Effects of Combined Chemical and Biological Treatments on the Degradability of Vulcanization Accelerators

An investigation was made into a novel system aimed at reducing the impact of highly polluting wastewaters, and based on the combined action of catalytic oxidation and microbial biotechnology. The experimental part incorporated the following three schemes: chemical treatment using Fenton’s reaction for a single process (stage 1); biological treatment only (stage 2); and chemical oxidation followed by biological treatment (stage 3). Wastewaters with 2-mercaptobenzothiazole (MBT; 7,200–7,400 mg O₂ l^?1) were oxidized by stoichiometric amounts of dilute hydrogen peroxide (35%) in the presence of water soluble iron catalysts, either Fe (II) or Fe (III), at concentrations up to 1% w/w and above. As a result, transformation by chemical means of recalcitrant organics to more easily attackable end-products occurs, that can subsequently undergo conventional or advanced (microflora and biomass dispersed or adhered) biological treatments, with 90% of chemical oxygen demand abatement and 95% of MBT.     

Nitrogen And Phosphorus Removal In Substrate-Free Pilot Constructed Wetlands With Horizontal Surface Flow In Uganda

In constructed wetlands (CWs) with horizontal sub-surface flow, nutrient removal, especially phosphorus, is limited because the root biomass fills the pore spaces of the substrate (usually gravel), directing wastewater flow to deeper wetland media; plants are not regularly harvested; the litter formed by decomposing vegetation remains on the surface of the substrate and thus does not interact with the wastewater; and the substrate media often used provide only limited adsorption. Effective nutrient removal including rootzone oxidation, adsorption and plant uptake therefore requires sufficient interaction of wastewater with the treatment media. We assessed the feasibility of biological nutrient removal from wastewater using substrate-free CWs with horizontal flow, planted with two tropical macrophytes namely, Cyperus papyrus and Miscanthidium violaceum. The objectives were to evaluate the system treatment efficiency under semi-natural conditions, and to assess microbial and plant biomass contributions to nutrient removal in the CWs. Results showed high removal efficiencies for biochemical oxygen demand, ammonium-nitrogen (NH₄–N) and phosphorus (P) fractions in papyrus-based CWs (68.6–86.5%) compared to Miscanthidium (46.7–61.1%) and unplanted controls (31.6–54.3%). Ammonium oxidizing bacteria in CW root–mats (10⁸–10⁹ cells/gram dry weight) and residual nitrite and nitrate concentrations in the water phase indicated active system nitrification. Papyrus showed higher biomass production and nutrient uptake, contributing 28.5% and 11.2%, respectively, of the total N and P removed by the system compared to 15% N and 9.3% P removed by Miscanthidium plants. Compared to literature values, nitrification, plant uptake and the overall system treatment efficiency were high, indicating a high potential of this system for biological nutrient removal from wastewaters in the tropics.     

Fate of Amoxicillin In Two Water Reclamation Systems

The overall objective of this research was to determine the fate of amoxicillin in two wastewater reclamation systems containing biological and physical/chemical treatment processes. The results of this study indicate that amoxicillin is easily removed in a biological wastewater treatment system (<0.15 and 0.10 mg/L). Further evaluation of the physical/chemical treatment process, which included reverse osmosis, ion exchange, and UV oxidation and disinfection, indicated that amoxicillin will be removed (<0.10 mg/L) should it breakthrough the biological system. The concern of amoxicillin is not its presence in high concentrations in the effluent of a water reclamation system, but low antibiotic concentrations, which are known to encourage antibiotic resistance development.     

Chemical pretreatment of olive oil mill wastewater using a metal-organic framework catalyst

Olive oil mill wastewaters (OOMW) are not suited for direct biological treatment because of their nonbiodegradable and phytotoxic compound (such as polyphenols) content. Advanced technologies for treatment of OOMW consider mainly the use of solid catalysts in processes that can be operated at room conditions. A system based on combined actions of catalytic oxidations and microbial technologies was studied. The wet hydrogen peroxide catalytic oxidation (WHPCO) process is one of the new emerging oxidation processes particularly attractive for the pretreatment of highly polluted OOMW containing polyphenols that are not suited for classical treatments. In this work, the biodegradability of OOMW was evaluated before and after treating the wastewater samples by the WHPCO process using a metal-organic framework (MOF) as a catalyst. This material, containing Cu and prepared with benzene-1,3,5-tricarboxylic acid (BTC), is a robust metal-organic polymer with a microporous structure that is reminiscent of the topology of zeolite frameworks.     

