Effluent Alkalinity Research Articles

First full-scale application of barium carbonate as an effective dispersed alkaline substrate for sulfate removal from acid mine drainage

A full-scale passive treatment plant using barium carbonate (BaCO3), the mineral witherite, as a Dispersed Alkaline Substrate (DAS) for strongly contaminated acid mine drainage was implemented for the first time globally at Mina Concepción, located in the Iberian Pyrite Belt (SW Spain). The plant was monitored over a 105-day period, covering the wettest months of the hydrological year and with a mean flow around 4 L s−1. The AMD treated in the plant exhibits a high strength, with an average sulfate concentration around 1500 mg L−1 and net acidity close to 1000 mg L−1 as CaCO₃ equivalent. According to the above, the loading rate for SO4 and Fe was around 400 and 80 kg day−1, respectively. The treatment process produced an alkaline effluent with low metal content. Nearly complete removal of most metal(loid)s was achieved, with significant sulfate decrease to below 500 mg L−1 in the alkaline outflow of the barium carbonate tank. Barium carbonate demonstrated superior performance compared to magnesia, particularly in enhancing alkalinity and lowering net acidity and concentrations of sulfate and manganese. The high efficiency attained by the plant after the barium carbonate treatment is evidenced by compliance with environmental water quality standards for most contaminants.

Understanding Electrochemical and Mechanical Durability of Bipolar Membranes Used in Electrodialysis

Using renewable energy to drive direct carbon capture systems is a powerful way to contribute to net negative emissions. When using liquid alkaline sorbents for CO2 direct air capture, it is critical to reduce the energy demand for CO2 concentration and sorbent regeneration. Electrodialysis is an ideal candidate technology to integrate renewable energy into this process, however, to enable this ion-exchange membrane separators that can operate at high ion flux and low voltage are needed. Bipolar membranes (BPMs), that generate protons and hydroxide ions from the dissociation of water when operated in reverse bias, are the enabling component to generate acid and base in electrodialysis systems. Bipolar membrane electrodialysis (BPMED) uses a BPM to create acidifying and basifying chambers which are well suited to concentrate and release CO2 and concentrate the remaining alkaline effluent to cycle back to the capture process. Current BPM durability, however, sufferers at high current density (ion flux) and physical scale. BPMs have several known degradation mechanisms including chemical breakdown of ion exchange polymers, loss of junction adhesion, or physical breakdown due to shearing force and pressure swings in an electrodialysis cell.To assess the electrochemical and mechanical durability of BPMs under operational conditions, we investigated how fabrication conditions (including preconditioning, hot pressing, and catalyst loading) impact the adhesion of custom made BPMs. T-peel studies were performed ex-situ to quantify adhesive forces of BPMs made of different compositions and prepared under different conditions, and BPMED experiments were performed to assess the electrochemical performance of the corresponding BPMs. The BPMED results show that, while adhesion is necessary to physically maintain the BPM junction, mechanical adhesion alone cannot overcome poor ion and water transport management at the water dissociation junction. The results of this systematic comparison indicate that in order for BPMs to operate at high current densities, high adhesion forces made during fabrication of BPMs will need to be balanced with water dissociation kinetics and ion/water transport through the individual membrane layers.

Coupled electrochemical crystallization-electrocoagulation-flocculation process for efficient removal of hardness and silica from reverse osmosis concentrate

The benign electrochemical technologies are the promising methods for the reuse of reverse osmosis concentrate (ROC) by softening and removing silica, whereas its low treatment performance and high energy consumption limit its wide industrial application. In this study, an undivided electrochemical crystallization cell with the extraction of acid anode boundary layer was developed for the production of the alkaline effluent, where the removal of hardness and silica occurred by the homogeneous crystallization reactions. This process was further improved in the electrocoagulation cell because coagulants enhance the removal of crystalline particles and accelerate the settling of the crystals. Under optimal conditions, the system showed a removal efficiency of 90 % for total hardness, 76 % for Mg hardness, and 82 % for silica, with an energy consumption of only 2.4 kWh m−3. The removal of Ca hardness in the forms of calcite and aragonite was impeded by the presence of Mg2+. But the coexistence of silica promoted Ca hardness removal since the reaction between Mg2+ and silica with the formation of sepiolite mitigated the inhibitory effect of Mg2+ on CaCO3 precipitation. The coupled electrochemical crystallization-electrocoagulation-flocculation technique provides an energy-efficient solution for the removal of hardness and silica from ROC, therefore improving the water utilization in industry.

