Ozone-driven processes for mature urban landfill leachate treatment: Organic matter degradation, biodegradability enhancement and treatment costs for different reactors configuration

Destabilization mechanisms of Semi-aerobic aged refuse biofilters under harsh treatment conditions: Evidence from fluorescence and microbial characteristics

Semi-aerobic aged refuse biofilters (SAARB) are commonly-used biotechnologies for treating landfill leachate. In actual operation, SAARB often faces harsh conditions characterized by high concentrations of chemical oxygen demand (COD) and Cl-, as well as a low carbon-to-nitrogen ratio (C/N), which can disrupt the microbial community within SAARB, leading to operational instability. Maintaining the stable operation of SAARB is crucial for the efficient treatment of landfill leachate. However, the destabilization mechanism of SAARB under harsh conditions remains unclear. To address this, the study simulated the operation of SAARB under three harsh conditions, namely, high COD loading (H-COD), high chloride ion (Cl-) concentration environment (H-Cl-), and low C/N ratio environment (L-C/N). The aim is to reveal the destabilization mechanism of SAARB under harsh conditions by analyzing the fluorescence characteristics of effluent DOM and the microbial community in aged refuse. The results indicate that three harsh conditions have different effects on SAARB. H-COD leads to the accumulation of proteins; H-Cl- impedes the reduction of nitrite nitrogen; L-C/N inhibits the degradation of humic substances. These outcomes are attributed to the specific effects of different factors on the microbial communities in different zones of SAARB. H-COD and L-C/N mainly affect the degradation of organic matter in aerobic zone, while H-Cl- primarily impedes the denitrification process in the anaerobic zone. The abnormal enrichment of Corynebacterium, Castellaniella, and Sporosarcina can indicate the instability of SAARB under three harsh conditions, respectively. To maintain the steady operation of SAARB, targeted acclimation of the microbial community in SAARB should be carried out to cope with potentially harsh operating conditions. Besides, timely mitigation of loads should be implemented when instability characteristics emerge, and carbon sources and electron donors should be provided to restore treatment performance effectively.

Leachate management in medium- and small-sized sanitary landfills: a Greek case study

The sustainable management of landfill leachates remains a matter of important concern in many countries. We used as case study a medium-sized Greek landfill, and we initially investigated the performance of the existing secondary leachate treatment system. The activated sludge process removed chemical oxygen demand (COD), biochemical oxygen demand (BOD), NH4-N, and PO4-P by 55%, 84%, 94%, and 14%, respectively, but the effluents did not meet the legislation requirements for discharge or reuse. Afterwards, different management options of these effluents (co-treatment with sewage in the centralized treatment plant, onsite tertiary treatment with reverse osmosis, granular activated carbon (GAC), ozonation, photo-Fenton, or constructed wetlands) were evaluated regarding their operational costs and environmental footprint. The use of constructed wetlands presented the lower operational cost, energy requirements, and greenhouse gas (GHG) emissions, not exceeding 21.5 kg CO2eq/day. On the other hand, the power consumption and the GHG emissions of the other on-site technologies ranged from 0.37 kWh/m3 and 5.56 kg CO2eq/day (use of GAC) to 39.19 kWh/m3 and 588.6 kg CO2eq/day (use of ozonation), respectively. The co-treatment of the leachates with municipal wastewater required 0.6 kWh/m3 and emitted 30.18 kg CO2eq/day. For achieving zero-discharge of the treated leachates, a system consisting of constructed wetlands and evaporation ponds in series was designed.

