Pharmaceutical wastewater degradation: effective and economical treatment using waste-metallic iron shavings

Industrial wastewater generated by a drug manufacturing plant located in Spain was degraded by Fenton oxidation processes, which employ waste-metallic iron shavings as heterogeneous zero-valent iron (ZVI) catalyst and hydrogen peroxide. The effluent comprises a complex mixture of organic substances which are very refractory to common conventional treatments and it is characterized by a low BOD/COD ratio. The stirring speed or the particle size has been found to be the determining factors, greatly influencing the degradation of the organic pollutants present in the wastewater. The influence of the initial hydrogen peroxide concentration has also been evaluated. The optimal conditions for degradation led to total organic carbon (TOC) reductions of up to 60%. The remarkable results of TOC mineralization could also be attributed to the physico-chemical modification of the ZVI during the oxidizing process. This study shows that the ZVI/H₂O₂ system can be considered as an easy, economic and effective alternative solution as a pre-treatment step before biological treatments.     

Optimization of hydroxyl radical production using electro‐Fenton method for chemical oxygen demand reduction in diluted palm oil mill effluent

Palm oil mill effluent (POME) is a well‐known highly polluting wastewater due to its extremely high contents of organic matter, suspended solids and nutrients. In this study, we used electro‐Fenton method to treat POME by optimizing OH? generation from hydrogen peroxide (H₂O₂) under low voltage input (1.5–6.0 V). A set of electro‐Fenton system was set up using stainless steel as the anode and graphite as the cathode. Four parameters namely retention times, concentrations of H₂O₂ as well as FeSO₄ catalyst and applied voltages were studied. The results were reflected in the form of removal efficiency of chemical oxygen demand (COD). The optimum conditions to degrade organic matter in POME were found to be in 4 h retention time with the respective H₂O₂ and FeSO₄ catalyst concentrations of 0.05 and 0.10 M, and the power input of 1.5 V. Under such conditions, the maximum COD removal efficiency achieved 94%. The electro‐Fenton treatment was found to have higher efficiency than the conventional Fenton treatment. Without the electrolysis, the COD removal efficiency of the conventional Fenton treatment was only 48%.     

Photocatalytic destruction of anionic SAS with oxygen and hydrogen peroxide in the TiO2 suspension

The articles gives a comparison of the rates and the degree of destruction of anionic SAS-alkyl benzene sodium sulfonate (ABS) in heterogeneous (O₂/TiO₂/UV, H₂O₂/TiO₂/UV) and homogeneous (O₂/UV, H₂O₂/UV) oxidizing systems on several TiO₂ samples at UV irradiation by a SVD-120 high-pressure mercury-quartz lamp. The paper has demonstrated a possibility of achieving a high degree of photocatalytic destruction of ABS by hydrogen peroxide (100, 90, and 80% respectively by the ABS concentration of ABS, COD, and TOC over two hours).     

A mercury-free accelerated method for determining the chemical oxygen demand of large numbers of water samples by autoclaving them under pressure with acid-dichromate

In order to fulfill the objective of a water control program based on frequent sampling in several wastewater treatment plants, rivers and lakes a simplified method for measuring COD was developed. The procedure, in this article called the RR-method, includes: small sample and reagent volume; rapid addition of a mixture of all reagents to the sample; exclusion of mercury; autoclaving at 120°C for 1 h in flasks with fitted glass stoppers. To avoid dilution before analysis the method has been adapted for wastewater (I: 10–300 mg O₂ l⁻¹) and fresh water (II: 10–100 mg O₂ l⁻¹).Parallel analyses on different types of water samples according to Standard Methods showed that the yield by the RR-method was about 10% lower (Table 2). With water from the wastewater treatment plant at Uppsala (COD around 20 mg O₂ l⁻¹), the two methods gave an identical result. The somewhat lower yield was mostly due to decreased dichromate concentration and oxidation temperature. The lower oxidation potential made correction for chloride interference unnecessary below 1 g Cl⁻ l⁻¹ (Table 1).The RR-method also showed a good correlation to the values for KMnO₄-consumption. Parallel analyses of 318 samples from 14 wastewater receiving lakes gave the correlation coefficient r = +0.90 (Fig. 1).     

