Synthetic Industrial Wastewater Research Articles

Effect of COD level and HRT on microbial community in a yeast-predominant activated sludge system

This study was conducted to compare the effect of influent chemical oxygen demand (COD in) level and hydraulic retention time (HRT), two primary components of influent COD loading rate (COD LR), on the structure and function of sludge microbial community in a yeast-predominant activated sludge system (1 m H × 0.2 m D) for synthetic industrial wastewater. A combination of polymerase chain reaction-denaturing gradient gel electrophoresis with BIOLOG community-level physiological profiles was used. At higher COD LR and higher COD in and identical HRTs, more microbial species were supported and could metabolise a greater variety of carbon sources in the aerated column. Conversely, a shorter HRT at identical COD in supported fewer microbial species, which resulted in the metabolism of fewer carbon sources.

Electrochemical Treatment of synthetic and Actual Dyeing Wastewaters Using BDD Anodes

In this work, the treatment of synthetic wastewaters containing methylene blue (MB) and rhodamine B (RB) and actual textile wastewaters (ATW) using boron doped diamond (BDD) anodic oxidation was investigated. Voltammetric study has shown that both MB and RB can be oxidized directly at the anode surface in the potential region where the electrolyte salt is stable. Galvanostatic electrolyses of synthetic and actual industrial wastewaters have led to total abatement of COD and TOC at different operating conditions (electrolyte salt and initial pollutant concentration and current density) and the efficiency of the electrochemical process was governed only by mass-transfer limitations. The nature of the supporting electrolyte has a great influence on the rate and the efficiency of the electrochemical oxidation of dyes. The treatment in the presence of NaCl appears to be more efficient in the COD removal, while in the presence of Na2SO4 improves the TOC removal. From the experimental results it seems that the primary mechanisms in the oxidation of dyes are the mediated electro-oxidation by hydroxyl radicals and other oxidants electro-generated from supporting electrolyte oxidation.

Treatment of Synthetic Pesticide Industrial Wastewater with Nanofiltration and Photo-Fenton Oxidation Using Malathion as a Model Substrate

Treatment of Synthetic Pesticide Industrial Wastewater with Nanofiltration and Photo-Fenton Oxidation Using Malathion as a Model Substrate

Optimization of Cr(VI) electroreduction from synthetic industrial wastewater using reticulated vitreous carbon electrodes modified with conducting polymers

In order to maintain high values of current efficiency and space–time yield during the electrochemical reduction of Cr(VI) to Cr(III), a new methodology based on the control of the applied current throughout the process was tested. The electrochemical process was carried out using a reticulated vitreous carbon electrode modified with polyaniline. Experiments to determine the reaction rate of Cr(VI) depletion as a function of current and flow velocities were performed in order to establish the relationship between the transition concentration and these operational variables. The transition concentration was the basis of the optimization procedure proposed here and it is defined as being the concentration where the kinetics changes from linear to exponential concentration dependence. The results demonstrate that for a previously optimized flow velocity, control of the current was very effective in maintaining a high space–time yield down to very low concentrations of Cr(VI) and, consequently, the energy consumption was minimized.

Effect of bio-sludge concentration on the efficiency of sequencing batch reactor (SBR) system to treat wastewater containing Pb 2+and Ni 2+