High-flux electrochemical phosphorus recovery in an undivided electrolytic cell coupled with microfiltration with low energy consumption

Electrochemical systems are promising for phosphorus (P) removal and recovery from wastewater. However, its industrial application still faces some challenges, including relatively low P recovery efficacy, high energy consumption, and complex configuration of the reactors. This work, developed an undivided electrolytic cell with H+ or OH− extraction from its corresponding electrode surface for P recovery. The experimental results and models validated the superiority of continuously and precisely extracting H+ from the tubular Ti porous anode surface for H+–OH− separation over OH− extraction from the cathode surface. In the electrolytic cell, alkaline effluent with H+ extraction, the P could be precipitated with Ca2+ in the form of insoluble calcium phosphate (Ca-phosphate), which could then be separated from the wastewater by microfiltration. Under the conditions of a current density of 4 mA cm−2, an initial P concentration of 0.6 mM, a influent flow rate of 500 mL min−1, and H+ extraction rate of 50 mL min−1, the P recovery efficiency reached 81 % with the alkaline effluent pH of 10.5. The calculated P recovery rate and treatment capacity were 18.3 g P (m2 h)-1 and 1194 L (m2 h)-1, respectively, at energy consumption of 8.75 kWh (kg P)-1, which were superior over the cutting-edge divided electrolytic systems and the conventional undivided electrolytic systems. The recovered precipitates are composed principally of hydroxyapatite in the minor presence of amorphous calcium phosphate, showing a Ca/P molar ratio of 1.8. Generally, the established undivided electrolytic cell coupled with microfiltration exhibited significant prospects for recovering P from wastewater without acid-base reagents.

Interference free ultratrace beryllium determination in alkaline effluents of beryllium processing plants by graphite furnace atomic absorption spectrometry after a novel graphene oxide-assisted dispersive micro solid phase extraction without using a chelating agent

Ultratrace level determination of beryllium is carried out using graphene oxide as a dispersive micro solid phase extractant in alkaline beryllium processing plant effluents.

Risk Assessment of Hydrogen Sulfide (H₂S) Gas and Its Impact on Human Health: Evidence from Tannery Industry of a Developing Country

Hydrogen sulfide (H₂S) gas is quite risky and harmful for the tannery industry workers in Bangladesh. A proper measurement or assessment of this risk will help policymakers make crucial policy decisions, which will surely help the continued positive growth of this industry. This study has three specific objectives: identifying potential sources of hydrogen sulfide gas generation, assessing the root causes of hydrogen sulfide gas generation, and suggesting proper activities to reduce the impact of hydrogen sulfide gas generation. In order to carry out this study, a qualitative approach has been used, where qualitative data are used to find out the results. It started with reviewing the secondary documents but also included key informant interviews (KIIs), focus group discussions (FGDs), and a sample survey. This study has collected data from 20 different tanneries. Out of 20 tanneries, 80 respondents were selected via the purposive sampling method. Information has been taken from 80 respondents via Key Informant Interviews and Focused Group discussions, where each group consists of a different number of individuals and is selected on the basis of the location of the production process in tanneries. The study has found major sources and causes of H₂S generation. The major sources include the tanning chemical store, pre-tanning (Beam house area), Re-tanning area, Chrome effluent drain, Mix effluent drain, etc. The major causes of H₂S gas generation include intermixing of incompatible chemicals, lack of proper cleanliness, reaction of liming liquors, etc. The study also suggested various measures such as proper ventilation, separating chromium and re-tanning effluent from alkaline effluent, and reducing solid waste.