Coagulation and ozonation treatment of biologically treated wastewater from recycled paper pulping industry: effect on the change of organic compounds

Recycled paper pulping wastewater (RPPW) will cause serious environmental problems due to the high loads of dissolved organic matter (DOM) and toxic components. In the present work, the degradation of DOM in the biologically treated RPPWs (cardboard wastewater (CW) and corrugated container wastewater (CCW)) by a combined coagulation and ozonation process was investigated. The optimal chemical oxygen demand (COD) removal of CW reached 73.64% at aluminum sulfate (Al2(SO4)3) dosage of 800 mg/l, aeration aperture of 10 μm, pH of 9, hydrogen peroxide (H2O2) dosage of 100 mg/l, and reaction time of 70 min. The optimal COD removal of CCW reached 55.76% at a poly-aluminum chloride (PAC) dosage of 700 mg/l, H2O2 dosage of 140 mg/l, and reaction time of 50 min. This study provided some insights into the change of DOM during the combined treatment through the use of UV-Vis spectroscopy and excitation-emission matrix spectroscopy (EEM). PAC and Al2(SO4)3 removed high molecular weight organic such as lignin and lignin-derived compounds to improve the biodegradability of the wastewater. Ozone oxidized high molecular weight organic with complex functional groups to low molecular weight organic with simple functional groups and even mineralization, and this phenomenon resulted in the COD of ozonation effluent significantly reduced. Thus, the results presented in this study support the application of the combined coagulation and ozonation process in treating RPPW.

Enhanced performance and mechanism of the combined process of ozonation and a semiaerobic aged refuse biofilter for mature landfill leachate treatment

A semiaerobic aged refuse biofilter (SAARB) can effectively treat mature landfill leachate (ML), but prolonged operation can lead to the enrichment of pollutants in the biofilter, resulting in severely degraded treatment performance. In this study, we constructed a combination process of ozonation and a SAARB to treat ML based on the principles of selective oxidation of aromatic organics by ozone and the preference of microorganisms for ozonation products. The results showed that the removal of organic and nitrogen pollutants became extremely poor after long-term treatment of ML using the SAARB alone. The decrease of chemical oxygen demand (COD), light absorbance at 254 nm (UV₂₅₄), NH₄⁺, and total nitrogen (TN) improved significantly after recirculating the ozonated ML effluent (OLE) into the SAARB, and the removal extents increased significantly to 63.59% (COD), 26.14% (UV₂₅₄), 92.85% (NH₄⁺), and 52.04% (TN), respectively. In addition, the recirculation of OLE enhanced the complete denitrification and tolerance to high NH₄⁺ loading by the SAARB. An analysis of the community composition of 16S_bacteria and ammonia oxidation bacteria (AOB) showed that long-term treatment of ML using the SAARB alone had difficulty enriching the dominant functional bacteria. In the OLE recirculation stage, environmental factors-such as influent organic matter species and concentration, nitrogen pollutant concentration, and pH-were changed to influence the community composition of 16S_bacteria and AOB and enrich functional bacteria (e.g., Truepera, Luteibacter, and Nitrosospira). Therefore, ozonation combined with a SAARB can remove organic and nitrogen pollutants more effectively. In particular, this can be used to solve the problem of inefficient total nitrogen removal using the SAARB alone. This study provides a theoretical reference for the efficient and stable operation of biological processes when treating ML.

Hydrogen peroxide and peroxymonosulfate intensifying Fe-doped NiC-Al2O3-framework-based catalytic ozonation for advanced treatment of landfill leachate: Performance and mechanisms

The biotreated effluent of landfill leachate still contains numerous refractory organic contaminants, which poses potential threats to human health and ecosystems. Influenced by landfill ages and other factors, the concentration of organic matter varies. Heterogeneous catalytic ozonation (HCO) is a promising technology for advanced wastewater treatment. Aiming to achieve the up-to-standard discharge of low-concentration landfill leachate (COD ≈ 108 mg·L^-1) and improve the biodegradability of high-concentration landfill leachate (COD ≈ 1720 mg·L^-1), the active component Fe was incorporated into a firm Ni-induced C-Al₂O₃-framework (_NiCAF) composite support to synthesize a Fe-_NiCAF catalyst for efficient catalytic ozonation. When the Fe-_NiCAF dosage was 4 g·L^-1, the gas flow rate was 0.5 L·min^-1, and the ozone concentration was 20.0 mg·L^-1, the COD of low-concentration landfill leachate effluent decreased to 43 mg·L^-1, and the COD removal rate constant of low-concentration landfill leachate was 154% higher than that of pure ozone. For high-concentration landfill leachate with the BOD₅/COD of 0.058, the COD removal efficiency in Fe-_NiCAF/O₃ increased from 39% to 57% compared with ozonation, and the effluent BOD₅/COD increased to 0.282. Furthermore, the addition of hydrogen peroxide (H₂O₂) and peroxymonosulfate (PMS) can further enhance the treatment performance of Fe-_NiCAF/O₃ process and different strengthening mechanisms were revealed. The results indicated that surface hydroxyls on the Fe-_NiCAF catalyst surface were the main catalytic sites for ozone, and hydroxyl radical (•OH) and singlet oxygen (¹O₂) were identified as the main reactive oxygen species for the removal of organics in landfill leachate. Adding H₂O₂ can promote the generation of •OH for nonselective degradation of various organics, while PMS mainly enhanced the production of ¹O₂ to decompose macromolecular humus. This work highlighted an efficient Fe-_NiCAF ozone catalyst and an innovative peroxide intensified HCO strategy for the advanced treatment of landfill leachate.

