Table Olive Processing Wastewater Research Articles

Enhanced biomass and lipid production from olive processing wastewater using Scenedesmus obliquus in a two-stage cultivation strategy under salt stress

The study enhanced Scenedesmus obliquus cultivation via optimization of C/N and C/P ratios in synthetic media and evaluation of a two-stage cultivation strategy through application of salinity stress in olive processing wastewater-based feedstocks. S. obliquus under 40/1 C/N ratio performed biomass and lipid productivity that reached 0.15 and 34.1 mg L−1 d−1 respectively, demonstrating high glucose removal efficiency. Application of a two-stage cultivation strategy employing 0, 10, 20 and 30 g L−1 NaCl during the second bioprocess segment resulted in elevated biomass productivity (0.14–0.19 g L−1 d−1), which was reduced under batch mode yielding 0.11 g L−1 d−1. Two-stage cultivation triggered higher lipid productivity (4.2%-156.9%) following 3 d and 6 d upon the onset of the second stage (42.7–55.2 mg L−1 d−1) as compared to batch conditions, while the utilization of reducing sugars in exhausted olive pomace hydrolysates and table olive processing wastewater reached 53.6%-61.2%. Proline, glycerol and reactive oxygen species accumulated at considerable levels employing 20 and 30 g L−1 NaCl, indicating that S. obliquus expressed cellular stress under elevated salinity content, which was not notably stimulated using 10 g L−1 NaCl. The use of olive processing wastewater in a two-stage cultivation strategy under stress conditions enables future development of algal biorefinery systems for production of S. obliquus biomass and polyunsaturated fatty acids as high added-value products from biowaste.

Αpplication of Aspergillus niger for Extracellular Tannase and Gallic Acid Production in Non-sterile Table Olive Processing Wastewaters

Aspergillus niger B60 was screened for the first time toward extracellular tannase and gallic acid production by submerged fermentation using synthetic media supplemented with tannic acid as the sole carbon source at a wide concentration range (5–150 g/L). Maximum tannase (47 IU/mL) and gallic acid production (36 g/L) was obtained at initial tannic acid concentration 100 g/L. For this study, it was of interest to valorize non-sterile table olive processing wastewaters for fungal tannase production. In particular, lye and washing water effluents from Spanish-style green olive processing enriched with 100 g/L tannic acid provided effective alternative substrates for the production of tannase (21 IU/mL and 17 IU/mL, respectively) and gallic acid (22 g/L and 14 g/L, respectively). The fungal growth and tannase production kinetics were described by the Logistic and Luedeking–Piret models, respectively. The maximum dry biomass content and the maximum specific growth rate were more pronounced in the tannic acid-rich effluents (16–18 g/L and 0.5–0.6 1/h, respectively) than in the synthetic medium (11 g/L and 0.4 1/h, respectively) although in all cases tannase production was growth-associated. These novel findings cast a new light on successful biorefinery strategies of the effluents and warrant further investigation via process scaling-up and optimization.Graphical

Phenolic compounds removal in table olive processing wastewater by column adsorption: conditions' optimization.

The annual production of wastewater from the olive table industry poses a serious problem owing to its high organic matter load, which is highly concentrated in phenolic compounds (PCs) and inorganic materials. This research used adsorption to recover PCs from table olive wastewater (TOWW). Activated carbon was employed as a novel adsorbent. The activated carbon was obtained from olive pomace (OP) and activated using a chemical agent (ZnCl2). Fourier transform infrared spectroscopy analysis (FTIR), Brunauer-Emmett-Teller analysis (BET), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) were applied to characterize the activated carbon sample. To optimize the biosorption conditions of PCs (adsorbent dose (A), temperature (B), and time (C)), a central composite design (CCD) model was used. An adsorption capacity was 1952.34mgg-1 for optimal conditions with an activated carbon dose of 0.569g L-1, a temperature of 39°C, and a contact time of 239min. The pseudo-second-order and Langmuir models as kinetic and isothermal mathematical models were proved to be more appropriate for the interpretation of the adsorption phenomenon of PCs. PC recovery was performed in fixed-bed reactors. The results of the adsorption of PCs from TOWW by activated carbon could be an effective process at a low cost.

