Initial Chemical Oxygen Demand Concentration Research Articles

Fe-zeolite catalyst for ozonation of pulp and paper wastewater for sustainable water resources

The pulp and paper industry consumes enormous quality of freshwater, leading to wastewater. It must be treated to remove pollutants, particularly residual dyestuffs, before releasing them to water bodies to avoid adverse environmental effects. The traditional wastewater treatment methods used for the pulp and paper industry are less efficient in colour and chemical oxygen demand (COD) removal. The current study is aimed at developing a novel catalyst for the catalytic ozonation of pulp and paper wastewater with better colour and COD removal for sustainable resources of clean water. The proposed catalyst is impregnated by iron on natural zeolites. Various parameters such as catalyst dose, pH, ozone dose, initial COD concentration, and reaction time are studied and optimized. The performance was evaluated by comparing the results with the single ozonation process (SOP) and catalytic ozonation process (COP). The highest COD and colour reduction efficiencies have been achieved, i.e., 71%, and 88% at a natural pH of 6.8. The proposed process achieved higher COD and colour efficiencies than the single ozonation process and catalytic ozonation process using raw zeolites. The improvement in efficiencies are 23% and 29% for SOP and 17% and 19% for COP, respectively. Hence, the results proposed the sustainability and applicability of COP to treat paper and pulp sector effluent.

Response Surface Methodology Optimization of Chemical Oxygen Demand Removal by Rice Husk Activated Carbon

High Chemical Oxygen Demand (COD) levels in water indicate a vast amount of oxidizable matter that consumes a lot of dissolved oxygen in water. This results in adverse impacts on both aquatic ecosystems and human health. Wastewater from the fish cracker industry typically has high organic content and high COD value. In this study, rice husk was chosen as the raw material because of its abundance and economy. The optimum adsorption parameters such as flow rate, contact time, and initial COD concentration that affect adsorption by rice husk activated carbon were studied using Response Surface Methodology. The treatment was done in a continuous fixed-bed column. From the Box-Behnken design, it was determined that 68.09% removal percentage resulted from the best combination of 4.5 hours of contact time, 1 mL/min of flowrate, and 5% initial COD concentration. The SEM micrograph shows the adsorbent consists of a large number of pores before adsorption. Based on the study, rice husk activated carbon can be an alternative treatment for COD removal in wastewater. The use of activated carbon derived from agricultural waste materials can help reduce the waste produced, which will otherwise end up in the landfill.

Photocatalytic Degradation of Sugarcane Vinasse Using ZnO Photocatalyst: Operating Parameters, Kinetic Studies, Phytotoxicity Assessments, and Reusability.

Photocatalytic degradation performance is highly related to optimized operating parameters such as initial concentration, pH value, and catalyst dosage. In this study, the impact of various parameters on the photocatalytic degradation of anaerobically digested vinasse (AnVE) has been determined through decolourization and chemical oxygen demand (COD) reduction efficiency using zinc oxide (ZnO) photocatalyst. In this context, the application of photocatalytic degradation in treating sugarcane vinasse using ZnO is yet to be explored. The COD reduction efficiency and decolourization achieved 83.40% and 99.29%, respectively, under the conditions of 250 mg/L initial COD concentration, pH 10, and 2.0 g/L catalyst dosage. The phytotoxicity assessment was also conducted to determine the toxicity of AnVE before and after treatment using mung bean (Vigna radiata). The reduction of root length and the weight of mung bean indicated that the sugarcane vinasse contains enormous amounts of organic substances that affect the plant's growth. The toxicity reduction in the AnVE solution can be proved by UV–Vis absorption spectra. Furthermore, the catalyst recovery achieved 93% in the reusability test. However, the COD reduction efficiency and decolourization were reduced every cycle. It was due to the depletion of the active sites in the catalyst with the adsorption of organic molecules. Thus, it can be concluded that the photocatalytic degradation in the treatment of AnVE was effective in organic degradation, decolorization, toxicity reduction and can be reused after the recovery process.Graphical abstract

