the soil to occur. A risk management model is proposed to assess the efficacy of the buffer zones in Sydney's drinking water catchments. The model is the basis for the development of performance based setback distances for on-site systems from waterways, and incorporates stochastic analysis of pathogen and nutrient transport in the environment and consideration of the effluent quality variability from on-site systems. Catchment-scale integration of contaminant transport is employed to facilitate a risk assessment of on-site systems. The risk management model also allows for the impact of on-site system management and maintenance on catchment water quality to be assessed through scenario building and feedback mechanisms.

Treatment of spent emulsion from a cable factory by an integrated UF/NF membrane system

The potential of using the integrated membrane system based on ultrafiltration (UF) and nanofiltration (NF) in purification of effluents from a cable factory was investigated. The UF experiments were performed using tubular membranes taking into consideration the composition of the treated effluents. The UF process was carried out within the range of parameters recommended for oil emulsion. The application of UF membranes with MWCO of 100 kDa results in the complete rejection of suspended solids and the retention of oil and lubricants at a level of 99%. The UF membranes employed exhibit a 96% passage of copper ions, which is the major component of spent emulsion. The average permeate flux during the UF pretreatment of wastewater produce during copper wire drawing amounts 45 l/m 2h for the transmembrane pressure of 2 bar. The resulting UF permeate was further purified by NF to achieve the retention of remaining pollutants (oil and lubricants) and to reduce the content of copper ions. As a result of the NF process, the content of organic compounds in the permeate determined as TOC was below 1 mg/dm 3, and the rejection of copper ions obtained with the AFC30 membrane was at a level of 92%. The quality of permeate obtained by the application of an UF/NF integrated membrane system allows the direct reuse of treated water for fresh emulsion top up.

Treatment of rainbow trout farm effluents in constructed wetland with emergent plants and subsurface horizontal water flow

The objective of this research was to investigate treatment of aquaculture effluents of flow-through systems in created wetlands. The constructed wetlands types used in this study were subsurface root zone systems with emergent plants and horizontal effluent soil percolation. Three 1.40×1.00×0.70 m ( L× W× H) root zone systems were filled with sands of 1–2 mm particle size and planted with 20 rooted shoots of reed per square meter ( Phragmites australis). Nutrient removal of rainbow trout ( Oncorhynchus mykiss) effluents flowing through the wetland was determined for hydraulic loading rates of 1, 3 and 5 l/min corresponding to very short hydraulic residence times (HRTs) of 7.5, 2.5 and 1.5 h, respectively. Inflowing nutrients were removed within every continuously flooded wetland. Total suspended solids (TSS) and chemical oxygen demand (COD) were reduced by 95.8–97.3% and 64.1–73.8%, respectively, and demonstrated no influence of HRT. Total phosphorus (TP) and total nitrogen (TN) removal rates varied from 49.0% to 68.5% and 20.6% to 41.8%, respectively, and were negatively correlated with HRTs. Effluent purification was best at HRT of 7.5 h, but sufficient removal rates were achieved for shorter HRTs.

Industrial-Scale Electron Beam Purification of Chemically Polluted Wastewaters

First results obtained in the pilot run of an ELV-8 electron accelerator-based technological complex designed for purification of chemically polluted waste effluents from petroleum refineries and petrochemical plants are reported. To provide the effective treatment of the effluents, favorable conditions for the removal of hydrogen sulfide and salt ammonia were found—the initial acidity of pH0 ≤ 7.5 and pH0 ≥ 9.5, respectively. With phenols taken as an example, it was shown that the purification of multicomponent effluents requires a substantially higher power input than in the case of one-component solutions.