Biorefinery development for the production of polyphenols, algal biomass and lipids using olive processing industry waste

A biorefinery was developed employing olive pomace and table olive processing wastewater for the manufacture of polyphenols, lipids and algal biomass. Following extraction of pomace oil, olive pomace was subjected to dilute acid hydrolysis and enzyme hydrolysis under different conditions aiming to maximise the content of polyphenols and sugars formed in the hydrolysate produced for application in subsequent resin adsorption/desorption and microalgal fermentation processes. Hydrolysis of 100 kg exhausted olive pomace performed under the most efficient conditions yielded release of 54.5 kg of sugars and 3.2 kg of polyphenols. Polyphenols were recovered from olive pomace hydrolysates and table olive processing wastewater via adsorption/desorption employing different polymeric resins. Application of XAD16N and PAD900 resins exhibited the highest overall polyphenols recovery, that reached 79.5% and 58.0% for table olive processing wastewater and exhausted olive pomace extracts respectively. The hydrolysates generated following polyphenols recovery were evaluated as feedstocks for lipids production by Scenedesmus obliquus and Isochrysis galbana, demonstrating maximum biomass and lipid productivity that reached 190 mg L−1 d−1 and 61.4 mg L−1 d−1 for S. obliquus, as well as 32 mg L−1 d−1 and 8.4 mg L−1 d−1 for I. galbana respectively. I. galbana accumulated high docosahexaenoic acid content that ranged between 8.4 and 9.5 mg g−1 of ash-free dry weight in fermentations of the hydrolysates developed confirming that the strain could serve as an advanced bioproducer of polyunsaturated fatty acids in microalgal biorefineries.

Soil Salinity Patterns in an Olive Grove Irrigated with Reclaimed Table Olive Processing Wastewater

The agricultural use of saline table olive processing wastewater enables the implementation of closed water cycles in this socioeconomically important industry for rural southern Spain and relieves environmental, economic, and legal burdens. To allow growers to evaluate and guarantee adequate long-term soil and plant conditions when irrigating with such regenerated wastewaters, efficient soil monitoring strategies are needed. Field-scale monitoring with electromagnetic induction sensing, after one (2013) and five years (2017) of irrigation with regenerated wastewater with average electrical conductivity (EC) near 6 dS m−1 in an olive orchard in southern Spain, showed accumulation of highly conductive material in the subsoil in relation to local topography and soil characteristics. Laboratory analysis of the soil water revealed strongly varying patterns of EC during the growing season and across the olive grove, which were attributed to dilution and concentration effects due to rainfall and evaporation, respectively. Visual inspection and leaf analyses revealed no negative effects on the olive trees. Apparent electrical conductivity (ECa), measured in between the tree rows in 2013, showed a linear relationship with surface soil EC1:5 under the drippers and allowed identification of areas with high ECa in the low elevation zones of the farm, due to the presence of shallow perched saline water tables. A second ECa measurement in 2017 showed similar spatial ECa patterns and was used to estimate the distribution of soil EC across the soil profile using inversion software, although no unique field-wide relationships with soil properties could be inferred, possibly as a consequence of spatially variable soil clay and water contents, due to the influence of the topography. Despite the implementation of a more conservative irrigation strategy since 2015, results showed that the salinity has increased since 2013 in about 15% of the study area, with the largest increments in the deepest horizons.

Removal of Phenols in Table Olive Processing Wastewater by Using a Mixed Inoculum of Candida boidinii and Bacillus pumilus: Effects of Inoculation Dynamics, Temperature, pH, and Effluent Age on the Abatement Efficiency.

The main goal of this paper was to assess the ability of a combination of Candida boidinii and Bacillus pumilus to remove phenol in table olive processing water, as a function of some variables, like temperature, pH, a dilution of waste and the order of inoculation of the two microorganisms. At this purpose C. boidinii and B. pumilus were sequentially inoculated in two types of table olive processing water (fresh wastewater, FTOPW and wastewater stored for 3 months-aged wastewater, ATOPW). pH (6 and 9), temperature (10 and 35 °C) and dilution ratio (0, 1:1) were combined through a 2k fractional design. Data were modeled using two different approaches: Multifactorial Analysis of Variance (MANOVA) and multiple regression. A higher removal yield was achieved by inoculating B. pumilus prior to the yeast (192 vs. 127 mg/L); moreover, an increased efficiency was gained at 35 °C (mean removal of 200 mg/L). The use of two statistic approach suggested a different weight of variables; temperature was a global variable, that is a factor able to affect the yield of the process in all conditions. On the other hand, an alkaline pH could increase the removal of phenol at 10 °C (25–43%).