The elimination of sulfur dioxide interference in the low level chemical oxygen demand analysis

Sulfur dioxide is a reduced compound which acts as a positive interference in the chemical oxygen demand (COD) analysis. Significant amounts of sulfur dioxide present in industrial waste samples may therefore result in erroneously high COD values, compared to that of a sample with only the organic portion of the waste. By adding 65 mg l⁻¹ Mn²⁺ to a secondary wastewater sample spiked with 500 mg l⁻¹ sulfur dioxide, and oxygenating the sample for 6 min, sulfur dioxide was oxidized completely to sulfate. This oxidation procedure provides a statistically valid means of removing SO₂ interference in the COD analysis. The procedure provides an efficient means of investigating the organic COD of industrial effluents laden with SO₂ or its dissociation products.     

Synergetic pretreatment of sewage sludge by microwave irradiation in presence of H2O2 for enhanced anaerobic digestion

A microwave-enhanced advanced hydrogen peroxide oxidation process (MW/H₂O₂-AOP) was studied in order to investigate the synergetic effects of MW irradiation on H₂O₂ treated waste activated sludges (WAS) in terms of mineralization (permanent stabilization), sludge disintegration/solubilization, and subsequent anaerobic biodegradation as well as dewaterability after digestion. Thickened WAS sample pretreated with 1 g H₂O₂/g total solids (TS) lost 11-34% of its TS, total chemical oxygen demand (COD) and total biopolymers (humic acids, proteins and sugars) via advanced oxidation. In a temperature range of 60-120 °C, elevated MW temperatures (>80 °C) further increased the decomposition of H₂O₂ into OH^• radicals and enhanced both oxidation of COD and solubilization of particulate COD (>0.45 micron) of WAS indicating that a synergetic effect was observed when both H₂O₂ and MW treatments were combined. However, at all temperatures tested, MW/H₂O₂ treated samples had lower first-order mesophilic (33 ± 2 °C) biodegradation rate constants and ultimate (after 32 days of digestion) methane yields (mL per gram sample) compared to control and MW irradiated WAS samples, indicating that synergistically (MW/H₂O₂-AOP) generated soluble organics were slower to biodegrade or more refractory than those generated during MW irradiation.     

Assessment of the UV/chlorine process as an advanced oxidation process

Several organic compounds were used as radical scavengers/reagents to investigate the possibility of the UV/chlorine process being used as an advanced oxidation process (AOP) in the treatment of drinking water and wastewater. The UV/H₂O₂ process was selected as a reference, so that the results from the UV/chlorine process could be compared with those of the UV/H₂O₂ process. Methanol was added to active chlorine solutions at both pH 5 and 10 and into hydrogen peroxide samples. The photodegradation quantum yields and the OH radical production yield factors, which are significant in evaluating AOPs, were calculated for both the UV/chlorine and the UV/H₂O₂ processes. The yield factor for the UV/chlorine process at pH 5 was 0.46 ± 0.09, which is much lower than that of the UV/H₂O₂ process, which reached 0.85 ± 0.04. In addition to methanol, para-chlorobenzoic acid (pCBA) and cyclohexanoic acid (CHA) were added to active chlorine solutions and to H₂O₂ solutions, to evaluate the efficiencies of oxidizing these organic compounds. The specific first-order reaction rate constants for the oxidation of pCBA and CHA, using the UV/chlorine process, were lower than those found using the UV/H₂O₂ process.     

Photocatalytic Destruction of Fulvic Acids by Various Oxidants in a Reactor with Immobilized TiO<Subscript>2</Subscript>

Comparison of the efficiency of photocatalytic oxidation of aqueous solution of fulvic acids (TOC₀—15.9–17.1 mg/dm³, pH0 6 ± 0.1) by oxygen of the air, hydrogen peroxide and ozone in a reactor containing a wide-porous ceramic block with immobilized TiO₂ with the variation of the concentration of H₂O₂, feed rate of O₃ and temperature showed advantages of photocatalytic ozonization and expediency of its use for deep destruction of natural organic substances in water. The maximum degree of destruction in photocatalytic systems O₂/TiO₂/UV, H₂O₂/TiO₂/UV and O₃/TiO₂/UV constituted respectively 41, 73 and 90% for TOC for 5, 4 and 3 h.     