Ionization‐engineered two‐dimensional confined channels in GO membranes for highly efficient OH− separation

AbstractOH− sieving membranes provide a valuable means for treating alkaline effluents but their development presents several challenges. In this study, the concept of ionization engineering is applied to two‐dimensional (2D) laminated membranes to facilitate OH− separation. This concept is demonstrated through the stacking of the self‐designed sulfonated graphene oxide (SGO) nanosheets to fabricate 2D membranes. The SGO membranes enhance synergistically the OH− dialysis coefficients and separation factors when treating simulated NaOH/Na2WO4 alkaline wastewater, compared with the performance of 2D GO membranes and commonly adopted polymeric cation exchange membranes. Furthermore, the separation factor achieved by the SGO membranes is considerably higher than that of most of the existing alkali recovery membranes. Results of molecular dynamics simulations indicate that the high efficiency of OH− separation in the 2D SGO confined channels is attributable to dehydration effects and intensified electrostatic repulsion. Overall, this research provides an alternative strategy for achieving rapid OH− sieving through the ionization of 2D confined channels.

Application of alternative organic wetland media for acid mine drainage treatment: Insights on reformations of microbial community structure

Acid mine drainage (AMD) discharge, particularly from the North Eastern Coalfield (NEC), Assam, has been a major persistent ecological threat. A lab-scale constructed wetland (CW) deriving organic wastes as the wetland media was implemented to treat high acidity (724 mg L–1 as CaCO3) AMD loaded with sulfate (1000–1300 mg L–1). Metal contents in mine wastewater comprised iron, aluminium, manganese, zinc, cobalt, nickel and chromium as 104, 25, 6.2, 5.1, 1.1, 1.1 and 1.1 mg L–1, respectively. CW operated continuously at a hydraulic loading rate (HLR) of 0.03 m3 m–2 d–1 for 282 days. Effluent water quality was monitored, and resulting shifts in microbial diversity were identified. Results demonstrated 771 mg L–1 (as CaCO3) alkalinity in effluent and metal removal (87–100%), except Co and Mn, which surpassed effluent discharge criteria. Further, the high-throughput sequencing results revealed significant reformations in bacterial assemblages throughout the operational period. Proteobacteria (45%) and Bacteroidetes (26%) represented the major bacterial groups at the start-up of CW, which later declined due to the elimination of aerobic strains under anaerobic conditions. Additionally, methanogenic archaea suppressed greatly due to the competition from sulfate and iron-reducers. An increase in the relative abundances of key functional bacteria (Firmicutes, Bacteroidetes, Actinobacteria and Acidobacteria) in the treatment phase indicated stable operation. Sulfate reduction (62%) was partial, evidenced by the prominence of sulfate-reducing bacteria (SRB) (Thermodesulfobium, Syntrophobacter, Desulfomonile and Desulfovibrio). This study offers insights into the microbial dynamics within an organic-media-amended CW, which directly influences AMD treatment.

Study of influence of iron, phosphorus, potassium, tantalum and fluorine on the properties of TiNb2O7

Recently, niobium-based oxides have attracted increasing interest as a potential choice for lithium-ion battery technology. The mixed oxide of niobium and titanium, in the composition of TiNb2O7, has been considered a promising candidate for the anodic materials of new generation lithium-ion batteries. However, its precursors require a severe and costly purification process since they are processed from complex ores. In addition to the purification cost, these steps result in significant amounts of acid and alkaline effluents, which generate additional costs for their treatment. The present research was designed to understand the influence of contaminants commonly found in ores or inserted in the process routes to obtain niobium oxides. Iron, potassium, phosphorus, tantalum, and fluoride were inserted into the TiNb2O7 synthesis process from ultrapure solutions. The mixed oxides obtained were subjected to characterizations by the X-ray diffraction technique, scanning electron microscopy and finally, applied to lithium-ion batteries to evaluate the influence on the electrochemical performance. The results showed that, despite the impact on the formation of the compound TiNb2O7, the presence of iron up to 2,000 ppm in the synthesis was not harmful to the process in general, while the presence of phosphorus and potassium resulted in serious problems in the electrode preparation steps. On the other hand, the presence of tantalum promoted important increases in battery performance, attributed to the formation of high purity mixed oxides (TiNb2O7 and TiTa2O7).