Adsorptive removal of dairy industrial pollutants by chitosan zinc –oxide nanoadsorbent- A comparitive study of artificial neural network and quadratic Box-Behnken design

Aim: To investigate the effect of operational parameters on the adsorption of biological oxygen demand (BOD) and chemical oxygen demand (COD) on to Chitosan zinc oxide (CZnO) nanoadsorbent using cost-effective and eco-friendly nanoadsorbent based effluent treatment processes. Methodology: CZnO nanoadsorbent particle was synthesized using chemical precipitation method. The nano size <100 nm was achieved using high-speed cryo all mill, followed by the characterization using high-end instruments such as scanning electron microscope with elemental detection sensor (SEM-EDS), atomic force microscope (AFM), X-ray diffractometer (XRD) and Fourier transform inform infrared spectroscopy (FT-IR). Modeling and optimization of operational parameters were done with the artificial neural network (ANN) and Box-BehnkenDesign (BBD) statistical tools. Results: Optimized treatment combination for adsorption of BOD and COD were found at initial BOD and COD concentration of 100 and 200 mg l−1, pH of 7.0 and 2.0, adsorbent dosage of 1.25 mg l−1, contact time of 100 and 60 min. In these conditionsthe desirability values of 0.988 and 0.950 were found for BOD and COD adsorption. The maximum per cent reduction of BOD and COD by using CZnO nanoadsorbent was found to be 96.71 and 87.56. Two models such as Quadratic Box-Behnken and ANN were compared in term of sum of square errors (SSE), root mean square error (RMSE) and correlation coefficient (R2) values. Interpretation: The results obtained revel the well trained ANN model found to be more accurate in prediction of BOD and COD adsorption process parameters compared to BBD model.

Hydrogen peroxide assisted electrocoagulation treatment of rice gain based biodigester effluent: mechanism, performance, and cost analysis

Abstract In the current scenario treatment of industrial waste water is big challenge especially waste water that contain high organic load. Hydrogen peroxide assisted electrocoagulation (EC) process provides better result to treat highly polluted wastewater as compared to EC alone. However, hydrogen peroxide is well known as a strong oxidant, which cast a potential threat to human health. To overcome this problem hydrogen peroxide has been used here for treatment of wastewater in small quantity, and that consume during the process. Therefore the harmful effect of hydrogen peroxide in human and aquatic life could be minimized. This work is an attempt to treat biodigester effluent (BDE) using H2O2 assisted EC processes with respect to chemical oxygen demand (COD) and color reductions. To perform this experiment both iron and aluminum electrodes are used as an electrode material in the presence of H2O2. In case of iron electrode the maximum COD and color reduction efficiency of 98.3 and 83.6% was achieved at the cost of 1.5 Wh/dm3 energy consumption while maximum COD and color removal efficiency of 96.8 and 77.1% with 1.7 Wh/dm3 of energy consumption was observed in the aluminum electrode based EC process. A part from this conventional biological process (i.e., activated sludge treatment, ponds, and lagoon etc.) and physiochemical treatment process (i.e., coagulation, adsorption) provided treatment efficiency of 40–80% hence hydrogen peroxide assisted EC process should a better choice to treat distillery effluent. Furthermore, hybrid EC process was also performed with iron used as anode and aluminum as cathode in the presence of H2O2. Iron electrode based peroxi-EC process provided better result at optimum operating conditions; current density of 114 A/m2, initial COD concentration of 12,000 mg/dm3, initial pH of 7.3, H2O2 concentration of 120 mg/dm3, stirring speed of 120 rpm and electrolysis time of 90 min. The cost estimated for operation is 1.56 US $/m3. Finally, sludge analysis and cost optimization are also incorporated in this article.