The removal efficiency of sequencing batch reactor (SBR) system with synthetic industrial estate wastewater (SIEWW) containing Ni 2+ or Pb 2+ was increased with the increase of mixed liquor suspended solids (MLSS). But, the sludge volume index (SVI) of the system was increased up to higher than 100 mL/g under MLSS of up to 4000 mg/L. Also, the effluent NO 3 − was decreased with the increase of MLSS. The heavy metals (Ni 2+ or Pb 2+), BOD 5, COD and TKN removal efficiencies of SBR system with SIEWW containing 5 mg/L heavy metal (Ni 2+ or Pb 2+) under MLSS of 3000 mg/L were 83–85%, 96–97%, 95–96% and 83–94%, respectively. The increase of heavy metal (Ni 2+ or Pb 2+) concentrations of SIEWW from 5 to 50 mg/L were not significantly effected to both COD and BOD 5 removal efficiencies (they were reduced by only 4–5%), but they were strongly effected to both TKN and heavy metals removal efficiencies (they were reduced by 15 and 20–30%, respectively). Both Ni 2+ and Pb 2+ could repress the growth of both nitrification and denitrification bacteria. And Ni 2+ was more effective than Pb 2+ to reduce the heavy metals removal efficiency. The SBR system could be applied to treat the industrial estate wastewater (IEWW) containing both Pb 2+ and Ni 2+ even the heavy metals concentrations was up to 5 mg/L, but the removal efficiency was quite low and excess bio-sludge did not produce. However, the system efficiency could be increased with the increase of BOD 5 concentration of the wastewater. The Pb 2+, Ni 2+, COD, BOD 5 and TKN removal efficiencies of the system with IEWW containing 500 mg/L BOD 5, 5 mg/L Ni 2+ and 5 mg/L Pb 2+ under HRT of 3 days were 85.68 ± 0.31%, 87.03 ± 0.21%, 86.0 ± 0.5%, 94.04 ± 0.4% and 90.5 ± 0.9%, respectively. And the effluent SRT, SS and SVI of the system were 44.7 ± 0.6 days, 150 ± 6 mg/L and 100 mL/g, respectively.

Effects of sorption, sulphate reduction, and Phragmites australis on the removal of heavy metals in subsurface flow constructed wetland microcosms

The removal of Co, Ni, Cu and Zn from synthetic industrial wastewater was studied in subsurface flow constructed wetland microcosms filled with gravel or a gravel/straw mixture. Half of the microcosms were planted with Phragmites australis and half were left unplanted. All microcosms received low-strength wastewater (1 mg L(-1) of Co, Ni, and Zn, 0.5 mg L(-1) Cu, 2,000mg L(-1) SO4) during seven 14-day incubation batches. The pore water was regularly monitored at two depths for heavy metals, sulphate, organic carbon and redox potential. Sorption properties of gravel and straw were assessed in a separate experiment. A second series of seven incubation batches with high-strength wastewater (10 mg L(-1) of each metal, 2,000 mg L(-1) SO4) was then applied to saturate the substrate. Glucose was added to the gravel microcosms together with the high-strength wastewater. Sorption processes were responsible for metal removal during start-up, with the highest removal efficiencies in the gravel microcosms. The lower initial efficiencies in the gravel/straw microcosms were presumably caused by the decomposition of straw. However, after establishment of anaerobic conditions (Eh approximately -200 mV), precipitation as metal sulphides provided an additional removal pathway in the gravel/straw microcosms. The addition of glucose to gravel microcosms enhanced sulphate reduction and metal removal, although Phragmites australis negatively affected these processes in the top-layer of all microcosms.

Impact of Selected Pollutants in Synthetic Industrial Wastewater on Nitrifying Biofilms in Fixed Bed Biofilm Reactors‐Visualized with Fluorescence In‐Situ Hybridization

The impact of selected pollutants on the structure and activity of nitrifying bacterial populations within fixed bed biofilm reactors was examined. Clofibrinic acid and ibuprofen as pharmaceutically active compounds were added to a synthetic wastewater fed to the biofilm reactors and the concentrations of chloride and dissolved organic carbon were also varied. Clear impacts of increased salt and dissolved organic carbon concentrations on nitrification activity and nitrifying bacterial populations were observed whereas clofibrinic acid (up to 100 µg/l) and ibuprofen (10 µg/l) showed no impact on the nitrification activity. The exposure to clofibrinic acid also showed no significant influence on the nitrifying bacterial population, while the addition of ibuprofen resulted in a slight shift of the population to a lower abundance of the β‐proteobacteria.