Confined intercalating sulfonated graphene quantum dots into GO laminates for fast alkali recovery

Graphene oxide (GO) membranes with uniform sub-nanometer interlayer channels have shown great promise in the ion sieving field. However, the lack of ion-transporting sites on the GO nanosheets usually leads to inferior ion permeation and selectivity. Although the intercalation of molecules with ionic groups into GO laminates is easily achieved to incorporate ion exchange sites, this approach inevitably enlarges the interlayer spacing, reducing the ionic sieving capacity. Thus, current methods are limited in breaking the permeation and selectivity “trade-off”. Herein, we report a confined intercalation strategy to inject ample sulfonic acid groups into GO laminates using sulfonated graphene quantum dots (SGQD) as intercalators. SGQD with abundant ion exchange sites assembles on the sp2 domains of GO via π-π interactions and confers the GO membranes with continuous ion conduction pathways. Meanwhile, benefiting from the ultra-small size SGQD as well as its sheet morphology, it can well accommodate in the GO laminates. This strategy fulfills the incorporation of ionic sites without expanding channel width and destructing the two-dimensional (2D) regularity for GO laminates, resulting in simultaneous improvements in ion permeability and selectivity. Correspondingly, the resulting membranes show synergistically improving OH- dialysis coefficients of 3.5 × 10−3-8.2 × 10−3 m h−1 and OH-/WO42- separation factors of 56–116 compared with the GO membrane (0.9 × 10−3 m h−1 and 8.4) for separating simulated NaOH/Na2WO4 alkaline effluents. We believe the confined intercalating regulation can act as a versatile and fine way to modify 2D membranes for intensifying ion separation.

Anode Boundary Layer Extraction Strategy for H+–OH– Separation in Undivided Electrolytic Cell: Modeling, Electrochemical Analysis, and Water Softening Application

To promote the application of the electrolysis process for in situ pH adjustment of wastewaters with complex matrices, a robust, industrially scalable, and undivided electrolytic cell featuring the abstraction of H+ from the anode boundary layer was developed in this study, where a tubular Ti porous membrane was used as the anode. Modeling, electrochemical analysis, and COMSOL simulation results show that abstracting H+ from the anode boundary layer could effectively inhibit the transfer of H+ into the bulk solution with the decrease in the anode double-layer thickness and electric double-layer capacitance. Increasing the current density from 6 to 22 mA cm–2 and the influent rate from 330 to 11,100 mL min–1 deteriorated the H+–OH– separation performance, owing to the enhanced electro-migration of H+ into the bulk solution and turbulence state near the anode surface, respectively. The H+–OH– separation performance showed a volcanic type change trend with the acid extraction rate with the optimal value at 50 mL min–1, specifically the separation efficiency of 10%–72% and 16%–94% for H+ and OH– in the acidic and alkaline effluents, respectively, at an influent rate of 500 mL min–1 and a current density of 6–22 mA cm–2. Importantly, the present undivided electrolytic cell showed better H+–OH– separation performance than that of the widely studied membrane-based divided system. The feasibility of this undivided electrolytic cell was also validated by water softening experiments, where the Ca hardness removal efficiency was 42%–92% with energy consumption of 1.2–4.6 kWh (kgCaCO3)−1 at a current density of 6–22 mA cm–2. In general, this new undivided electrolytic cell opened a new pathway for in situ electrochemically regulating wastewater pH.