The Effect of Initial Conditions with Aerobic Biological Treatment on Aniline Dyeing Wastewater

According to the characteristics of aniline dyeing wastewater, aerobic biological treatment was adopted herein, and high-throughput sequencing technology was used to analyze the changes to the microbial community structure and diversity in the aerobic sludge acclimation stage. As a result, according to the experimental study on the effects of different biomass, the initial pH value and the salinity with the aerobic biological treatment, the chemical oxygen demand (COD) degradation rate can increase linearly with the increase in biomass under different biomass conditions. The organic matter degradation rate is 6.24 mg/L COD·h−1·(mg/L·MLSS)−1, with a correlation coefficient (R2) of 0.98704. When the initial pH value is less than 7.0 ± 0.2, the COD degradation rate increases with the increase in the initial pH value and then decreases gradually. The optimal sludge concentration is 4 g/L; the optimal initial pH value is in the range of 7.0–8.0; the optimal salinity is 1.7%. When the initial concentration of COD is 3000 mg/L, the COD value gradually stabilizes and decreases to 1500 mg/L after 32 h, the degradation rate reaches 50%, and the pH decreases from 7.5 to 4.5. Sphingopyxis has been detected in sludge samples from the third cycle of acclimation, which can biodegrade aromatic compounds, anthraquinone dyes, and their intermediates, and the relative abundance of Sphingopyxis increased from 0.18% to 5.08%, indicating a potential biodegradation ability of aniline dyeing wastewater.

Competence of Lepironia articulata in eradicating chemical oxygen demand and ammoniacal nitrogen in coffee processing mill effluent and its potential as green straw

Phytoremediation is an environmentally friendly technique in wastewater treatment because of its sustainability, cost-effectiveness, and simplicity. This study was conducted to examine the feasibility of use of Lepironia articulata, a potential phytoremediation plant that is native to Malaysia, in remediating coffee processing mill effluent (CPME). The aim was to determine effluent concentration or contaminant load that the plant can resist, while simultaneously results in the good removal of pollutants during phytoremediation. Four brushes of L. articulata were planted individually in a pail/reactor (mentioned as reactor afterward) containing 3 kg of sand and exposed to five different concentrations of CPME (0%, 30%, 50%, 75%, and 100%). The initial chemical oxygen demand (COD) values were 510, 3100, 4200, 7290, and 8470 mg/L, respectively, and ammoniacal nitrogen (AN) concentrations were 26, 128, 225, 376, and 509 mg/L, respectively. The height, appearance, and efficiency in removing COD and AN of each plant was observed throughout the 35-day exposure period. Results showed that plants exposed to 75% CPME demonstrated better growth than those exposed to other concentrations and exhibited the highest COD and AN removal rates (85.0% and 84.0%, respectively), providing evidence that L. articulata can be used as a phytoremediation agent of CPME with an initial COD concentration of 7290 mg/L and AN concentration of 376 mg/L. This study highlights its support to the Sustainable Development Goals adopted by the United Nations, particularly the reclamation of plant biomass used as a treatment agent and conversion into biodegradable straws. Moreover, this study adds an attractive additional point of transforming waste into resource with the proposed wastewater treatment technology.

Effect of Electrode Material on the Removal of Industrial Oil and Soap Wastewater Using Electrocoagulation Process

Treatment of oil and soap industrial wastewater using aluminum and iron electrode material has been investigated in this study to compare for each electrode, the performance of the electrocoagulation process. The effectiveness of relevant industrial wastewater characteristics such as the chemical oxygen demand (COD) and oil-grease removal effects of major operating parameters such as medium pH value, electrode material, and current density, and running time and energy consumption were studied. All experiments were done in an electrocoagulation cell with an effective volume of 500 mg/ liters. Under the same operating conditions, it was observed that aluminum electrodes have higher efficiency of removal than iron electrodes. COD and O&G removal efficiencies of 94.93%, 90.20% and 27.49%, 13.27% were observed for aluminum and iron electrode in a special case with optimum initial pH value, maximum current density, time, and initial COD concentration equal to 3, 73.33 A/m2, 30 min, 19750 mg/l, respectively. The electrode energy consumptions for each electrode material have been calculated to be 1.68, 3.04 KWh/kg COD for Aluminum and iron respectively at 15 volts. It can be concluded that the electrocoagulation process using aluminum electrodes is efficient for COD and O&G removal from industrial wastewater