Removal of Pb 2+ and Ni 2+ by bio-sludge in sequencing batch reactor (SBR) and granular activated carbon-SBR (GAC-SBR) systems

Living bio-sludge from domestic wastewater treatment plant was used as adsorbent of heavy metals (Pb 2+, Ni 2+) and its adsorption capacity was about 10–30% reduced by autoclaving at 110 °C for 10 min. The living bio-sludge acclimatized in synthetic industrial estate wastewater (SIEWW) without heavy metals showed the highest Pb 2+ and Ni 2+ adsorption capacities at 840 ± 20 and 720 ± 10 mg/g bio-sludge, respectively. The adsorbed Pb 2+ and Ni 2+ were easily eluted (70–77%) from bio-sludge by washing with 0.1 mol/l HNO 3 solution. The heavy metals (Pb 2+, Ni 2+) removal efficiency of both SBR and GAC-SBR systems were increased with the increase of hydraulic retention time (HRT), or the decrease of organic loading. The SBR system showed higher heavy metals removal efficiency than GAC-SBR system at the same organic loading or HRT. The Pb 2+, Ni 2+, BOD 5, COD and TKN removal efficiencies of GAC-SBR system were 88.6 ± 0.9%, 94.6 ± 0.1%, 91.3 ± 1.0%, 81.9 ± 1.0% and 62.9 ± 0.5%, respectively with industrial estate wastewater (IEWW) with 410 mg/l glucose, 5 mg/l Pb 2+ and 5 mg/l Ni 2+under organic loading of 1.25 kg BOD 5/m 3 d (HRT of 3 days). The bio-sludge quality (sludge volume index: SVI) of the system was less than 80 ml/g. The excess sludge from both SBR and GAC-SBR systems with SIEWW under the organic loading of 1.25–2.50 kg BOD 5/m 3 d contained Pb 2+ and Ni 2+ at concentrations of 240–250 mg Pb 2+/g bio-sludge and 180–210 mg Ni 2+/g bio-sludge, respectively.

Removal of Zn 2+ and Cu 2+ by a sequencing batch reactor (SBR) system

Both resting (living) and autoclaved (dead) bio-sludges showed almost the same Cu 2+ and Zn 2+ adsorption capacities with synthetic industrial estate wastewater (SIEWW). The resting bio-sludge showed not only Cu 2+ and Zn 2+ adsorption abilities but also organic matter adsorption ability. But, the organic matter (COD and BOD 5) adsorption ability of bio-sludge with SIEWW containing 60 mg/L Cu 2+ was about half of that with SIEWW containing 60 mg/L Zn 2+. The adsorbed Cu 2+ and Zn 2+ were easily eluted (70–75%) from bio-sludge with 0.1 N HNO 3 and 0.1 M EDTA solutions. Bio-sludge from a wastewater treatment plant could be used as an adsorbent for metal ions (Cu 2+ and Zn 2+). Cu 2+ and Zn 2+ could repress the SBR system efficiency but its efficiency could be increased with the increase of mixed liquor suspended solids (MLSS), and Cu 2+ had more effect than Zn 2+ to repress the system efficiency. The SBR system showed very low removal efficiencies of the pollutants with industrial estate wastewater (IEWW), but its pollutant removal efficiencies with IEWW could be increased with the addition of glucose. The Zn 2+, Cu 2+, BOD 5, COD and TKN removal efficiencies of the system with IEWW containing 1.27 g/L glucose, 10 mg/L Cu 2+ and 10 mg/L Zn 2+ under MLSS of 4500 mg/L were 92.61 ± 0.28%, 83.77 ± 0.93%, 98 ± 0%, 92 ± 0% and 78.1 ± 0.1%, respectively.