Evaluation of UV/H2O2 treatment for the oxidation of pharmaceuticals in wastewater

Advanced oxidation treatment using low pressure UV light coupled with hydrogen peroxide (UV/H₂O₂) was evaluated for the oxidation of six pharmaceuticals in three wastewater effluents. The removal of these six pharmaceuticals (meprobamate, carbamazepine, dilantin, atenolol, primidone and trimethoprim) varied between no observed removal and >90%. The role of the water quality (i.e., alkalinity, nitrite, and specifically effluent organic matter (EfOM)) on hydroxyl radical (OH) exposure was evaluated and used to explain the differences in pharmaceutical removal between the three wastewaters. Results indicated that the efficacy of UV/H₂O₂ treatment for the removal of pharmaceuticals from wastewater was a function of not only the concentration of EfOM but also its inherent reactivity towards OH. The removal of pharmaceuticals also correlated with reductions in ultraviolet absorbance at 254 nm (UV₂₅₄), which offers utilities a surrogate to assess pharmaceutical removal efficiency during UV/H₂O₂ treatment.     

The use of hydrogen peroxide for raising the efficiency of filter operation with biologically activated carbon

We have investigated the impact of hydrogen peroxide on the efficiency of biofiltration of the solutions of fulvic acids through biologically activated carbon with a native biofilm. We have also determined optimal conditions for using hydrogen peroxide in the processes of filtration through carbon. The use of H₂O₂ at the concentration 5 mg/dm³ is the most expedient since it makes it possible to enrich a solution of natural organic matter, in particular, fulvic acids with oxygen. It has been demonstrated that oxygen released during catalytic decomposition of H₂O₂ is actively consumed by microorganisms in the filter medium.     

Lethal synergy of solar UV-radiation and H2O2 on wild Fusarium solani spores in distilled and natural well water

Environmentally-friendly disinfection methods are needed in many industrial applications. As a natural metabolite of many organisms, hydrogen peroxide (H₂O₂)-based disinfection may be such a method as long as H₂O₂ is used in non-toxic concentrations. Nevertheless, when applied alone as a disinfectant, H₂O₂ concentrations need to be high enough to achieve significant pathogen reduction, and this may lead to phytotoxicity. This paper shows how H₂O₂ disinfection concentrations could be significantly reduced by using the synergic lethality of H₂O₂ and sunlight the first time for fungi and disinfection. Experiments were performed on spores of Fusarium solani, the ubiquitous, pytho- and human pathogenic fungus. Laboratory (250-mL bottles) and pilot plant solar reactors (2 × 14 L compound parabolic collectors, CPCs) were employed with distilled water and real well water under natural sunlight. This opens the way to applications for agricultural water resources, seed disinfection, curing of fungal skin infections, etc.     

Photooxidative destruction of organic compounds by hydrogen peroxide in water

The paper has studied the state of the art in the investigations into the kinetics and the mechanism of photoinduced oxidative destruction of organic compounds of various classes by hydrogen peroxide in aqueous media. We have analyzed the impact of physical and chemical factors (substrate structure, pH of the medium, H₂O₂ concentration, presence of oxygen, etc.) and the rate of the photooxidative process. The analysis of the technicoeconomic characteristics of the UV/H₂O₂ system in correlation with other highly effective AOP methods (Advanced Oxidation Processes) is an evidence of good prospects of using it in the technology of treating natural and industrial wastewaters from organic pollutants.     

Formation and decomposition of hydrogen peroxide during UV-radiation,ozonization, and O<Subscript>3</Subscript>/UV treatment of river water

We have studied the kinetics of the formation of hydrogen peroxide during UV-radiation, ozonization, and O₃/UV treatment of water of the Dnieper River and model solutions of fulvic acids. We have also investigated decomposition of added hydrogen peroxide at the indicated methods of treating river and model waters and the impact of H₂O₂ on the concentration of dissolved ozone.     