Application of an Air Ionization Device Using an Atmospheric Pressure Corona Discharge Process for Water Purification

Pesticides presently being discharged into the aquatic environment are not only toxic but also only partially biodegradable, they are not easily removed by conventional water treatment plants. Air ionization devices using an atmospheric pressure corona discharge process show great promise in improving degradation of chemical and biological contaminants in water purification plants. In order to assess the effectiveness of this air ionization apparatus, laboratory scale degradation experiments were carried out systematically in a bubble column reactor containing a variety of pesticides such as triazines, carbamates, phenyl urea derivates and chlorophenols relative to the addition of humic acid and inorganic chemicals as well as to pH variation. Chemical oxygen demand (COD) decreased with air ionization treatment and the rate of the biological oxygen demand related to this (BOD/COD) showed improved pesticide biodegradability. Changes in water toxicity were monitored by Daphnia- and Luminescence Bacteria tests. This novel water treatment process is shown to be a potent oxidation technique for persistent organic pollutants such as pesticides.     

Treatment of Domestic Wastewater by Enhanced Primary Decantation and Subsequent Naturally Ventilated Trickling Filtration

To treat household wastewater, a sequence of ‘primary decantation–trickling filter percolation’ was applied in a lab-scale designed treatment system. Poly-electrolyte was used as coagulant to enhance the primary treatment and charcoal was used as carrier material in the trickling filters. Oxygen was supplied to the trickling filters by means of natural ventilation. In the lab-scale system, the enhanced primary stage removed more than 91% of the suspended solids (SS), and 79% of the total chemical oxygen demand (CODt). The subsequent trickling filtration brought a complete nitrification to the wastewaters at a volumetric loading rate (Bv) of 0.7–1.0 g CODt L^-1 d^-1. On average, the concentrations of the CODt and SS in the final effluents were about 55 and 15 mg L^-1 respectively. With respect to phosphate, physico-chemical removal was the dominant process. About 46–62% of total P was removed from the tested wastewaters. The integrated treatment system also achieved a fair degree of hygienisation. The numbers of total coliforms, fecal coliforms and fecal streptococci were decreased by 2–4 log units. The sludge production of the entire treatment system was about 1.7% (v/v) of the treated wastewater. Only primary sludge was produced; secondary sludge produced in the trickling filters was negligible. The cost savings in terms of minimization of sludge production and aeration energy are estimated to be substantial (i.e. some 50%) relative to a conventional activated sludge system.     

Wastewater Treatment Performance of Rotating Perforated Tubes Biofilm Reactor with Liquid Phase Aeration

A novel biofilm reactor named as `rotating perforated tubes biofilm reactor' was used for treatment of synthetic wastewaterwith and without liquid phase aeration. Effects of major processvariables such as feed wastewater flow rate, COD concentration and loading rate, liquid phase aeration on the rate and extent ofCOD removal were investigated. Liquid phase aeration was provento be advantageous especially for high strength wastewaters at highCOD loading rates. Kinetics of COD removal was investigated andkinetic constants were determined by using the experimental data.An empirical design equation was developed to quantify the system's performance as a function of major process variables.     

Enhanced Phenol and Chlorinated Phenols Removal by Combining Ozonation and Biodegradation