Adsorption of COD in wastewater by Activated Carbon from Rice Husk

Organic pollution occurs due to the presence of organic compound that will causing oxygen depletion and gives potential adverse impacts on human health and the environment. Wastewater from the fish cracker industry typically has high chemical oxygen demand (COD) and it is needed to be treated before release to water bodies in order to reduce the organic pollution. The treatment of COD was done using rice husk activated carbon (RHAC) that produced from agricultural wastes that contributed to waste minimization and reduce the environmental pollution. Therefore, this study emphasized on the feasibility of rice husk activated carbon for removing the COD from fish cracker wastewater. It was also to identify the optimization factors (pH, flow rate and initial concentration of COD) that affecting adsorption by rice husk activated carbon. RHAC was produced by chemical activation using phosphoric acid, H3PO4 and a real wastewater from fish cracker industry was collected, characterized, and treated by using continuous fixed bed column adsorption method. The result shows that the adsorption of COD by RHAC was optimum at pH 2, flow rate 5 ml/min and 5 % v/v initial COD concentration with the COD removal at 31.8% (150 mg/L) which comply with Standard B. Thus, RHAC could be used to develop an alternative method and suitable carbonaceous substances that was used to treat water and wastewater.

Valorization of refinery wastewater for lipid-rich biomass production by Rhodococcus opacus in batch system: A kinetic approach

This study investigated utilization of refinery wastewater containing complex hydrocarbons as the sole substrate for lipid-rich biomass production by Rhodococcus opacus in batch system followed by its kinetic modeling. The effect of different initial chemical oxygen demand (COD) concentrations of the wastewater in the range 2.5–4.5 g L−1 was examined on biomass growth, COD utilization and lipid production by R. opacus. Almost complete utilization (96.8%) of COD present in the wastewater was achieved for an initial COD concentration of 2.5 g L−1 and the value decreased to 90% and 75% for 3.5 g L−1and 4.5 g L−1COD concentrations, respectively. Moreover, a maximum lipid production of 1.3 g L−1 was obtained for an initial COD concentration of 3.5 g L−1. The results of COD utilization by the bacterium were further fitted to substrate utilization kinetic models reported in the literature, which matched well with the Logistic model. Modified Gompertz model best fitted the kinetic data on biomass growth and lipid production by the bacterium. Whereas R. opacus biomass specific growth was found to be inhibited at a high COD concentration of the wastewater, Haldane model predicted the experimental specific growth rate values with a very high determination of coefficient (R2) value of more than 0.99. All these results suggest that refinery wastewater can serve as the sole substrate for lipid-rich biomass production by R. opacus, thereby adding value to the wastewater treatment process.

A new activated carbon prepared from cypress cones and its application in the COD reduction and colour removal from industrial textile effluent

A new activated carbon from local cypress cones (CCAC) was prepared using phosphoric acid as a chemical activating agent. It presented a Brunauer, Emmett and Teller surface area (SBET) equal to 379.5117 ± 2.3509 m2 g−1 with an amorphous nature. Scanning electron microscopy analysis revealed a heterogeneous and random shape of pores. The reduction in colour and chemical oxygen demand (COD) from the industrial aqueous effluent from the textile company “COTITEX” was the principal performance study of the resulting material. The kinetic data of the adsorption process obeyed a pseudo-second-order model with R2 of 0.988. From five studied parameters, only the initial COD concentration, the pH and the temperature influenced the COD reduction at equilibrium. Maximum COD and colour removal, respectively, 19% and 80.4% were recorded under optimal adsorption conditions of 2 g L−1 of the adsorbent amount, 323°K of operating temperature, pH = 11 and a stirring speed = 300 rpm. The present study showed that CCAC could be a proper material for coloured effluent treatment, whereas, for a better COD reduction, pretreatment is required.