Comparison of UV-Cl and UV-H2O2 advanced oxidation processes in the degradation of contaminants from water and wastewater: A review

Applications of advanced oxidation processes (AOPs) in water and wastewater treatment have been the subject of growing interest throughout the last decade. Although UV/hydrogen peroxide (UV-H₂O₂) is the most established technology among the UV-AOPs, UV-chlorine (UV-Cl) is emerging as a reliable and potentially more cost-effective alternative. Recent studies have indicated that UV-Cl processes may be more efficient and economically favourable for the degradation of some chemicals of emerging concern from contaminated water. Moreover, in terms of the formation of disinfection by-products (DBPs), UV-H₂O₂ seems to have no superiority over UV-Cl. This said, more investigation in the assessment of genotoxicity and cytotoxicity of DBPs is required. Additionally, more pilot-scale and full-scale studies are required to establish UV-Cl as a reliable alternative to UV- H₂O₂. This paper compares UV-Cl and UV-H₂O₂ AOPs for the degradation of intractable chemicals from water and wastewater based on the practical considerations of efficiency, cost, DBP formation, kinetics and sensitivity to water matrix variability. Finally, various modelling approaches to UV-Cl have been reviewed. This review showed that UV-Cl is superior to UV-H₂O₂ in terms of degradation efficiency and cost effectiveness and can be a robust alternative in many UV-AOPs applications.     

Greywater treatment by UVC/H2O2

Greywater treatment by UVC/H₂O₂ was investigated with regard to the removal of chemical oxygen demand (COD). A COD reduction from 225 to 30 mg l⁻¹ (overall removal of 87%) was achieved after settling overnight and subsequent irradiation for 3 h with 10 mM H₂O₂. Most of the contaminants were removed by oxidation since only 13% COD was removed by settlement.The removal of COD in the greywater followed a second-order kinetic equation, r = 0.0637[COD][H₂O₂], up to 10 mM H₂O₂. A slightly enhanced COD removal was observed at the initial pH of 10 compared with pH 3 and 7. This was attributed to the dissociation of H₂O₂ to O₂H⁻. The treatment was not affected by total concentration of carbonate (c_T) of at least 3 mM, above which operation between pH 3 and 5 was essential. The initial biodegradability of the settled greywater (as BOD₅:COD) was 0.22. After 2 h UVC/H₂O₂ treatment, a higher proportion of the residual contaminants was biodegradable (BOD₅:COD = 0.41) which indicated its potential as a pre-treatment for a biological process.     

Treatment of high strength hexamine-containing wastewater by electro-Fenton method

A novel Electro-Fenton (EF–Fere) method, applied H₂O₂ and electrogenerated ferrous ion, was investigated for treating the hexamine-containing wastewater. The performance of Fe²⁺ generation in the electrolytic system was first evaluated, including the factors of the cathode material, initial pH, initial ferric concentration (Fe_i), and current density. When initial pH exceeded 2.5, the current efficiency dramatically decreased, which was due to the formation of Fe(OH)₃. Between 3000 and 10,000 mg/l of Fe_i, the initial current efficiency of Fe²⁺ generation was almost constant (85–87%), which dropped sharply to 39% at 1000 mg/l. In EF–Fere experiments, the COD removal efficiency attained above 94% after 5 h of reaction. The relationship between the temperature, dissolved oxygen, and COD was discussed. The changes in hexamine and its oxidation intermediates (methanol, formaldahyde, formate, ammonium and nitrate) during the reaction were also investigated. Three additional experiments using H₂O₂/Fe²⁺, H₂O₂/Fe³⁺, and direct electrolysis were also conducted to treat the hexamine-containing wastewater for comparison. The results showed that the EF–Fere method was the most efficient.     