Detoxification of synthetic industrial wastewaters using electrochemical oxidation with boron‐doped diamond anodes

AbstractThe electrochemical oxidation on boron‐doped diamond (BDD) anodes of synthetic industrial wastewaters polluted with different aromatic compounds has been studied. This technology reduces significantly the organic load and the toxicity of treated aqueous wastes. The shape of the toxicity vs time curve depends strongly on the nature of the phenolic compounds, and especially on the substituent groups contained in the phenol molecule. For the oxidation of hydroxybenzenes a complex shape is obtained, with a plateau zone in the first stages of the electrolyses. This plateau zone is transformed into a maximum in the electrolyses of chlorophenols. In the case of nitrophenols, the toxicity index decreases at the same time as the chemical oxygen demand (COD) concentration, although the decrease in the toxicity is less significant than the decrease in the COD. All these toxicity profiles can be justified in terms of the nature of the intermediates generated during the electrolyses, but they cannot be directly related to the COD variation, which shows an exponential decrease. Copyright © 2005 Society of Chemical Industry

Light emitting diodes and an infrared bulb as light sources of a fixed‐film tubular photobioreactor for conversion of hydrogen sulfide to elemental sulfur

AbstractThe effect of light quality on the performance a fixed‐film continuous‐flow photobioreactor for removal of hydrogen sulfide from synthetic industrial wastewater and conversion of it to elemental sulfur was investigated. Sixteen 150 mm long and 1.6 mm internal diameter (id) Tygon tubes formed the active part of the reactor. At the same light intensity, reactor performance in terms of optimal sulfide loading rates was compared between an infrared bulb and light emitting diodes (LEDs). The LEDs provided light within the peak absorption wavelength range of green sulfur bacteria (GSB) and were used as a light source for the GSB with the goal of reducing the cost of the required light. Though the reactor sustained higher sulfide loading rates using LEDs than when using an infrared bulb at equal light intensities, the infrared bulb has the potential to be more efficient overall. Copyright © 2004 Society of Chemical Industry

Microbial community structure and methanogenic activity during start-up of psychrophilic anaerobic digesters treating synthetic industrial wastewaters

Culture-independent, molecular techniques were applied to the characterization of microbial communities of an anaerobic granular sludge obtained from a full-scale digester. Procedures were optimised for total DNA recovery and polymerase chain reaction (PCR) amplification of 16S rDNA using archaea- and eubacteria-specific oligonucleotide primers. Cloned PCR products were subsequently screened by amplified rDNA restriction analysis to identify operational taxonomic units (OTUs). Inserts from clones representing each OTU were sequenced and phylogenetic trees were prepared. In addition, the microbial communities were characterised using terminal restriction fragment length polymorphism (T-RFLP). The specific methanogenic activity of the biomass, against various substrates, was also ascertained. Two anaerobic bioreactors were seeded with granular and non-granular (i.e. crushed) aliquots of the characterised sludge, respectively, and used to investigate the treatment of a volatile fatty acid (VFA)-based synthetic wastewater, at a loading rate of 5 kg COD m −3 day −1 at low ambient temperatures (18°C). DNA was isolated from sludge samples during the test period and shifts in archaeal and eubacterial population structures were elucidated. The start-up period was successful with methane yields and COD removal efficiencies of 60–75% and 65–85%, respectively. Specific methanogenic activities of reactor biomass, obtained at the conclusion of the trial, indicated the development of psychrotolerant biomass during the 90-day experiment. Furthermore, the efficacy of T-RFLP as a molecular tool for use in the surveyance of engineered ecosystems was confirmed.