Application of the two coupled models for water quality management: facultative pond cum constructed wetland models

Recent work has emphasized the potential importance of the constructed wetland systems for purification of effluents from secondary biological treatment plants for prevention of pollution to the receiving water bodies. A model for transformation of organic carbon in facultative pond (FP) was formulated and was coupled with a model of organic carbon transformation in the constructed wetland (CW) for downstream water resources management. The main essence of coupling the model was to have simultaneous simulation of PFP and CW processes. Simultaneous run of the two models imply that the disturbance on parameters in PFP will have a direct effect on CW processes. The model was formulated on the basis fundamental principle that the growth of active biomass in the system defines the transformation of organic carbon. The growth rate of microorganisms was model based on the Monod kinetic equation. The forcing functions to the model were formulated based on multiplicative function. The removal of organic carbon in the FP based on the unfiltered sample was 66% with an average concentration of 206 mgCOD/l in the effluent. The removal of organic carbon in the CW was 87.5% with an average concentration of 40 mgCOD/l in the effluent. The overall performance of the coupled model was 93%. The main processes of organic carbon removal in the FP and CW were due to uptake by heterotrophic bacteria followed by oxidation. It was found that 80% of the total organic carbon in the CW was due to the biological growth. Oxidation of organic carbon in the PFP was a source of high growth of algae. The constants and coefficients obtained after validation of the model reflect the simultaneous performance of the coupled model of PFP and CW.

Electrodialysis of uranium(VI) through cation exchange membranes and modeling of electrodialysis processes

The transport of ionic species through ion exchange membranes found several applications for water effluents purification and metal ion separation. To enhance the transport performance, the effect of electric fields was suggested in this work. The transport of U(VI) species in nitric acid solutions across cation exchange membranes was investigated. Different parameters affecting the transport of U(VI) were studied. These parameters include: nitric acid concentration in the feed solution, stripping solution concentration and applied electric field. From the results obtained, the cationic flux of U(VI) was 6.5.10–8 geq.cm–2.s–1 at the optimal conditions of 10–3M HNO3 in the feed solution, 0.5M Na2CO3 in the stripping solution and 30 V. The modeling of the electrodialysis process was also made. The model correlates the mass transfer as a function of current density and voltage as variables and takes into account the electro-osmotic effect. The model is applied to the experimental data.

Evaluation of the operational quality of a chemical engineering system for purification of industrial effluents

acteristics of the variation in the input parameters of the system from the dynamic characteristics of the output responses and the dynamic characteristics of the system itself [1–3]. For a chemical engineering system for purification, this means that we need: • to study data on the variability of the concentration of the pollutants in the waste waters; • to determine the dynamic characteristics of the chemical engineering system for purification; • to ensure constancy of the required quality of the treated industrial effluents. A chemical engineering system for purification of industrial effluents containing heavy metal ions, according to the two-stage method we developed, includes (Fig. 1): the equalization process, the mixing process (the first step is neutralization, the second step is presettling); the clarification process, followed by operations for recuperation of the clarified industrial effluents and utilization of the sediment obtained. We should note that the pronounced nonstationary character of the parameters at the inlet to the chemical engineering system determines its dynamic specifications. The degree of complexity of the dynamic operating regime for the chemical engineering system and the purification quality depend directly on this nonstationary character. One method for studying the dynamic situation at the inlet to the chemical engineering system is the spectral statistical analysis method, allowing us to obtain complete information about the spectrum of the fluctuations in the heavy metal ion concentrations in the industrial effluent. We have used data from laboratory studies of industrial effluents containing heavy metal ions from a metalware plant (Southern Urals). As a result of analysis of the data (Fig. 2), we found the following types of nonstationary behavior: – sudden discharges with very high pollutant concentrations (1000 times higher than the zinc MPC [maximum permissible concentration]); – abrupt changes in the pollutant concentration, causing abrupt changes in the load on the purification facilities; – pronounced cyclic behavior of the fluctuations in the pollutant concentration, connected with the cyclic nature of the production processes and work shifts; – the presence of fluctuations with a random spectrum. To evaluate the characteristics of the operation of the chemical engineering system, in this case we will perform a spectral statistical analysis, the first step of which is to obtain a sufficiently representative continuous or discrete record of the pollutant concentration over time. Chemical and Petroleum Engineering, Vol. 37, Nos. 3–4, 2001