Water treatment for wastewater containing phenols and their chlorinated variations has attracted important research efforts. Phenol??s high toxicity makes them a good model to test possible water treatment based on biological and/or chemical methods. High concentrations of phenols may be treated by pure biological schemes. However, chlorinated phenols are very toxic for many microorganisms. Therefore, mixed treatment trains can be proposed to solve the treatment of this class of organics. In this study, the ozonation was used as pretreatment to decompose chlorinated phenols. Besides, this study describes how the microbial consortiums were adapted to handle ozonation by-products. The biodegradation of different phenol concentrations from 50 to 1,500?mg/L was evaluated using preadapted microbial consortia in batch and in a trickling packed-bed reactor (TPBR). Under batch conditions, phenol was efficiently removed up to 500?mg/L. For every phenol concentration evaluated, higher degradation rates were obtained in TPBR. The chlorophenols were found to be poorly degraded by the pure biological treatment, 4-CPh was not degraded during the biological process and 2,4-DCPh was only 40?% degraded after 250?h of culture. By combining the chemical (as pretreatment) and the biological processes, 85?% of 4-CPh was removed, while the degradation of the 2,4-DCPh was enhanced from 40 to 87?%. The predominant bacteria found in the preadapted cultures were Xanthomonas sp., Ancylobacter sp., and Rhodopseudomonas. Total treatment period was reduced from several weeks to some days. This information reflects the benefits offered by the mixed water treatment train proposed in this paper.     

Mineral-catalyzed peroxidation of tetrachloroethylene

The treatment of perchloroethylene (PCE) was investigated by the promotion of Fenton-like reactions using the iron oxyhydroxide goethite (α-FeOOH) as the sole source of the iron catalyst. A silica sand-goethite matrix was contaminated with 5 mg L^?1 PCE and the oxidative treatments were conducted with 0.15 mM, 2 mM, 5mM, 10mM, 20mM, and 30mM H₂O₂. Perchloroethylene was effectively degraded within 96 hr and the most efficient treatment stoichiometry was observed using 0.15 mM H₂O₂ at pH 3. The degree of heterogeneous catalysis was evaluated by conducting oxidation reactions in parellel systems with an equivalent concentration of soluble iron. The results showed that, within the first 24 hr, up to 94% of the PCE degradation was attributed to heterogeneous catalysis. This modified Fenton's process, when used to treat 5 mg L^?1 PCE in natural subsurface materials with 2 mM H₂O₂ at pH 3, resulted in a residual of 0.20 mg L^?1 PCE after 96 hr.     

Sequential solar photo-fenton-biological system for the treatment of winery wastewaters

In this study, winery wastewaters are considered for degradation using heterogeneous photo-Fenton as a preliminary step before biotreatment. The heterogeneous photo-Fenton process assisted by solar light is able to partially degrade the organic matter present in winery wastewaters. When an initial hydrogen peroxide concentration of 0.1 M is used over 24 h of treatment, a degradation yield of organic matter (measured as TOC) of around 50% is reached. The later treatment (activated sludge process) allows the elimination of 90% of the initial TOC present in pretreated winery wastewaters without producing nondesired side-effects, such as the bulking phenomenon, which is usually detected when this treatment is used alone. The final effluent contains a concentration of organic matter (measured as COD) of 128 mg O2/L. The coupled system comprising the heterogeneous photo-Fenton process and biological treatment based on activated sludge in simple stage is a real alternative for the treatment of winery wastewater.     

Treatment of High Ammonium–Nitrogen Wastewater from Composting Facilities by Air Stripping and Catalytic Oxidation

Composting municipal wastewater sludge may generate composting wastewater (acid washer water and tunnel wastewater) with high ammonium–nitrogen (NH₄–N) concentration; this kind of wastewater is usually generated in a rather small daily amount. A procedure of air stripping with catalytic oxidation was developed and tested with pilot-scale and full-scale units for synthetic disposal of the high NH₄–N wastewaters from composting facilities. In air stripping, around 90% NH₄–N removal efficiency was reliably achieved with a maximum of 98%. A model to describe the stripping process efficiency was constructed, which can be used for process optimization. After catalytic oxidation, the concentrations in the outlet gas were acceptable for NH₃, NO_X, NO₂, and N₂O, but the NH₃ and N₂O concentrations limited the feasible loading range. The treatment costs were estimated in detail. The results indicate that air stripping with the catalytic oxidation process can be applied for wastewater treatment in composting facilities.     