Mitigation of inhibitory effect of THP-AD centrate on partial nitritation and anammox: Insights into ozone pretreatment

Anaerobic digestion centrate produced from thermal hydrolysis pretreated sludge (THP-AD centrate) has serious inhibitory effect on ammonium oxidizing bacteria (AOB) and anammox bacteria. This imposes huge challenge to employ partial nitritation/anammox (PN/A) process to treat THP-AD centrate. This study, for the first time, presented an effective strategy, ozone pretreatment, to alleviate such inhibitory effect. The activities of AOB and anammox bacteria increased with increasing ozone dosage, which were likely related to the transformation of organic compounds including humic acid-like and fulvic acid-like substances as well as high molecular weight (HMW) protein. Long-term operation of PN/A system further demonstrated the improved performance in term of nitrogen removal, organics degradation as well as sludge settleability and effluent solids. Nitrogen removal rate (NRR) of 0.64 Kg N/m³/d was achieved (1.38 g O₃/ g COD), which was 42.2% higher compared to treating untreated THP-AD centrate. Effluent nitrate, the by-product of PN/A process, was reduced by 39.7% despite of its release in ozonation. This was due to the enhanced denitrification activity, humic acid-like and fulvic acid-like substances as well as HMW protein were significantly reduced. Overall, this study provides a promising method to improve PN/A performance and final effluent quality when treating organic-rich THP-AD centrate.

A tubular ceramic membrane coated with TiO2-P25 for radial addition of H2O2 towards AMX removal from synthetic solutions and secondary urban wastewater

This work aims to integrate several hydrogen peroxide (H₂O₂) activation mechanisms, photolysis (UVC irradiation), chemical electron transfer (TiO₂-P25 photocatalysis), and reaction with TiO₂-P25 in dark conditions, for reactive oxygen species (ROS) generation towards the removal of contaminants of emerging concern (CECs), in a single unit operated in continuous-flow mode. An H₂O₂ stock solution is fed by the lumen side of a tubular ceramic membrane, delivering the oxidant to the (i) catalyst immobilized in the membrane shell-side and (ii) annular reaction zone (ARZ, space between membrane shell-side and outer quartz tube) where CECs contaminated water flows with a helix trajectory, being activated by UV light provided by four lamps placed symmetrically around the reactor. First, the effect of several parameters in the removal of a CEC target molecule, amoxicillin (AMX), was evaluated using a synthetic solution ([AMX]_inlet = 2.0 mg L^-1): (i) light source (UVA or UVC radiation), (ii) H₂O₂ dose, (iii) H₂O₂ injection method (radial permeation vs. upstream injection), and (iv) number of TiO₂-P25 layers deposited on the membrane. The UVC/H₂O₂/TiO₂ system with radial addition of H₂O₂ (20 mg L^-1) and 9-TiO₂-P25 layers provided the highest AMX removal efficiency (72.2 ± 0.5%) with a UV fluence of 45 mJ cm^-2 (residence time of 4.6 s), due to the synergic effect of four mechanisms: (i) AMX photolysis, (ii) H₂O₂ photocleavage, (iii) TiO₂-P25 photoactivation, and (iv) chemical reactions between H₂O₂ and TiO₂-P25. The urban wastewater matrix showed a negative effect on AMX removal (~44%) due to the presence of ROS scavengers and light-filtering species.