Malachite green dye purification from effluent using synthesized ceramic clay: Characterisation; optimization and scale up

The rise of industry is crucial to any nation's progress. Pollution levels increased as industrialization expanded, enhancing the necessity to adopt environmental practices. The purpose of this research is to treat the Malachite Green Dye (dye-containing) wastewater with locally available ceramic clay. The ceramic clay was characterized by x-ray diffraction, scanning electron microscopy, thermal analysis, and Fourier transform of infrared and found to be suitable for bioadsorption. Various operating parameters, such as effluent alkalinity and initial dye concentrations; adsorbent size; mass loading; working temperature; experimental time, agitation, and ionic strength, were optimized to treat the effluent up to the recycling limit. The results show that the best conditions for achieving 99.6% dye concentration were an initial pH of 4, a particle size of 2.5 mm, agitations of 210 rpm, a temperature of 35 °C, dosing of 6 g/L, a dye concentration of 50 mg/L, a time of 300 min, and an ionic strength of 0.5 mM. The order of kinetics, isotherms, and thermodynamic studies supported the research findings. In the majority of cases, ceramic clay may be used as a dye remover, which is an exciting benefit for the environment.

Robust electrolysis system divided by bipolar electrode and non-conductive membrane for energy-efficient calcium hardness removal

In this study, an energy-efficient divided bipolar electrolysis system was developed for water softening, where two PTFE membranes were used as the separating materials and a bipolar electrode was employed to enhance the H2O-splitting reactions. As compared with other two operation modes, the optimum calcium harness removal efficiencies of 85% and 57% could be reached in the induction cathode effluent and terminal effluent, respectively, at 8 mA cm−2 in the mode A. Increasing the current density from 5 to 20 mA cm−2 evidently promoted the removal of calcium hardness from 33% to 65% in the terminal effluent and the CaCO3 precipitation rate from 743 to 1462 gCaCO3 h−1 m−2 with the increased energy consumption from 0.53 to 2.2 kWh kg−1CaCO3. The optimized Ca2+/HCO3− molar ratio was 1:1.2 for the calcium hardness removal. In addition, increasing the flow rate into each cathode chamber from 10 to 40 mL min−1 gradually decreased from 67% to 35%. The calcium hardness was mainly removed in the forms of vaterite and calcite in the alkaline effluents and was marginally precipitated as aragonite and calcite on the cathodes surface. Generally, present energy-efficient electrochemical water softening system showed great potential for application in industrial processes.

An integrated electrolysis-microfiltration-ion exchange closed-loop system for effective water softening without chemicals input and spent regenerant discharge

In this study, an energy-efficient and industrially scalable undivided electrolysis cell featuring the abstraction of H+ from the anode boundary layer was developed to produce acid and alkaline effluents. Then, the electrolysis cell was integrated with microfiltration and ion-exchange (IEMI) for water softening. In this system, CaCO3 crystals could form in the alkaline effluent from the electrolysis cell and then was intercepted by a porous tubular Ti microfilter in the crystallizer, and weak acid ion-exchange resin in H+-form (WAC-H) was used to further remove the hardness content residual in water. The closed-loop operation mode of the IEMI system with zero discharge of spent regenerant could be realized by using the acid effluent abstracted from the electrolysis cell to regenerate the exhausted WAC-H and then introducing the spent regenerant into the feed water for hardness precipitation again in the IEMI system. Specifically, the total hardness could reduce from 400 to 40 mg CaCO3 L−1 with a removal efficiency of 90 % at energy consumption of 1.9 kWh (kg CaCO3)−1 when an optimal current density of 10 mA cm−2 was applied. Overall, the developed IEMI system paved the ground for scaling up the applications of the electrochemical softening technology in various industrial and domestic fields.

Deciphering the alkaline stable mechanism of bacterial laccase from Bacillus pumilus by molecular dynamics simulation can improve the decolorization of textile dyes.