Membrane filtration, activated sludge and solar photocatalytic technologies for the effective treatment of table olive processing wastewater

The table olive industry produces a high quantity of wastewater (TOPW) whose management represents a challenge due to its environmental risk. TOPW samples from an industrial site were characterized and different individual and integrated treatment methods were applied and their efficiency compared. Aerobic biodegradation (i.e., activated sludge) and TiO2 solar photocatalysis were not able to effectively treat raw TOPW mainly due to slow organic matter removal and excessive electrical conductivity (EC) of the resulting effluents (c.a. 10 mS·cm−1). Reverse osmosis (RO) and nanofiltration (NF) treatments of TOPW, however, showed good results in terms of removals of chemical oxygen demand (COD, 82–93%), total phenols (TP, 81–100%) and EC (60–98%). The effects of several pre-treatments of TOPW (i.e., microfiltration, coagulation-flocculation, biodegradation and solar photocatalysis) on the performance of NF and RO membranes were studied. MF pre-treatment increased the permeate flux recovery in NF and allowed the membrane to be satisfactorily reused. The NF effluent could be successfully subjected to either aerobic biodegradation or solar TiO2 photocatalytic post-treatment in order to fulfill requirements for discharge into the municipal sewage system.

Performance of a membrane bioreactor and a moving bed biofilm reactor–membrane bioreactor treating table olive processing wastewater: a comparative study

AbstractBACKGROUNDTwo laboratory‐scale experimental systems – a membrane bioreactor (MBR) and a moving bed biofilm reactor–membrane bioreactor (MBBR‐MBR), both treating real high‐strength, saline wastewater from a table olive processing plant – were operated under identical conditions to comparatively evaluate their performance for three different hydraulic retention times (HRTs) of 88, 96 and 104 h.RESULTSThe biological process of both systems, after appropriate biomass acclimatization, was stable and the removal efficiencies were rather high; i.e., regarding total organic carbon (TOC) ≥86.4% and ≥85.6% for the MBR and MBBR‐MBR, respectively, and ≥89.1% regarding total polyphenols (TPh) for both systems. Concerning TOC and TPh removal, no statistically significant difference (p < 0.05) was observed between the two systems. Reduction of HRT resulted in a slight decrease in mean TOC removal efficiency, but the mean TPh removal was practically unchanged. No membrane chemical cleaning was applied to either system during the 85‐day long continuous operation.CONCLUSIONThe comparative assessment showed that both systems (i.e., MBR and MBBR‐MBR) are effective for the advanced biological treatment of table olive processing wastewater and can achieve quite high removal efficiencies of organic matter and TPh. However, direct effluent reuse for irrigation purposes seems to be hindered by its high salinity. No significant differences were observed in the performance of these systems, apart from the increased aeration (and related energy costs), which is necessary to keep the biofilm carriers floating in the case of the MBBR‐MBR. © 2020 Society of Chemical Industry

Management of table olive processing wastewater by an osmotic membrane bioreactor process

The management of fermentation brines from the table olive processing is very complex due to its characteristics: high salinity and high organic matter concentration including phenolic compounds, which behave as slow degradable compounds when a biological process is performed. In this work, the management of these effluents by an osmotic membrane bioreactor has been assessed. This technique combines a biological reactor with forward osmosis membranes. For the study, a laboratory plant consisting of 1 L reactor and a forward osmosis module equipped with a membrane of 42 cm2 of active surface has been used. Fermentation brine from table olive processing was fed to the system both as draw solution to set out the driving force for the membrane process and as a part of the feed to the reactor, mixing it with municipal wastewater. The experiments were carried out at a constant feed to microorganism ratio of 0.4 g COD·g SS−1·d−1. Results indicated that the hypersaline effluent was able to produce the needed driving force by the process. Permeate fluxes ranged between 1 and 1.5 L·m−2·h−1 after the flux decay of the first operation days. Concerning the biological reaction, it has to be highlighted that phenols were eliminated after 24 days. Until that day, the biological process was jeopardized due to the quick increase of the conductivity in the reactor (ranging between 30 and 35 mS·cm−1), which was caused not only by the salinity of the influent but also by the reverse salt flux phenomenon. Soluble microbial products and extracted extracellular polymeric substances also increased in the reactor during the start-up.