Enhanced treatment of landfill leachate wastewater using sono(US)-ozone(O3)–electrocoagulation(EC) process: role of process parameters on color, COD and electrical energy consumption

The combination of advanced oxidation processes (AOPs) and electrochemical process is gaining growing popularity for use in wastewater treatment. The present work explores for the first time, treatment of leachate wastewater from landfill waste using a combination of sonication (US), ozonation (O3) and electrocoagulation (EC) process expressed by % color removal, % Chemical Oxygen Demand (COD) removal and its associated electrical energy consumption. The results revealed that, the combined process (US/O3/EC) is highly successful in the treatment of leachate wastewater from landfill in terms of % color removal (100 %) and % COD removal (97.50 %) with low electrical energy consumption (8kWhr/m3) than the other hybrid and single process such as O3/EC, US/EC, US/O3 and EC, O3, US. The influence of different process parameters such as electrolyte concentration (1.50–7.50 g/L), current density (1.25–7.50 A/dm2), initial effluent pH (2–11), COD concentration (2000–6000 ppm), O3 production (0.75–3.75 g/hr) and sonication power (20–100 Watts) were studied on the efficiency of pollutant removal evaluated by reduction of % color and % COD and electrical energy consumption using hybrid US/O3/EC process. Overall, the analysis clearly showed that the approaches to integrated treatment technologies could synergistically remove the pollutant from the wastewater.

Esparto paper industry wastewater treatment by adsorption onto powdered activated carbon

ABSTRACT The discharge of Esparto paper industrial wastewater (EPIW) of SNCPA Company of Kasserine – Tunisia in nature without any treatment can cause harmful effects to the environment. To reduce this danger, several treatment processes have been implemented, in particular, the adsorption technique. The present original study consists of using powdered activated carbon (PAC) to treat EPIW. The tests were carried out on different chemical oxygen demand (COD) concentration of EPIW ranging from 2 to 20 g/L. The influence of initial COD concentration, adsorbent dose, pH and contact time were investigated at temperature of 25 ± 2°C. The equilibrium results were modelled and assessed via Freundlich, Langmuir, Temkin and Dubunin–Radushkevich isotherms models. The error analysis was evaluated by three error functions: the average relative error deviation, the Marquardt’s percent standard error deviation and the Sum of the squares of the errors. The results showed that COD removal efficiency, maximum adsorption capacity and colour removal rate were 94%, 190 mg/g and 90%, respectively, for pH = 6, an adsorbent dose of 75 g/L, initial COD concentration of 9.3 g/L and contact time of 60 min. Besides, the main characteristics values of treated EPIW (BOD, TCOD, pH and Salinity) at natural conditions were 200 ± 30 mg O2/L, 1300 ± 50 mg O2/L, 7.2 ± 0.1 and 1.7 g/L ± 0.1, respectively, which were below the ISO-14,000 standards conditions for release in public sewerage system. Furthermore, both the higher value of correlation coefficients (R2) and the lower value of SSE have shown that Freundlich model provided the best fits to adsorption experimental results.