Laccases are considered promising tools for removing synthetic dyes from textile and tannery effluents. However, the alkaline pH in the effluents causes laccase instability, inactivation, and difficulty in its bioremediation. Based on a Bacillus pumilus ZB1 (BpLac) derived alkaline stable laccase, this study aimed to elucidate its alkaline stable mechanism at molecular level using molecular dynamics simulation. The effects of metal ions, organic solvents, and inhibitors on BpLac activity were assessed. BpLac formed more salt bridges and negatively charged surface in alkaline environment. Thereafter, pH-induced conformation changes were analyzed using GROMACS at pH 5.0 and 10.0. Among the identified residues with high fluctuation, the distance between Pro359 and Thr414 was stable at pH 10.0 but highly variable at pH 5.0. DSSP analysis suggested that BpLac formed more β-sheet and less coil at pH 10.0. Principal component analysis and free energy landscape indicated that irregular coils formed at pH 5.0 benefit for activity, while rigid α-helix and β-sheet structures formed at pH 10.0 contributed to alkaline stability. Breaking the α-helix near T1 copper center would not reduce alkaline stability but could improve dye decolorization by BpLac. Overall, these findings would advance the potential application of bacterial laccase in alkaline effluent treatment.

Diagnosis, Treatment, and Prevention of Ileostomy Complications: An Updated Review.

An ileostomy is associated with multiple complications that may frequently or persistently affect the life of ostomates. All healthcare professionals should have knowledge of the diagnosis, treatment, and prevention of ileostomy complications. Peristomal dermatitis is caused by watery and highly alkaline effluent. Skin protective products are typically used for local treatment. Ischemia/necrosis occurs due to insufficient arterial blood supply. Retraction is seen in patients with a bulky mesentery and occurs following ischemia. Convex stoma appliances can be used for skin protection against fecal leakage. Small bowel obstruction (SBO) is common and occurs only at the stoma site. Trans-stomal decompression is most effective in these cases. High output stoma (HOS) is defined as a condition when the output exceeds 1,000- 2,000 ml/day, lasting for one to three days. Treatment includes intravenous fluid and electrolyte resuscitation followed by restriction of hypotonic fluid and the use of antimotility (and antisecretory) drugs. Stomal prolapse is a full-thickness protrusion of an inverted bowel. Manual reduction is attempted initially, whereas emergency bowel resection may be needed for incarcerated cases. A parastomal hernia (PSH) is an incisional hernia of the stoma site. Surgery is considered in cases of incarceration, but most cases are manageable with non-surgical treatment.

Effects of ecological roofs in water quality: an experimental study over a humid tropical climate

Although ecological roofs (vegetated or non-vegetated) provide many benefits, it can also leach substances such as nutrients and metals that can affect downstream aquatic ecosystems. Therefore, this work aims to investigate the rainwater quality from ecological roofs in Recife, located in the Northeast Brazil, using local species in a tropical and humid climate. Using four test cells of 1 m2 (one non-vegetated filled with expanded clay aggregate, two vegetated with cactus “Coroa-de-Frade” and grass “Grama Esmeralda”, and one control roof), we analyzed thirteen water quality variables regarding irrigation parameters: pH, electrical conductivity, turbidity, nitrate, ammonia, phosphate, bicarbonate, carbonate, calcium, magnesium, sulfate, potassium, boron, sodium, and sodium adsorption ratio. We simulated rain events controlling its intensity and analyzed a sample of natural rainwater event. All roofs neutralized the pH. Control and clay roofs were source of bicarbonate and calcium, responsible for more alkaline effluents. Carbonate and ammonia were below the recommended limits for irrigation purposes for all roofs. Green roofs were source of nitrate, ammonia, and boron. Neither roofs were source or sink for sulfate and chloride for all analyzed samples. Regarding the natural rainwater experiment, only green roof with Coroa-de-Frade exceeded the recommend irrigation parameters for potassium and phosphate. A post-treatment is required for irrigation purposes. We recommend a first-flush system followed by a filter with sand and activated carbon.