Analysis of Microbial Community Dynamics during the Acclimatization Period of a Membrane Bioreactor Treating Table Olive Processing Wastewater

Biological treatment of table olive processing wastewater (TOPW) may be problematic due to its high organic and polyphenolic compound content. Biomass acclimatization is a necessary, yet sensitive, stage for efficient TOPW biological treatment. Next-generation sequencing technologies can provide valuable insights into this critical process step. An aerobic membrane bioreactor (MBR) system, initially inoculated with municipal activated sludge, was acclimatized to treat TOPW. Operational stability and bioremediation efficiency were monitored for approx. three months, whereas microbial community dynamics and metabolic adaptation were assessed through metagenomic and metatranscriptomic analysis. A swift change was identified in both the prokaryotic and eukaryotic bio-community after introduction of TOPW in the MBR, and a new diverse bio-community was established. Thauera and Paracoccus spp. are dominant contributors to the metabolic activity of the stable bio-community, which resulted in over 90% and 85% removal efficiency of total organic carbon and total polyphenols, respectively. This is the first study assessing the microbial community dynamics in a well-defined MBR process treating TOPW, offering guidance in the start-up of large-scale applications.

Treatment of table olive processing wastewaters using electrocoagulation in laboratory and pilot-scale reactors

Electrocoagulation-(EC) is investigated as an alternative, cost-efficient, method for the treatment or post-treatment of table olive processing wastewaters (TOPWs). Experiments were performed in both laboratory and pilot-scale reactors using aluminum and iron electrodes. Different initial chemical oxygen demand (COD) concentrations (3000, 5000 and 9000mgL−1) and current densities (41.7, 83.3 and 166.7mA cm-2) were tested in laboratory-scale experiments to determine maximum COD and color removal from untreated TOPWs. Pilot-scale experiments were also conducted using biologically pre-treated TOPW (COD 1000mgL-1 and current densities of 3.87 and 5.65mA cm-2) to ensure an efficient post-treatment process. Aluminum electrodes were found to be more efficient in reducing COD and color than iron electrodes in both laboratory and pilot-scale experiments. In laboratory-scale experiments the maximum COD and color removal (approximately 50% and 100%, respectively) was recorded for the lowest initial COD concentration of 3000mgL−1 at 166.7mA cm-2. In the pilot-scale reactor the maximum COD and color removal observed was 42.5% and 85.3%, respectively, for the current density of 5.65mA cm-2. Lower energy and electrode consumption was recorded when working with aluminum electrodes and optimum results were obtained with the lowest initial COD and current density values tested.

Treatability studies on optimizing coagulant type and dosage in combined coagulation/membrane processes for table olive processing wastewater

A considerable amount of process water has been consumed by table olive industry. As a result of the process, large volumes of table olive process wastewater (TOPW) are released with a high value of chemical oxygen demand (COD), a significant amount of suspended solids (SS) and conductivity. So, the treatment of TOPW becomes more important due to its toxic impacts on the environment and stringent regulations about the discharging. This study aims to investigate the treatability of real TOPW by integrated wastewater treatment technology which was comprised of chemical coagulation/flocculation and membrane processes. In chemical treatment studies, optimum types and dosages of coagulants/flocculants and operating pH were examined. In membrane treatment studies, the supernatant of the coagulated/flocculated wastewater was further treated by advanced membrane filtration technologies which contain ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO). UF membrane was used as a pretreatment prior to NF/RO membranes with a 46.7% COD removal efficiency. Then, types of NF/RO membranes and operating pH were optimized. The limit values for discharging standards were provided for both RO membranes which contained COD value lower than 150 mg/L. As a conclusion, an integrated membrane process represents a promising alternative for the treatment of TOPW.