Reduction in the Acute Toxicity of Explosive Wastewater Containing Toxic Nitroaromatic Compounds by a Nanoscale Zerovalent Iron Pretreatment Process

The feasibility of using nanoscale zerovalent iron (nZVI) treatment for reducing the acute toxicity of explosive wastewater, such as 2,4,6-trinitrotoluene (TNT) red water which contains highly toxic nitroaromatic compounds (NACs), has been investigated. The water quality was evaluated before and after nZVI treatment using several different analytical techniques, including UV?CVis spectroscopy, X-ray photoelectron spectroscopy, high-performance liquid chromatography, and gas chromatography/mass spectroscopy. The acute toxicity of the wastewater was tested using a luminescence bacterium bioarray. The results indicated that the most significant toxic NACs, such as dinitrotoluene sulfonates, had been effectively removed from the TNT red water by nZVI together with the small amounts of other NACs. Following 1?h of the nZVI processing treatment, the acute toxicity of the TNT wastewater was reduced by approximately 94?%. This treatment would therefore be useful for the pretreatment of wastewaters prior to the application of a biological process. The reduction in the biotoxicity of the wastewater was based on the reductive conversion processes and adsorption behaviors of nZVI.     

Olive oil mill wastewater treatment using a chemical and biological approach

Olive oil mill wastewaters (OMW) are recalcitrant to biodegradation for their toxicity due to high values of chemical oxygen demand (COD), biological oxygen demand (BOD), and phenolic compounds. In the present study OMW, collected in southern Italy, were subjected first to a chemical oxidative procedure with FeCl3 and then to a biological treatment. The latter was performed in a pilot plant where mixed commercial selected bacteria, suitable for polyphenols and lipid degradation, were inoculated. The effect of treatments was assessed through COD removal, reduction of total phenols, and decrease of toxicity using primary consumers of the aquatic food chain (the rotifer Brachionus calyciflorus and the crustacean Daphnia magna). The results showed that the chemical oxidation was efficacious in reducing all parameters analyzed. A further decrease was found by combining chemical and biological treatments.     

Organic matter bound to mineral surfaces: Resistance to chemical and biological oxidation

Understanding the turnover of organic matter (OM) in soils necessitates information on biological stability and ecological functions. For easy characterization of slowly cycling OM, treatments using oxidants such as sodium hypochlorite (NaOCl) have been applied. The rationale for that approach is, however, questionable and concerns exist to which extent abiotic oxidation can mimic biological mineralization. Here we compare biological mineralization of mineral-bound OM to its resistance to chemical oxidation by 6 mass% NaOCl. Water-extractable OM, sorbed to goethite, vermiculite, and pyrophyllite at pH 4.0 and in different background electrolytes (CaCl₂, NaCl, NaCl-NaH₂PO₄) to favor or exclude certain binding mechanisms, was subsequently subjected to NaOCl treatment (pH 7, either for 18 or 6 × 6 h). Irrespective of mineral surface properties and mechanisms involved in OM sorption, NaOCl removed a constant portion of the sorbed OC. More OC survived when bound to goethite than to vermiculite, thus confirming previous results on the increase of oxidation-resistant OC with increasing Fe and Al (hydr)oxide contents in different soils. Mineralizable OC (within 90 days) was much smaller than the NaOCl-removable OC and both fractions were negatively correlated (r² = 0.90 for the 18 h treatment; r² = 0.86 for the 6 × 6 h treatment), suggesting that chemically oxidizable OM does not represent the portion of sorbed OM available to biological consumption.     

Biological treatment of pharmaceutical wastewater

A study of physicochemical and biological treatment of pharmaceutical wastewater by the activated sludge process was performed in an oxidation ditch. The physicochemical study using different coagulants revealed that all the coagulants used are not effective and their doses required were very high for COD reduction. In the biological oxidation study, it was found that the wastewater could be processed at all organic loadings and phenol concentrations encountered in wastewater. The yield coefficient and decay coefficient were 0.75 (COD basis) and 0.01 day^?1 (COD basis), respectively.     

Degradation of Di-(2-ethylhexyl) Phthalate (DEHP) by TiO2 Photocatalysis

The photocatalytic degradation of di-(2-ethylhexyl) phthalate (DEHP) in solution using titanium dioxide (TiO₂) was analyzed in this study. It was found that DEHP was completely removed in the solution after 150 min irradiation. The effect of different factors, such as photocatalyst amount, DEHP concentration, light intensity, pH, and temperature on photocatalytic degradation was investigated. The degradation mechanism of DEHP with proton and hydroxyl radicals oxidation were also studied. It is suggested that either ethylhexyl or ester chain scissions of the aliphatic part of DEHP was the dominant degradation mechanism of the process. The photocatalytic degradation process was well described by first-order reaction. The final mineralization product was carbon dioxide and the intermediate products were identified by GC-MS. Thus, the photocatalytic degradation treatment of DEHP in wastewater is a relative simple and fast method.     