Efficient and green water softening by integrating electrochemically accelerated precipitation and microfiltration with membrane cleaning by periodically anodic polarization

• An efficient and reagent-free EAPS-MF system was developed for water softening. • A hydrophilic PTFE membrane was used as the separation medium in electrolysis cell. • The Ti microfilter with membrane cleaning by anodic polarization was used for CaCO 3 interception. • CaCO 3 precipitation rate was 349 g h −1 m −2 at 100 A m −2 with energy consumption of 1.88 kWh kg −1 . Although the electrochemical water softening in the divided cell has been proven capable of avoiding the requirement of high working electrode surface area, its industrial application is seriously constrained by the fouling of the ion exchange membrane and the lack of an environmentally friendly liquid–solid separation method. In this study, an energy-efficient and reagent-free electrochemically accelerated precipitation and microfiltration combined system (EAPS-MF) was developed for water softening. In typical operation mode A, the electrolysis cell divided by a polytetrafluoroethylene microfiltration membrane (PMM), allowing for the simultaneous production of alkaline and acidic effluents. The alkaline effluent was fed directly into the crystallizer for the formation of CaCO 3 crystals, which were intercepted by a Ti tubular microfilter. The filtrate was then blended with acidic effluent to further reduce water scaling potential by removing the residual alkalinity. In this system, the precipitation rate raised from 97.5 to 348.8 gCaCO 3 h −1 m −2 by elevating current density from 20 to 100 A m −2 , accompanying the increased specific energy consumption from 0.68 to 1.88 kWh (kgCaCO 3 ) −1 or from 0.044 to 0.44 kWh m −3 water treated. The Ti tubular membrane fouling was mainly caused by the accumulation of CaCO 3 cake on its surface, which existed in the predominant type of calcite and marginal type of vaterite. Interestingly, the fouled Ti tubular membrane could be recovered completely within 5 min just by periodically anodic polarization at a current density of 200 A m −2 without production of wasted cleaning brine. Generally, the established EAPS-MF system exhibited significant prospects in promoting the applications of the electrochemical softening process in diverse industrial areas.

Effect of biostimulation in the bioremediation of waters coming from debittering olives process

• The bioremediation of lye waters is accelerated using biostimulation. • Contamination indicators were reduced by native microorganisms in aerated lye waters. • The decrease in pH was compatible with the possible degradation of organic matter. • Biostimulation is an environmentally friendly solution to reduce pollution. The potential bioremediation of native microorganisms presents in lye waters, produced during the industrial debittering of green table olives was studied in this work. Two treatments, T1 and T2, as well as the corresponding control were carried out, whilst the biostimulation method was evaluated under aerobic conditions. The evolution of parameters such as BOD 5 , COD, electrical conductivity and reducing sugars were measured, whereas the growth of native microorganisms was monitored by total plate count. COD parameter showed a decrease of 100% for both treatments, although electrical conductivity decreased around 35-30% in treatment T1 and 19-30 % in the treatment T2. The initial BOD 5 decreased consistently with the reduction in COD. The controls only had aeration, however in absence of biostimulation, similar results were observed in all treatments, due to the growth of microorganisms stimulated by the native source of organic matter. However, biostimulation accelerated the process, especially in the reduction of pH, transforming the alkaline effluent into a more neutral effluent.

Ultrafiltration and reuse opportunities of sectorial effluents from a kraft pulp mill in Brazil

Abstract The pulp industry is a high natural resources consumer and has a large polluting potential. The pulping sector with the most effluent generation is the bleaching plant. Based on the need of water consumption reduction, this research aimed to evaluate the treatment of the alkaline effluent from an EP-stage bleaching plant and the white water from drying machine using ultrafiltration membranes in order to enable the reuse of the permeate in the process. An ultrafiltration pilot plant was used. Laboratory analyses were performed for the feed, permeate and retentate. Flux and transmembrane pressure (TMP) data were obtained from the pilot plant database. There were an average color and COD removals of 38 % and 39 %, respectively, for the EP-effluent and 58 % and 67 %, respectively for the white water; and a high turbidity and TSS removal (above 98 %) for both effluents. Substantial metals removal such as sodium, potassium, calcium, iron, magnesium and manganese was achieved. Some possibilities to reuse were considered: return to the water treatment plant, cooling of the digester bottom, equipment cooling, reuse in evaporation surface condensers. The use of ultrafiltration for the treatment of the alkaline effluent from the bleaching EP-stage and white water can be an interesting option.