Application of Fenton pre-oxidation, Ca-induced coagulation, and sludge reclamation for enhanced treatment of ultra-high concentration poly(vinyl alcohol) wastewater

Poly(vinyl alcohol) (PVA) wastewater contains up to 10,000 mg/L dissolved organic carbon. A concentration of this magnitude results in a high chemical oxygen demand (COD), which generates major problems for industrial wastewater treatment in general, and the textile and chemical industries, in particular. Thus, we propose a two-stage treatment process that uses Fenton pre-oxidation, coupled with Ca-induced coagulation, to reduce the PVA and COD wastewater concentration. The optimal concentrations of FeSO4 and CaCl2 per gram of PVA were 0.8 g/g-PVA and 4.0 g/g-PVA, respectively, which is significantly lower than that of other reported treatments. Due to successful oxidation, the long chains of PVA molecules were broken up and the OH groups were partially oxidized to COOH. During the coagulation stage, Ca2+ was able to efficiently bind with the PVA pre-oxidation products, thereby forming insoluble compounds. Given initial COD and PVA concentrations of 20,450 and 10,000 mg/L, respectively, a maximum of 81.3 % COD and 96.0 % PVA was removed following this two-stage procedure. Furthermore, the sludge residue was used to remove Sb(III) from the wastewater, achieving an Sb(III) adsorption capacity of 16.0 mg/g. Thus, this study provides new insight into affordable and effective treatment of high concentration PVA-containing wastewater.

Effects of chemical oxygen demand concentration, pH and operation cycle on polyhydroxyalkanoates synthesis with waste sludge

ABSTRACT To reduce the cost of polyhydroxyalkanoate (PHA) production and dispose the amount of waste sludge simultaneously, chemical oxygen demand (COD) concentration, pH and operation cycle were investigated to find the optimal PHA synthesis conditions with waste sludge in this study. The maximum PHA content (31.3% of the cell dry weight (CDW)), as well as the highest PHA conversion rate (0.30 mg COD/mg COD) and PHA-specific synthesis rate (6.12 mg COD/mg CDW·h), was achieved with initial COD concentration, pH value and operation cycle: 6000 mg/L, 8.5 and 24 h. In order to further investigate the process of PHA synthesis, COD removal rate and CDW were also introduced. This study could provide valuable information for increasing the production of PHA with waste sludge.

Optimal conditions for olive mill wastewater treatment using ultrasound and advanced oxidation processes

The treatment of olive mill wastewater (OMW) in Jordan was investigated in this work using ultrasound oxidation (sonolysis) combined with other advanced oxidation processes such as ultraviolet radiation, hydrogen peroxide (H2O2) and titanium oxide (TiO2) catalyst. The efficiency of the combined oxidation process was evaluated based on the changes in the chemical oxygen demand (COD). The results showed that 59% COD removal was achieved within 90 min in the ultrasound /UV/TiO2 system. A more significant synergistic effect was observed on the COD removal efficiency when a combination of US/UV/TiO2 (sonophotocatalytic) processes was used at low ultrasound frequency. The results were then compared with the COD values obtained when each of these processes was used individually. The effects of different operating conditions such as, ultrasound power, initial COD concentration, the concentration of TiO2, frequency of ultrasound, and temperature on the OMW oxidation efficiency were studied and evaluated. The effect of adding a radical scavenger (sodium carbonate) on the OMW oxidation efficiency was investigated. The results showed that the sonophotocatalytic oxidation of OMW was affected by the initial COD, acoustic power, temperature and TiO2 concentration. The sonophotocatalytic oxidation of OMW increased with increasing the ultrasound power, temperature and H2O2 concentration. Sonolysis at frequency of 40 kHz combined with photocatalysis was not observed to have a significant effect on the OMW oxidation compared to sonication at frequency of 20 kHz. It was also found that the OMW oxidation was suppressed by the presence of the radical scavenger. The COD removal efficiency increased slightly with the increase of TiO2 concentration up to certain point due to the formation of oxidizing species. At ultrasound frequency of 20 kHz, considerable COD reduction of OMW was reported, indicating the effectiveness of the combined US/UV/TiO2 process for the OMW treatment.

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.