Assessing biomass diversity and performance of an activated sludge process treating saline table olive processing wastewater

ABSTRACTThis study aimed to determine the effects of salinity on the biomass behavior and its diversity in activated sludge process (ASP) treating the table olive processing wastewater (TOPW), and to evaluate ASP performances under increased TOPW concentration feeding, the numerical abundance, diversity and activity of the biomass, removal efficiencies of chemical oxygen demand (COD), phenolic compounds, nitrogen and phosphorus were evaluated. Results showed that biomass growth is very high and became faster according to an increase in the percentage of TOPW feeding and reached 5.2 gMLVSS l−1. The specific oxygen uptake rate (SOUR) analysis revealed that salinity up to 10 g l−1 provides an increase in biomass activity. SOUR reached a maximum of 20.3 gO2 gMLVSS−1 h−1. The increasing percentages of TOPW induce actually an evolution of microorganism's biodiversity; the microorganism communities were characterized by the abundance of halotolerant, Pseudomonas and Yeast genus that became the most abundant in the bioreactor as adaptation response against salinity. Furthermore, COD, phenolic compounds, nitrogen and phosphorus removal efficiencies attained 92.3%, 84.5%, 80% and 60%, respectively. A satisfactory release of extracellular polymeric substances is found to occur in the reactor with regard to increased saline TOPW, providing significant removal efficiencies and best settling of sludge.

Recovery of phenolic compounds from table olive processing wastewaters using cloud point extraction method

Table olive processing wastewaters lead to large environmental problems mainly due to its relatively high phenolic content. In the present study, the Cloud Point Extraction (CPE) technique was used to preconcentrate the natural phenolic compounds from table olive processing wastewaters (TOPW) using three different nonionic surfactants: Genapol X-080, Triton X100 and Tween 80. The optimum conditions for the CPE of phenolic compounds were studied with respect to different experimental parameters, surfactant concentration, pH of the solution, equilibrium temperature and incubation time. The most appropriate conditions were found to be 10% of surfactant (w/v), a pH value of 2, a temperature of 70 °C and an equilibrium time of 30 min. The recovery factors of phenolic compounds from TOPW with one step CPE under optimized conditions were 62%, 65% and 68% using 10% of Tween 80, Triton X100 and Genapol X-080, respectively.

Advanced oxidation process and biological treatments for table olive processing wastewaters: constraints and a novel approach to integrated recycling process: a review.

Table olive processing wastewaters constitute a dangerous environmental problem in the Mediterranean countries because of their large volumes, high organic matter and salt concentration. The quantity and the characteristics of wastewaters produced, and thus, their environmental impact, varied depending on the season, varieties, soil and process employed. Several chemicals, biological and combined technologies have proven effective at bringing down organic pollution and toxicity of these effluents. Advanced oxidation processes have recognized as highly efficient treatments for the degradation of organic matter. Nonetheless, complete mineralization is generally expensive without salt removal. Biological processes are the most environmentally compatible and least-expensive treatment methods, but these operations do not always provide satisfactory results. This article surveys the current available technologies and suggests an effective, cheaper alternative for the recycling and the valorization of green table olives wastewaters.

Chemical composition and direct electrochemical oxidation of table olive processing wastewater using high oxidation power anodes

Table olive processing wastewater (TOW) is a notoriously polluting due to its high organic and phenol content. To reduce them, an electrochemical process has been studied for the treatment of this effluent. Experiments were performed with a cell equipped with lead dioxide (PbO2) or boron-doped diamond (BDD) as anode and platinum as cathode, where Table Olive Wastewater (TOW) were destroyed by hydroxyl radicals formed at the anode surface from water oxidation. The comparative study of both systems shows the performance of the BDD anode compared to PbO2, explained by the large amounts of hydroxyl radicals generated effective at BDD anode and its synthesis characteristics.Using LC/MS analysis, it was possible to determine hydroxytyrosol, as major phenolic compounds, in table olive processing wastewater and its concentration reach 890 mg L−1. A possible reaction mechanism oxidation for hydroxytyrosol was proposed. The kinetics decays for hydroxytyrosol degradation on PbO2 anode follows a pseudo-first order reaction with a rate constant 0.9 h−1 for japp value 20 mA cm−2.

Effect of alternating anaerobic and aerobic phases on the performance of a SBR treating effluents with high salinity and phenols concentration

The biological treatment of hypersaline wastewaters with high COD and phenols concentration requires long hydraulic retention times and much energy for aeration. In this work aeration time reduction in the reaction phase was studied in two sequential batch reactors (SBR) treating fermentation brine from table olive processing wastewater. To study the influence of an anaerobic phase on the SBR performance (for COD and phenolic compound removal efficiencies), different anaerobic/aerobic reaction times were evaluated. SBR-1 was operated with an anaerobic/aerobic hours ratio of 0/22, 8/14 and 14/8 and SBR-2 with a ratio of 22/0, 14/8 and 8/14. Results showed that the maximum organic matter reduction was obtained under aerobic reaction conditions (ratio 0/22) with a 82.3% and 77.9% of COD and total phenols removal, respectively. However, optimal conditions were considered to prevail for an anaerobic/aerobic ratio of 8/14, since the reactors performances were similar with lower energy consumption. Thus, 82.3% and 79.5% of COD and 77.9% and 78.3% of total phenols were removed in SBR-1 and SBR-2, respectively.