Advanced oxidation process based on hydroxyl and sulfate radicals to degrade refractory organic pollutants in landfill leachate

As a special type of wastewater produced in the landfill, leachate is mainly composed of organic pollutants, inorganic salts, ammonia nitrogen and heavy metals, and featured by high pollutants concentration, complex composition and large fluctuations in water quality and volume. Biological, chemical and physical methods have been proposed to treat landfill leachate, but much attention has been paid to the advanced oxidation processes (AOPs), due to their high adaptability and organic degradation efficiency. This paper summarizes the recent findings on the AOPs based on hydroxyl radical (OH) (e.g., ozonation and catalyzed ozone oxidations, Fenton and Fenton-like oxidations) and sulfate radical (SO₄^-) (e.g., activated and catalyzed persulfate oxidations), especially the production routes of free radicals and mechanisms of action. When dealing with some special landfill leachates, it is difficult for a single advanced oxidation technology to achieve the expected results, but the synergistic combination with biological or physical methods can produce satisfactory outcomes. Therefore, this paper has summarized the application of these combined treatment technologies on landfill leachate.

Advanced treatment of landfill leachate through combined Anammox-based biotreatment, O3/H2O2 oxidation, and activated carbon adsorption: technical performance, surrogate-based control strategy, and operational cost analysis

The complexity of landfill leachate makes it difficult to treat it with a single biological/ physical/chemical process. Moreover, the dynamic leachate characteristics pose a challenge for effective process control. Therefore, a combined treatment, consisting of a one-stage partial nitrification-Anammox process, an O₃/H₂O₂ process, and a granular activated carbon filtration (GAC) process, was investigated. Meanwhile, a novel surrogate-based ozone dose control strategy for O₃/H₂O₂ process was evaluated. Results show that this three-stage process offers high removal of total nitrogen (> 90%), COD (chemical oxygen demand, 60-82%), and micropollutants (atrazine, alachlor, carbamazepine, and bisphenol A, > 96%), satisfying discharge requirements. In the combined post-treatment, ozone dosing for COD removal can be real-time controlled by UVA₂₅₄ reduction monitoring, based on a specific correlation between COD and UVA₂₅₄ changes. On the other hand, O₃/H₂O₂ pre-treatment controlled at a 50% UVA₂₅₄ reduction shows to be the optimal point, when adsorption is designed as the main step for COD removal. Cost analysis shows that post-treatment with low (high) organic load i.e., COD ≤ (≥)540 mg/L, a combination with O₃/H₂O₂ (GAC) as the main step appears to be more cost-effective. Therefore, a dynamic operation strategy in response to the leachate change is recommended.

Optimization of ozonation process for organic matter and ecotoxicity removal from landfill leachate by applying rotatable central composite design (RCCD)

Ozonation process was used for leachate treatment from a landfill located in Rio de Janeiro, Brazil. The influence of pH and ozone concentration on COD (Chemical Oxygen Demand), TOC (Total Organic Carbon), Absorbance at 254 nm (ABS254nm), and True color was evaluated through RCCD (Rotatable Central Composite Design) experimental design, resulting in mathematical models that were statistically analyzed in Statistica and Design Expert software. The removals obtained was up to 26.1%, 29.9%, 56.9%, and 97.9% for COD ([COD]₀=3,323 mg/L), TOC ([TOC]₀=1,275 mg/L), ABS254nm (ABS₀=32.2), and True color ([True color]₀=3,467 mgPt-Co/L), respectively. Statistical and variance analysis of the experimental data revealed that one quadratic model obtained in Statistica was valid, ABS254nm reduction. However, by applying the Design Expert software, modified models were generated to predict the behavior of all dependent variables. Thus, the optimum point for the best response after ozonation of the landfill leachate was at the highest pH and the lowest ozone dose (9 and 2.2 mgO₃/m³, respectively). Toxicity toward Allivibrio fischeri bacteria was abated at the same time that it decreased the impact of the effluent to Danio rerio fish (from 125 UT to 62 UT) on the treated leachate.