Characterization of betacyanin oxidation catalyzed by a peroxidase from Beta vulgaris L. roots

A protein fraction with peroxidase (EC 1.11.1.7) activity against guaiacol from Beta vulgaris L. roots oxidized both betanidin and betanin (betanidin 5-O-beta-D-glucoside), the former being the more efficient substrate for the enzyme. The protein fraction contained three strongly basic perxidase isoenzymes. Betanidin quinone was formed as the only product in the course of enzymatic betanidin oxidation, whereas betalamic acid and several oxidized cyclo-DOPA 5-O-beta-D-glucoside polymers were generated during the oxidation of betanin. In accordance with the catalytic properties of peroxidase, a possible mechanism for betanidin oxidation is proposed. This mechanism includes the formation of a betanidin radical, which, by further dismutation, yields betanidin quinone and betanidin. The betanidin oxidation rate showed a Michaelis-type dependence on the substrate concentration. The apparent K(M) for the reaction was 0.46 mM. On the basis of the spectral properties of the enzyme responsible for both betanidin and betanin oxidations, its peroxidase nature is suggested.     

Chemical and Biological Combined Treatments for the Removal of Pesticides from Wastewaters

The combination of chemical oxidation (Fenton reaction) and biological treatment processes is a promising technique aiming to reduce recalcitrant wastewater loads. Preliminary tests were carried out on two widely used toxic and non-biodegradable pesticides, namely, Dazomet and Fenamiphos. The chemical reaction was employed as a pre-treatment step for the conversion of the substrates into oxygenated intermediates that were easily removed by means of a final biological treatment. In the combined action, the mineralisation activity of a selected microbial consortium was used to degrade residual volatile and non-volatile organic compounds into CO₂ and biomass.     

Biological Denitrification of Groundwater

Nitrate concentrations in groundwater have increased in many areas of the world. This causes serious concerns because of the link found between nitrate and the blue-baby syndrome, and of the possible formation of carcinogenic compounds in the digestive tract. Biological denitrification, bacteria-mediated reduction of nitrate to nitrogen gas, is a method used in the treatment of nitrate contaminated groundwater. The denitrifying microorganisms require carbon and energy substrates which may be organic or inorganic compounds. Treatment can take place in the aquifer (in situ treatment) or in above ground reactors. Numerous biological denitrification processes have been reported; this paper reviews some of this work and studies in progress in the author's laboratory. The choice of a biological denitrification system has to be considered on an individual basis. Although preventive measures are curbing the problem in some developed countries, nitrate pollution is still on the rise in many other countries. Innovative, low-cost biological denitrification processes are specially needed in developing countries.     

Biodegradation combined with ozone for the remediation of contaminated soils

The effectiveness of the SS-SBR (Soil Slurry – Sequencing Batch Reactor) process for the remediation of soils contaminated by several organic pollutants has been evaluated. Experimental tests have been performed on two different soils, a spiked one and an industrial aged soil. The spiked soil, artificially contaminated, has been prepared trying to simulate the pollution of an industrial aged soil in terms of number and kind of contaminants. PAHs (Polycyclic Aromatic Hydrocarbons) and phenols degradation has been particularly investigated because they are considered persistent and recalcitrant. Concerning the spiked soil, removal efficiencies higher than 95% in 6 to 9 weeks have been found for all the pollutants, except for five-rings PAHs; however, these compounds were partly removed in 11 to 13 weeks. Good results have been achieved also for the industrial aged soil with a maximum removal of about 80% in 7–8 weeks. To enhance the pollutants degradation, trying to obtain a faster remediation, the biological treatment has been combined with a chemical oxidation with ozone. The best degradation effectiveness of the combined process has been obtained applying the ozonation after few days of the biological treatment. Therefore, a combined biological and chemical treatment allowed to markedly improve the remediation of contaminated soils.