Diaphragms and flooding survival

Why don't the gas spaces of submerged organs of wetland plants flood extensively when damaged? In addressing this intriguing question, Soukup et al. (pp. 71–75 in this issue) report on the role of rhizome diaphragms as barriers to flooding in Phragmites australis. This should prompt some reappraisal of the ways in which flooding resistance can be realized, even perhaps in undamaged organs. Most emergent wetland macrophytes have an abundance of interconnected internal gas space, much of it in the form of large voids transversely partitioned at intervals by perforated cellular plates termed diaphragms. Functionally, it provides a low-resistance pathway for internal oxygen transport to support the respiratory needs of submerged and buried organs (Armstrong, 1979; Armstrong et al., 1988; Crawford, 1992) and facilitates carbon dioxide removal. However, it does more than this, since it enables oxygen to be released from the root to where it can support aerobic microbial activity in otherwise anaerobic sediments, and phytotoxin immobilization or destruction (Armstrong et al., 1992; Begg et al., 1994; Gilbert & Frenzel, 1998). This oxygen release is regarded by some as a valuable aid to effluent purification by constructed wetlands. Perhaps a less desirable property of this gas-space provision is its recently discovered role in enhancing the emissions of greenhouse gases such as methane from wetlands (Brix et al., 1992; Chanton & Whiting, 1996; Crutzen, 1991; Dacey & Klug, 1979).

An experimental integrated absorption heat pump effluent purification system. Part II: operating on water/Carrol solutions

An experimental integrated absorption heat pump effluent purification system (IAHPEPS) was built and originally operated with water-lithium bromide as a working mixture. The experimental results of IAHPEPS operated with water-Carrol as a working mixture are presented. Tap water was used as effluent and distilled water was obtained after purification. Pure effluent production rates ranged between 1.2 and 4 kg h −1. The actual coefficient of performance (COP) A varied from 1.35 to 1.55. The heat pump effectiveness (HPE) varied from 0.74 to 0.82. The results from the small scale system indicate the likely results from industrial scale units which could be operated with low quality heat such as waste heat, solar or geothermal resources.

Technology of superconducting magnetic separation in mineral and environmental processing

The conventional magnetic separators used in the mineral industry are equipped with traditional magnetic circuits or with permanent magnets (rare earth). However, when processing minerals with low magnetic susceptibilities or minerals of very small particle size, these separators are inefficient. In addition, a conventional magnetic circuit consumes considerable amounts of electricity to generate a relatively low magnetic field (≈2 Tesla). The equipment is also heavy and bulky. Only a separator having a superconducting solenoid can contribute in solving most of the problems, and only such a separator can produce high magnetic fields with low energy consumption. New developments and the experience acquired in using these superconducting magnets have resulted in new uses for magnetic separation, especially in the environmental area. This paper presents and describes a separation system that uses superconducting magnets that are completely automated and able to treat raw materials (concentration or purification) or liquid industrial effluents containing heavy metals in solution. Several industrial sectors, including the surface treatment, petroleum and chemical industries, are generating effluents containing heavy metal ions. The main metal ions found in such effluents include zinc, copper and vanadium. The purification of such effluents by magnetic separation is performed by adding a certain proportion of iron salts. The treated effluent passes through a superconducting separator where the floes are retained in a matrix of steel wires. The efficiency of supraconducting high-gradient magnetic separation (HGMS) by this method exceeds 95%. Mineral separation and industrial-waste purification results are presented.

Preserving sludge from meat industry waste waters through lactic fermentation

This article presents the results of research on preserving sludge from meat industry waste waters. The sludge precipitated by chemical purification of effluents contains considerable amounts of proteins and fats which under certain conditions can be used for feeding to animals. The preservation of sludge was based on lactic fermentation conducted with the use of Lactobacillus delbrückii. Molasses, as the source of sugars which are necessary in the process of silage, were added to the sludge. Basic conditions for preserving sludge through this method, such as addition of molasses, sludge moisture and fat content, were established. The results of the research imply that silage of sludge from the meat industry effluents can be a good way of preserving sludge and converting it into a fodder.