Bioelectrochemical treatment of table olive brine processing wastewater for biogas production and phenolic compounds removal

Industry of table olives is widely distributed over the Mediterranean countries and generates large volumes of processing wastewaters (TOPWs). TOPWs contain high levels of organic matter, salt, and phenolic compounds that are recalcitrant to microbial degradation. This work aims to evaluate the potential of bioelectrochemical systems to simultaneously treat real TOPWs and recover energy. The experiments were performed in potentiostatically-controlled single-chamber systems fed with real TOPW and using a moderate halophilic consortium as biocatalyst. In conventional anaerobic digestion (AD) treatment, ie. where no potential was applied, no CH4 was produced. In comparison, Bio-Electrochemical Systems (BES) showed a maximum CH4 yield of 701 ± 13 NmL CH4·LTOPW−1 under a current density of 7.1 ± 0.4 A m−2 and with a coulombic efficiency of 30%. Interestingly, up to 80% of the phenolic compounds found in the raw TOPW (i.e. hydroxytyrosol and tyrosol) were removed. A new theoretical degradation pathway was proposed after identification of the metabolic by-products. Consistently, microbial community analysis at the anode revealed a clear and specific enrichment in anode-respiring bacteria (ARB) from the genera Desulfuromonas and Geoalkalibacter, supporting the key role of these electroactive microorganisms. As a conclusion, bioelectrochemical systems represent a promising bioprocess alternative for the treatment and energy recovery of recalcitrant TOPWs.

Current status and future challenges of table olive processing wastewater valorization

Table olive production is expanding worldwide. This production is associated with the generation of enormous amounts of polluting and difficult to handle wastewater streams. Thus, research on different technologies to decompose their organic load is currently needed. The economic benefit of the potential detoxification routes is expected to increase if processes for upgrading Table olive processing wastewaters are designed. This makes biological treatment of particular interest. The current review analyzes a relevant number of scientific studies dealing with promising technologies for biological treatment of table olive processing wastewaters from laboratory to pilot-scale systems. Concise details of the various technologies involved such as anaerobic digestion, lactic acid fermentation and fungal fermentation are determined. The most significant advances in the manufacturing of value-added products (e.g. biogas, platform chemicals, natural antioxidants) from table olive processing wastewaters through different microorganisms, bioreactor design modifications, and operational conditions are critically discussed. Future prospects of valorizing table olive wastewaters are presented.

A hybrid system comprising an aerobic biological process and electrochemical oxidation for the treatment of black table olive processing wastewaters

In this work table olive processing wastewaters (TOPW) were treated by aerobic biological processes using indigenous microorganisms originating from TOPW, as well as the combination of two successive steps, i.e. aerobic biological treatment followed by electrochemical oxidation over a boron-doped diamond anode.In the single aerobic biological processes, experiments in suspended and attached growth reactors (trickling filters) were carried out using different TOPW feed concentrations of 5500 ± 350, 7500 ± 650 and 15,000 ± 1050 mg dissolved COD L−1. Two different operating modes were used to investigate the optimum performance of the filter, i.e. batch and SBR with recirculation. The latter mode with recirculation of 0.5 L min−1 led to high removal rates of dissolved COD and total phenolic compounds, up to 96.5% and 64.5%, respectively, for the initial COD concentration of 7500 mg dissolved COD L−1.Depending on the type and operating conditions of the bioreactors, residual COD ranged between a few hundred and a few thousand mg L−1, while decolorization could not be achieved even under the most favorable conditions. A biologically treated effluent with residual dissolved COD of 5100 mg L−1 was completely mineralized and decolorized at 187.5 mA cm−2 applied current density; complete removal of COD, color and total phenolic compounds was achieved in 180–240 min, 30–60 min and 30 min of electrochemical oxidation, respectively. Lower treatment times and current densities were needed to polish effluents with lower organic loads.