Treatment of synthetic industrial wastewater with [formula omitted] and RO using benzene as a model hydrocarbon

Contamination of water resources with hazardous chemicals is one of the main concerns of all private and public sectors involved in the water production for drinking, irrigation and domestic use. The conventional disinfection process using chlorination adds to the complexity of the problem as some of these chemicals are precursors for disinfection by products such as trihalomethanes. This paper describes the work done to study the efficiency of two types of processes in removing a model hydrocarbon, namely, benzene, which was added to water at a concentration of 100 ppm. The two processes investigated were RO and UV/TiO 2 The RO process was based on a FilmTec SW30 spiral wound membrane, which was operated at pressures of 20,40 and 60 bar. The UV/TiO 2 employed was PhotoCat, manufactured by Purifics, Canada. The heart of the PhotoCat unit was 32 low pressure, low intensity mercury vapor lamps connected in series. Gas chromatography was used to analyze the results. The results showed that the UV/TiO 2 resulted in a removal of 99.28%. However, the RO performance was less impressive with a maximum separation of 82.3%. At 40 bar, a negative permeability was observed, as the concentration of benzene in the permeate was higher than the feed. This latter result shows that care has to be taken with hydrocarbons polluting the feed water to RO units, since in certain cases the product water will more polluted than the feed.

Effect of tube size on performance of a fixed-film tubular bioreactor for conversion of hydrogen sulfide to elemental sulfur

A fixed-film continuous-flow photobioreactor was used for the removal of hydrogen sulfide from synthetic industrial wastewater and conversion of it to elemental sulfur using sixteen 150 mm length Tygon tubes as the active part of the reactor. Three different tube sizes (internal diameters (ID) 6.4, 3.2, and 1.6 mm) were used to investigate the effect of tube size on reactor performance. The reactor with 1.6 mm tube attained a higher sulfide loading (1451 mg/L h) than previously reported in the literature. High bacterial concentration, light to volume ratio and intimate contact between attached bacteria and influent sulfide resulted in excellent performance of the 1.6 mm tube reactor.

Biological conversion of hydrogen sulphide to elemental sulphur in a fixed-film continuous flow photo-reactor

The green sulphur bacterium Chlorobium thiosulfatophilum was used to remove hydrogen sulphide from synthetic industrial wastewater and convert it to elemental sulphur in a fixed-film continuous-flow photosynthetic bioreactor. Twenty 150 mm×3 mm ID Tygon tubes formed the active part of the reactor resulting in a total volume of 21.2 mL. Seven steady states were achieved under different experimental conditions using this tubular photo-reactor. Sulphide loading rates ranged from 111 to 328 mg/h L under influent flowrates of 9.0–42.4 mL/h and hydraulic retention times of 0.50–2.35 h. The irradiance at the reactor surface averaged 25.4 W/m 2. The sulphide removal rates were found to be 82–100 % and elemental sulphur recovery rates were found to be 75–95%. The maximum sustainable sulphide loading rate was found to be 286 mg/h L, which is 2.5 times higher than the previous reported highest value. Sulphide loading rate was found to be the function of radiant flux per unit reactor volume and the bacteriochlorophyll concentration as expressed by the van Niel curve.

Simultaneous removal of carbon, nitrogen and phosphorus from wastewater by coupling two-step anaerobic digestion with a sequencing batch reactor