Photodegradation of phenol red in the presence of oxyhydroxide of Fe(III) (Goethite) under artificial and a natural light

The (α‐FeOOH) Goethite composite is a stable and an efficient catalyst in aqueous suspension under irradiation at 365 nm and by solar light. The photocatalytic activities of this composite were evaluated using Phenol Red (PR) dye (phenolsulfonphthalein class). In the dark, controlling factors, such as the pH and the adsorption of PR on Goethite surface were evaluated (before starting the photochemical experiments). It was found that the system PR‐Goethite present a small decrease in the main band of the dye (435 nm) which was explained by the low rate of adsorption of this dye on the Goethite. Also, we note that 40% of PR decolourisation was obtained after 200 min by the system PR‐Goethite‐hydrogen peroxide (H₂O₂) in dark due to the formation of ^?OH by thermal decomposition of H₂O₂ on the surface of Goethite. The effects of various experimental parameters, such as initial dye concentration, pH, photocatalyst amount, tert‐Butyl alcohol effect and H₂O₂ addition were investigated in the study of photodegradation of the dye. The results showed that the photodegradation of PR under UV‐A (365 nm) irradiation could be enhanced greatly in the presence of H₂O₂. Natural radiation tests (under sunlight) showed that degradation was faster comparing with that obtained using the artificial one at 365 nm. Studies of the mineralization using total organic carbon method under naturel light certify that this method, compatible with the environment, may be considered in the treatment of wastewater and generally in the process of removal of this kind of pollutant.     

Selective suppression of harmful cyanobacteria in an entire lake with hydrogen peroxide

Although harmful cyanobacteria form a major threat to water quality, few methods exist for the rapid suppression of cyanobacterial blooms. Since laboratory studies indicated that cyanobacteria are more sensitive to hydrogen peroxide (H₂O₂) than eukaryotic phytoplankton, we tested the application of H₂O₂ in natural waters. First, we exposed water samples from a recreational lake dominated by the toxic cyanobacterium Planktothrix agardhii to dilute H₂O₂. This reduced the photosynthetic vitality by more than 70% within a few hours. Next, we installed experimental enclosures in the lake, which revealed that H₂O₂ selectively killed the cyanobacteria without major impacts on eukaryotic phytoplankton, zooplankton, or macrofauna. Based on these tests, we introduced 2 mg L⁻¹ (60 μM) of H₂O₂ homogeneously into the entire water volume of the lake with a special dispersal device, called the water harrow. The cyanobacterial population as well as the microcystin concentration collapsed by 99% within a few days. Eukaryotic phytoplankton (including green algae, cryptophytes, chrysophytes and diatoms), zooplankton and macrofauna remained largely unaffected. Following the treatment, cyanobacterial abundances remained low for 7 weeks. Based on these results, we propose the use of dilute H₂O₂ for the selective elimination of harmful cyanobacteria from recreational lakes and drinking water reservoirs, especially when immediate action is urgent and/or cyanobacterial control by reduction of eutrophication is currently not feasible. A key advantage of this method is that the added H₂O₂ degrades to water and oxygen within a few days, and thus leaves no long-term chemical traces in the environment.     

Anaerobic treatment of brewary wastewater with simultaneous hydrogen production

Processes of brewery wastewater treatment with sequential use of the fermentative and bioelectrochemical methods have been investigated. A two-stage fermentation increases the rate of substrate utilization and hydrogen production. The water treatment efficiency in terms of COD in the first and second fermenters amounts to 55–65% and 65–72%, respectively. The hydrogen concentration in biogas can reach 65%. The organic acids produced in anaerobic fermentation process represent a substrate for exoelectrogenic microorganisms of bioelectrochemical fuel cell, where the secondary wastewater treatment takes place for achieving COD values of 200–400 mg/dm³. The combination of the fermentative and bioelectrochemical processes of hydrogen production makes it possible to increase its yield by a factor of 2–4 and reach the level of 7–9 moles of H₂ per 1 mole of glucose.     

Hydrogen peroxide as a potential algicide for oscillatoria rubescens D.C.

The algicidal properties of hydrogen peroxide (H₂O₂) for Oscillatoria rubescens were evaluated at different concentrations between 0 and 7 ppm. The toxicity threshold, under laboratory conditions, was about 1.75 ppm depending on culture density. Higher concentrations of H₂O₂ destroyed more than 90% of biliproteins and carotenoids and nearly 50% of chlorophyll, whereas they had no noticeable effect on Pandorina morum, a chlorophyte tested for comparison. This differential sensitivity is discussed on the basis of chemical and physical pigment fragility. Mixed continuous culture experiments suggest a possible shift from blue-greens to volvocales following the use of H₂O₂ as an algicide.