Three-dimensional electro-Fenton system with iron foam as particle electrode for folic acid wastewater pretreatment

At the very first time, a three-dimensional (3D) iron foam was used as the particle electrode for folic acid (FA) wastewater pretreatment in the electro-Fenton (EF) process. In this work, the effects of key operating parameters, including the initial COD concentration, applied current, initial pH and iron foam dosage were optimized regarding the chemical oxygen demand (COD) and total nitrogen (TN). COD and TN removal percentage of FA wastewater reached 43.5% and 70.4%, respectively during 6 h electrolysis under the following optimal conditions: initial COD concentration of 10,000 mg/L, applied current of 300 mA, initial pH of 3 and iron foam dosage of 4 g. Regarding the main oxidant species in the proposed EF with iron foam particle electrode, OH and active chlorine were responsible for FA mineralization, confirming by the electron paramagnetic resonance (EPR) spectra of DMPO−OH. The kinetic analysis and mechanism study suggested that both electro-oxidation and electro-coagulation exited in the system. A possible FA degradation pathway based on the identification of by-products was proposed according to Liquid chromatography/time-of-flight/mass spectrometry results. In addition, BOD5/COD ratio improved from 0.22 to 0.44 after EF treatment coupled with toxicity reduction. In a word, EF with iron foam particle electrode was a feasible process for FA pretreatment.

Pre-treatment Processes Optimization for the Purification of Olive Mill Wastewater Through a Pilot-scale Membrane Plant

The reported work deals with the evaluation of two different pre-treatment processes performances for the purification of a real olive mill wastewater. The wastewater was from an oil mill placed in the South of Italy and presents high Chemical Oxygen Demand (COD), Total Organic Carbon (TOC) and phenols concentrations, besides other organic pollutants, an acid pH and brown colour. Therefore, this complex wastewater resulted in low- biodegradable and difficult to be treated by a solely process. To this aim, the present work will evaluate optimal operating parameters of coagulation-flocculation and photocatalysis pre-treatments to achieve suitable physical-chemical properties of the effluent, before the membrane treatment in a pilot-scale plant. In detail, the wastewater was firstly treated with an organic coagulant (chitosan) and then a photocatalytic step follows before the more efficient integrated membrane process. After the photocatalytic process, the COD, TOC and Phenols concentrations decreased to up 42 %, 38 % and 36 %, respectively, in comparison with the initial values. Subsequently, a series of four separation processes (ultrafiltration, nanofiltration and reverse osmosis) was performed and almost the total initial COD, TOC and phenols concentrations were removed.

Biorefinery of Dioscorea composita Hemsl with ferric chloride for saponins conversion to diosgenin and recycling the waste to biomethane

Diosgenin is an important raw material for the synthesis of steroid hormone drug and largely required in the pharmaceutical industry. In this study, a novel process for biorefinery of Dioscorea composita Hemsl (DCH) with ferric chloride was developed to investigate the conversion of saponins to diosgenin. Furthermore, the waste, including sugary wastewater and starch residue, as recyclable biomass resources after diosgenin extraction was devoted to biomethane. Consequently, the highest yield of diosgenin (3.02%) was obtained using ethanol/water/petroleum ether (15/16/20, v/v/v) with a total volume of 255 mL containing 80 mL 5.0 g/L ferric chloride aqueous solution at 150 °C for 2 h. The yield extracted with FeCl3 was 16.6% higher than the traditional sulfuric acid hydrolysis method and was even 2.3 times more than the biphasic sulfuric acid hydrolysis method. Similarly, without consuming sulfuric acid, the yield was 79.76% higher than the control method. After fermentation, a maximum biomethane yield of 310.5 mL/g COD (chemical oxygen demand) was achieved from wastewater and the decomposition efficiency reached 91.1% with an initial COD concentration of 10,800 mg/L decreasing to 960 mg/L. The final biomethane productivity of waste residues was 278.8 mL/g VS and the VS degradation efficiency was 95.8% after a week. Therefore, the novel method with FeCl3-catalyzed acidolysis to produce diosgenin and biomethane may be an alternative much cleaner approach to better utilize dioscorea resources.