How does the pre-treatment of landfill leachate impact the performance of O3 and O3/UVC processes?

In this study, O₃ and O₃/UVC processes were evaluated for the treatment of landfill leachate after biological nitrification/denitrification, coagulation, or their combinations. The O₃-driven stage efficiency was assessed by the removal of color, organic matter (dissolved organic carbon (DOC) and chemical oxygen demand (COD)), and biodegradability increase (Zahn-Wellens test). Also, fluorescence excitation-emission matrix (EEM) and size exclusion chromatography coupled with OC detector (SEC-OCD) analysis were carried out for each strategy. The bio-nitrified-leachate (L_N) was not efficiently mineralized during the O₃-driven processes since the high nitrites content consumed ozone rapidly. In turn, carbonate/bicarbonate ions impaired the oxidation of the bio-denitrified-leachate (L_D), scavenging hydroxyl radicals (HO^•) and inhibiting the O₃ decomposition. For both bio-leachates, only O₃/UVC significantly enhanced the effluent biodegradability (>70%), but COD legal compliance was not reached. EEM and SEC-OCD results revealed differences in the organic matter composition between the nitrified-coagulated-leachate (L_NC) and denitrified-coagulated-leachate (L_DC). Nonetheless, the amount of DOC and COD removed per gram of ozone was similar for both. Cost estimation indicates the O₃-driven stage as the costliest among the treatment processes, while coagulation substantially reduced the cost of the following ozonation. Thus, the best treatment train strategy comprised L_DC (with methanol addition for denitrification and coagulated with 300 mg Al³⁺/L, without pH adjustment), followed by O₃/UVC (transferred ozone dose of 2.1 g O₃/L and 12.2 kJ_UVC/L) and final biological oxidation, allowed legal compliance for direct discharge (for organic and nitrogen parameters) with an estimated cost of 8.9 €/m³ (O₃/UVC stage counting for 6.9 €/m³).

A microwave radiation-enhanced Fe-C/persulfate system for the treatment of refractory organic matter from biologically treated landfill leachate

In this study, a microwave (MW) radiation enhanced Fe-C/PS system was used to treat refractory organic matter in biologically-treated landfill leachate. The effects of important influencing factors on the refractory organic matter in biologically treated landfill leachate were explored, and the main reactive oxygen species produced in the system were verified. The mechanism by which humus was degraded was investigated by analyzing effectiveness of organics removal in different systems, and comparative analysis was conducted on the Fe-C materials before and after the reaction. The results showed that degradation capacity and reaction rate of the system could be improved with an increase in the Fe-C/PS dosage and MW power, while initial acidic conditions were also conducive to the degradation of organic matter. Under the conditions of an Fe-C of 1 g L-1, PS dosage of 30 mM, MW power of 240 W, and reaction time of 10 min, the UV254, TOC, and CN removal efficiencies were 51.48%, 94.56%, and 51.59%, respectively. In the MW/Fe-C/PS system, a large amount of and a small amount of ˙OH were generated by the thermal activation of PS to remove organic matter. The removal efficiency of organic matter could be further improved via the homogeneous catalytic oxidation and heterogeneous adsorption catalytic oxidation of Fe-C materials. In addition, the MW/Fe-C/PS system was effective for removing refractory organic matter from the leachates from four typical treatment systems: DTRO, SAARB, MBR, and NF. The MW/Fe-C/PS system has the potential to be widely applied for the treatment of landfill leachate.