The objective of this study was to develop an integrated process for simultaneous removal of carbon, nitrogen and phosphorus from industrial wastewaters. The process consisted of a-two step anaerobic digestion reactor, for carbon removal, coupled with a sequencing batch reactor (SBR) for nutrient removal. In the proposed process, carbon is eliminated into biogas by anaerobic digestion: acidogenesis and methanogenesis. The volatile fatty acids (VFA) produced during the first step of anaerobic digestion can be used as electron donors for both dephosphatation and denitrification. In the third reactor (SBR) dephosphatation and nitrification are induced through the application of an anaerobic–aerobic cycle. This paper describes the first trials and experiments on the SBR and a period of 210 days during which the SBR was connected to the acidogenic and methanogenic reactors. It was shown that nitrification of ammonia took place in the SBR reactor, during the aerobic phase. Furthermore, denitrification and VFA production were achieved together in the acidogenic reactor, when the efflux of nitrates from the SBR reactor was added to the first reactor influx. The proposed process was fed with a synthetic industrial wastewater, the composition of which was: total organic carbon (TOC)=2200 mg dm−3, total Kjeldahl nitrogen (TKN)=86 mg dm−3, phosphorus under phosphate form (P-PO4)=20 mg dm−3. In these conditions, removals of carbon, nitrogen and phosphorus were 98%, 78% and 95% respectively. The results show that the combination of the two-step anaerobic digestion reactor and an SBR reactor is effective for simultaneous carbon, nitrogen and phosphorus removal. Reactor arrangements enabled zones of bacterial populations to exist. Complete denitrification occurred in the acidogenic reactor and hence the anaerobic activity was not reduced or inhibited by the presence of nitrate, thus allowing high TOC removal. Stable phosphorus release and phosphorus uptake took place in the SBR after coupling of the three reactors. A fast-settling compact sludge was generated in the SBR with the operational conditions applied, thus giving good separation of supernatant fluid. The benefits from this process are the saving of (i) an external carbon source for denitrification and phosphorus removal, (ii) a reactor for the denitrification step. © 1998 Society of Chemical Industry

Extraction of zinc in an Oldshue-Rudston column by liquid surfactant membranes

The extraction of metal ions by liquid surfactant membranes (LSM) leads to high enrichment factors in the internal phase and very low concentration of metal ions in the external phase. Therefore the liquid membrane technique is very useful in hydrometallurgy and wastewater treatment. Recently, the extraction of zinc by LSM has been investigated [ l-51. In this paper, the results of extraction of zinc by LSM from synthetic solutions and real industrial wastewater are presented. The results of continuous extraction show that the zinc concentration in the feed solution can be reduced from 200 ppm to less than 5 ppm, giving a zinc concentration in the internal phase (receiving phase) of more than 10 g/l. The oil phase (liquid membrane phase) can be reused for preparing emulsion. The content of hydrocarbon in the raffinate is less than 7.5 ppm, which is less than the discharge standard. Laboratory scale experiments demonstrate that LSM provide a novel technique for the recovery of zinc from dilute industrial wastewater.

Water Treatment by Means of Activated Carbon, Prepared from Locally Available Waste Materials (II)

Man's natural water supplies are threatened by a large number of nonbiodegradable and toxic organic compounds. Proper environmental standards often can only be attained using tertiary treatment processes, such as adsorption on activated carbon. The latter is an expensive process, owing to the initial cost of activated carbon and the losses occurring during regeneration. Methods are being investigated at the Free University of Brussels for producing and activating carbon, using various types of waste as a raw material. Following materials have already been used : cacao hulls, sawdust, fruit stones, bark, and waste tyres. Both carbonization and activation have been conducted under the carefully controlled conditions of a fluidized bed reactor. The influence of the following process parameters has been investigated : pyrolysis temperature and time, activation temperature and time, and composition of the furnace atmosphere. The resulting activated carbons should exhibit the following qualities : high adsorption capacity and rate, good resistance to attrition, and possibility of regenerating the carbon. The properties of the carbon obtained have been evaluated by means of a number of standard tests (Iodine-index, BET-surface, Tannin-index, Methylene blue-index, and Phenol-index), and adsorption isotherms of phenol, pentachlorophenol, p. toluene sulphonate and dodecyl benzenesulphonate. In general the properties of the carbons obtained were comparable to those of commercial qualities. Some of the activated carbons tested will soon be evaluated using synthetic and real phenolic industrial wastewaters (1.5 % of phenol).

The removal of heavy metals from industrial effluents in a biological fluidised bed

Abstract More than 90 % of Cadmium can be continuously abstracted from synthetic industrial wastewater flowing through a biological fluidised bed. The removals of Zinc, Lead and Copper reach the same order of magnitude. Moreover, all these metals are concentrated in biologically coated‐sand particles i.e. in a small volume which could be easily collected.