Filtration and purification of plating and related solutions and effluents

Filtration and purification of plating and related solutions and effluents

Removal of Heavy Metal Ions by Superconducting Magnetic Separation

Several industrial sectors such as surface treatment, petroleum, chemical, etc. generate effluents containing heavy metal ions (HMI). The main metal ions in such effluents can be zinc, copper, vanadium, etc. Purification of such effluents by magnetic separation is performed by adding a certain proportion of iron salts. These salts precipitates together with those of HMI by increasing the pH. The coprecipitation of this “magnetic carrier” with heavy metals hydroxydes to create a magnetic floc has been studied. The effluent treated passes by a superconducting separator where the flocs are retained in a matrix of steel wires. The purified effluent leaves the separator, and the trapped flocs are collected when the matrix is saturated. The efficiency of HMI separation by this method exceeds 95%.

Hazard identification analysis of a hydrogen plant

Process risk analysis is used in industrial activities to diminish accident potential by the application of prevention or protection techniques to improve process safety. For this purpose, Preliminary Hazard Analysis and HAZOP have been applied to a hydrogen gaseous effluent treatment and purification plant. This plant recovers contaminated gaseous effluent hydrogen from a metallurgical iron powder reduction furnace. Purified hydrogen is recycled to the process. The process safety studies included hazard identification and consequences to materials, equipment and people. The study proposed specific process safety measures and future additional process safety studies.

An experimental integrated absorption heat pump effluent purification system. Part I: operating on water/lithium bromide solutions

The merits of single stage absorption heat pumps coupled to simple distillation for effluent treatment are discussed. An experimental integrated absorption heat pump effluent purification system (IAHPEPS) was built and operated with water–lithium bromide as a working mixture. This unit has been used to raise the temperature and hence, the vapour pressure of the impure water contained in one vessel, to the point where pure water vapour will distil from impure effluent solution (tap water or brine) and condense in a second vessel used to collect pure water. Pure effluent production rates of between 0.5 and 4.3 kg h −1 were obtained. The actual coefficient of performance ( COP A) and the heat pump effectiveness varied from 1.1 to 1.4 and 0.58 to 0.72, respectively. The results from the small scale system indicate the likely results from industrial scale units which could be operated with low quality heat such as waste heat, solar or geothermal resources.

Silver catalyzed IBES process: application to a Spanish copper–zinc sulphide concentrate: Part 3. Selection of the operational parameters for a continuous pilot plant

The selection of the operating conditions of a continuous silver catalyzed IBES (Indirect Bioleaching with Effects Separation) process for a chalcopyrite–sphalerite concentrate from Rio Tinto is presented. The data generated from the batch tests have been used to estimate the operating parameters for the continuous system. In order to obtain metal extractions of 94% Zn and 95% Cu, two ferric sulphate leaching stages are necessary: a primary leaching at 70°C with a mean residence time of 8 h divided into five stirred reactors, and a catalytic stage at 70°C and 2.5 mg Ag g −1 concentrate with a mean residence time of 10 h divided into five stirred reactors. The approach is used to develop the complete flowsheet of a pilot plant for the treatment of 50 kg h −1 of this concentrate, including stages of chemical leaching (primary and catalytic), ferrous iron biooxidation, solvent extraction and electrowinning of zinc and copper, elemental sulphur recovery, silver recovery and effluent purification. A preliminary economic evaluation of the process indicates that for an industrial plant of 100,000 t a −1, the direct operating cost would amount to US$141 per ton; the products, copper and zinc, would be worth US$450 per ton and the value of by-products (mainly elemental sulphur and silver) was estimated at US$29 per ton.

Purification of fluorine-bearing effluent and use of the sediment to make exothermic materials

Purification of fluorine-bearing effluent and use of the sediment to make exothermic materials