The role of ozone combined with UVC/H2O2 process for the tertiary treatment of a real slaughterhouse wastewater

The main goal of this work is to evaluate the usage of ozone (O₃) as a pre-treatment or simultaneously combined with UVC/H₂O₂ process for the polishing stage treatment of real bio-treated slaughterhouse wastewater. Two different treatment strategies were tested: i) pre-ozonation of the wastewater followed by an UVC/H₂O₂ process (two-step treatment); ii) simultaneous application of O₃/UVC/H₂O₂ combined process (one-step treatment). For the two-step strategy, the pre-treatment with 30 mg O₃/min for 10 min reduces significantly total suspended solids (TSS), turbidity and colour, reducing light filtering effects and increasing the efficiency of the following UVC/H₂O₂ process. In turn, the one-step treatment strategy (O₃/UVC/H₂O₂) allows a more efficient use of injected O₃ by reducing the amount of O₃ required (from 273 to 189 mg O₃/L_effluent) to achieve similar mineralization levels. The real bio-treated slaughterhouse wastewater treated by O₃/UVC/H₂O₂ process achieved final colour values of 20 Pt/Co, TSS of 35 mg/L and COD of 61 mg O₂/L, allowing its direct discharge into water compartments according to European Council Directive 91/271/EEC.

Advanced Oxidation Processes and Biotechnological Alternatives for the Treatment of Tannery Wastewater

The tannery industry is one of the economic sectors that contributes to the development of different countries. Globally, Europe and Asia are the main producers of this industry, although Latin America and Africa have been growing considerably in recent years. With this growth, the negative environmental impacts towards different ecosystem resources as a result of the discharges of recalcitrated pollutants, have led to different investigations to generate alternative solutions. Worldwide, different technologies have been studied to address this problem, biological and physicochemical processes have been widely studied, presenting drawbacks with some recalcitrant compounds. This review provides a context on the different existing technologies for the treatment of tannery wastewater, analyzing the physicochemical composition of this liquid waste, the impact it generates on human health and ecosystems and the advances in the different existing technologies, focusing on advanced oxidation processes and the use of microalgae. The coupling of advanced oxidation processes with biological processes, mainly microalgae, is seen as a viable biotechnological strategy, not only for the removal of pollutants, but also to obtain value-added products with potential use in the biorefining of the biomass.

Degradation of Landfill Leachate Using UV-TiO2 Photocatalysis Combination with Aged Waste Reactors

This study explored the performance of TiO2 nanoparticles in combination with aged waste reactors to treat landfill leachate. The optimum conditions for synthesis of TiO2 were determined by a series of characterizations and removal rates of methyl orange. The effect of the ultraviolet irradiation time, amount of the catalyst, and pH on the removal efficiency for the chemical oxygen demand (COD) and color in the leachate was explored to determine the optimal process conditions, which were 500 min, 4 g/L and 8.88, respectively. The removal rates for COD and chroma under three optimal conditions were obtained by the single factor control method: 89% and 70%; 95.56% and 70%; and 85% and 87.5%, respectively. Under optimal process conditions, the overall average removal rates for ammonium nitrogen (NH4+–N) and COD in the leachate for the combination of TiO2 nanoparticles and an aged waste reactor were 98.8% and 32.5%, respectively, and the nitrate (NO3−–N) and nitrite nitrogen (NO2–N) concentrations were maintained at 7–9 and 0.01–0.017 mg/L, respectively. TiO2 nanoparticles before and after the photocatalytic reaction were characterized by emission scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and Fourier transform infrared spectrometry. In addition, TiO2 nanoparticles have excellent recyclability, showing the potential of the photocatalytic/biological combined treatment of landfill leachate. This simulation of photocatalysis-landfilling could be a baseline study for the implementation of technology at the pilot scale.

Paraben Compounds—Part II: An Overview of Advanced Oxidation Processes for Their Degradation

Water scarcity represents a problem for billions of people and is expected to get worse in the future. To guarantee people’s water needs, the use of “first-hand water” or the reuse of wastewater must be done. Wastewater treatment and reuse are favorable for this purpose, since first-hand water is scarce and the economic needs for the exploration of this type of water are increasing. In wastewater treatment, it is important to remove contaminants of emerging concern, as well as pathogenic agents. Parabens are used in daily products as preservatives and are detected in different water sources. These compounds are related to different human health problems due to their endocrine-disrupting behavior, as well as several problems in animals. Thus, their removal from water streams is essential to achieve safe reusable water. Advanced Oxidation Processes (AOPs) are considered very promising technologies for wastewater treatment and can be used as alternatives or as complements of the conventional wastewater treatments that are inefficient in the removal of such contaminants. Different AOP technologies such as ozonation, catalytic ozonation, photocatalytic ozonation, Fenton’s, and photocatalysis, among others, have already been used for parabens abatement. This manuscript critically overviews several AOP technologies used in parabens abatement. These treatments were evaluated in terms of ecotoxicological assessment since the resulting by-products of parabens abatement can be more toxic than the parent compounds. The economic aspect was also analyzed to evaluate and compare the considered technologies.

A review of the characteristics of Fenton and ozonation systems in landfill leachate treatment

The development and application of Fenton and ozonation systems in landfill leachate treatment over the last 20 years, and the current research status are reviewed in this paper, with an emphasis on the technical and economic characteristics of Fenton and ozonation systems used to treat different types of landfill leachate. To date, a total of 101 and 78 articles have been published regarding leachate treatment by Fenton and ozonation systems, respectively. These articles considered the use of two systems to treat aged leachate, biologically treated leachate and leachate comprising the concentrated solution resulting from reverse osmosis (RO). The oxidization mechanisms of the two systems used to treat landfill leachate significantly differed in terms of their optimal process parameters (e.g., initial pH value, reagent dosage, and reaction time) and removal efficiency. The Fenton and ozonation systems outperformed persulfate-based advanced oxidation technology in terms of their improved biodegradability of landfill leachate and engineering practicability. The cost of the reagents required to treat landfill leachate by Fenton and ozonation systems accounted for at least 85% of the total operating cost. In contrast to the ozonation system, the Fenton system was more cost-effective when both systems were used to treat the same type of landfill leachate. This study provides a theoretical basis for the operation of Fenton and ozonation systems and also offers technical support for landfill leachate disposal companies that opt to use these technologies.

Removal of sulfadiazine from simulated industrial wastewater by a membrane bioreactor and ozonation

Ozonation can be used as a polishing treatment for degrading low-concentration pharmaceutical compounds recalcitrant to biological treatment, when large amounts of biodegradable organics have been previously removed by biological processes. Nevertheless, a systematic investigation has not yet been carried out for the coupled MBR + O₃ process through an experimental design approach. Thereby, the purpose of this study is to evaluate the performance of different processes (membrane bioreactor-MBR, ozonation; and integrated MBR + O₃) for removing the antibiotic sulfadiazine (SDZ) from a synthetic wastewater matrix of industrial interest. The MBR behavior was monitored over seven months for different parameters (pH, temperature, permeate flow, transmembrane pressure, biological oxygen demand-BOD₅, chemical oxygen demand-COD, total organic carbon-TOC, solids, and SDZ concentration). Additionally, the amount of SDZ sorbed onto the sludge was characterized, an issue which is scarcely addressed in most research works. Ozonation experiments were conducted in batch mode in a 2-L glass reactor provided with openings for gas flow. For the MBR + O₃ process, the effects of gas flow rate (0.1-1.5 L min^-1) and inlet ozone concentration (4-12 mg L^-1) on SDZ removal from the MBR permeate were systematically assessed using a Doehlert experimental design and response surface methodology. The results indicated that the MBR system showed good performance regarding organic matter removal efficiency, evaluated in terms of BOD₅ (91.5%), COD (93.1%) and TOC (96.3%). In contrast, SDZ was partially removed (33%) by the MBR; in that case, the results indicated that the antibiotic was moderately removed with the sludge and partially biodegraded. In turn, the MBR + O₃ system showed excellent performance for removing SDZ (100%), TOC (97%), BOD₅ (94%) and COD (97%). The statistical analysis confirmed that the influence of ozone gas flow rate upon the SDZ removal rate was more important than that exhibited by inlet ozone concentration. Therefore, coupling MBR and ozone can be considered a promising alternative for point source treatment of antibiotic production wastewater.