Combination Of Hydrodynamic Cavitation Research Articles

Synergistic enhancement in hydrodynamic cavitation combined with peroxymonosulfate fenton-like process for bpa degradation: New insights into the role of cavitation bubbles in regulation reaction pathway

The combination of hydrodynamic cavitation (HC) and Fenton-like oxidation technology can dramatically enhance the pollutant removal capacity, however, the synergistic effect of cavitation and catalysts on reactive oxygen species (ROS) generation remained enigmatic. In this study, we established a combined system based on HC and Ce-MnFe2O4 activated peroxymonosulfate (PMS) for BPA removal, and attentions were paid on the role of cavitation bubbles. The results show that the combination of HC in Ce-MnFe2O4 activated PMS could mediate the degradation of BPA from the non-radical pathway dominated by 1O2 to •O2− dominated radical pathway. Both controlled experiments and theoretical calculations revealed that the cavitation bubbles with different sizes play the dominant role in ROS generation. The microjets produced by the collapse of cavitation bubbles could create a large number of oxygen vacancy defects on Ce-MnFe2O4 surface, which modify the activation barrier of PMS and facilitate the generation of •O2− thermodynamically. The stable existing cavitation bubbles with the size of 100∼400 nm could create considerable gas-liquid interface. The molecular dynamics simulations show that the nano bubbles can concentrate the BPA and increase the probability of contacts between BPA and Ce-MnFe2O4, hence effectively solve the issues of short lifetime of •O2− radicals and limited mass transfer distance to strengthen the reaction. In addition, the PMS/Ce-MnFe2O4/HC system not only achieves the satisfied COD (95 %) and TOC (65 %) removal efficiency but also enabled the BPA-contaminated water with a low energy cost of 0.065 kWh·m−3 and oxidant cost, highlighting the application potential of the HC technology for contaminated water.

Combination of hydrodynamic cavitation with CoFe2O4 photocatalyst for activation of peracetic acid under UVC irradiation in synergistic degradation of bisphenol A

This study was aimed at activating peracetic acid (PAA) to degrade bisphenol A (BPA) in aqueous media by combining a system of hydrodynamic cavitation (HC) with CoFe2O4 photocatalyst under UVC irradiation. The CoFe2O4 was successfully synthesized and characterized by various characterization techniques. The influence of various HC approaches alone and combined with photocatalysis on the BPA degradation was explored. After 60 min reaction, the BPA degradation efficiency achieved by CoFe2O4, UV, HC, and PAA individually was 0.69 %, 2.77 %, 6.45 %, and 14.23 %, respectively. At same experimental conditions, under the CoFe2O4 + HC + UV, CoFe2O4 + HC + PAA, CoFe2O4 + UV + PAA and CoFe2O4 + HC + UV + PAA processes, BPA degradation rates were 68.47 %, 77.91 %, 84.23 % and 97.29 %, respectively. The BPA degradation efficiency was examined under various operational parameters, including pH (3−11), BPA concentration (20–40 mg/L), load of CoFe2O4 (0.1–0.4 g/L), PAA dosage (50–200 μmol/L), inlet pressure (1.0–4.0 bar), and reaction time (0–60 min). 97.29 % BPA was degraded over 60 min in the ideal reaction conditions (pH: 7.0, BPA: 20 mg/L, CoFe2O4: 0.4 g/L, PAA: 200 μmol/L, inlet pressure:4.0 bar). BothO·Hradicals and R−O.were contributed to BPA reaction system, andO·Hplayed as the dominant contributor. Overall, CoFe2O4 + HC + UV + PAA system provides a low-energy and low-cost strategy for degrading and mineralizing organic contaminants from waters.

Hydrodynamic cavitation and photocatalysis for effluent treatment: Key operating parameters and synergistic effects

A combination of hydrodynamic cavitation and photocatalysis (HC-PC) is a promising water treatment technology for the removal of recalcitrant pollutants. In this work, we investigated influence of key parameters of this hybrid technology such as initial concentration, catalyst loading, pH, re-circulating flow rate and cavitation device/scale on degradation of three model pollutants (coumarin, paracetamol and dichloroaniline). Unlike previous HC-PC studies, the individual and combined systems were investigated for each parameter to determine their effect on system performance and overall synergy. We report a dependence of logKow for both systems, with highest removal (100% in 20 min with AC-PC, 37% in 120 min, or 350 passes, with HC-PC) and synergy (Synergistic index of 2.8 and 1.2 for AC-PC and HC-PC, respectively) associated with the more hydrophobic compound, dichloroaniline. HC-PC performance increased and synergy decreased with increasing catalyst loading, and the inverse effect was found with initial concentration (C0: 17.5 to 70 ppm). Similarly, pH decreased performance but increased synergy and low re-circulating flow rate increased performance but decreased synergy. Detailed analysis of these results indicated the utilisation of in-situ generated H2O2 from recombined OH radicals is the main contributor of the observed synergy, and not physical interactions between cavities and photocatalyst particles. Following this, for the first time, influence of cavitation device type (based on linear flows and swirling flows) and device scale on overall performance of HC-PC system was quantified. Vortex based cavitation device was found to provide a 20% and 25% higher performance and synergy compared to a linear flow based cavitation device like orifice. The results presented here provide valuable insights into the synergy of HC and photocatalytic systems.

Performance evaluation of hydrodynamic cavitation in combination with AOPs for degradation of tannery wastewater

Tannery wastewater effluent (TWE) consists of a variety of complex structured compounds having very low biodegradability. Few attempts have been made to treat real-time TWE consisting of complex compounds and find the intermediate compounds formed during the HC+PAA+ FeSO4.7 H2O treatment system. Therefore, a pilot scale study has been conducted on an orifice-embedded hydrodynamic cavitation reactor for treating real-time TWE. Liquid chromatography-high resolution mass spectrometry (LC-HRMS) has been carried out to identify the specific compounds present in TWE before and after treatment. Response surface methodology (RSM) – Box-Behnken design (BBD) obtained maximum COD, TDS and turbidity removal efficiency of 72.36%, 94.54% and 98.89%, respectively, at cavitation time-97.5 min, inlet pressure-7.5 bar, pH-2, orifice diameter-0.5 mm, PAA dosage-17.5 g/L, and PAA /FeSO4.7 H2O-2:1 ratio. The reaction rate constant was increased from 2.455 × 10−3 to 12.75 × 10−3 min−1 when AOPs were combined with HC. The study concluded that the degradation using HC+PAA+ FeSO4.7 H2O successfully increased the biodegradability of the TWE without forming any toxic by-products.

Combination of hydrodynamic cavitation with oxidants for efficient treatment of synthetic and real textile wastewater

In this study, the degradation of direct red 89 (DR89) dye from synthetic wastewater was assessed by lab-scaled hydrodynamic cavitation (HC) combined with different oxidants such as periodate (PI), persulfate (PS), and oxalic acid (OA). The degradation tests were carried out by combining the three oxidants in the absence of HC, and using HC with only one of the oxidants (HC/OA, HC/PS, and HC/PI) or with all combined (HC/PS/OA/PI). In all processes, the degradation constants followed first-order reaction kinetics, being the highest one that of the HC/PS/OA/PI process, equal to 2.01 × 10−1 min−1. The degradation of DR89 was affected by pH, initial dye concentration, and reaction time. The degradation efficiency increased when pH decreased obtaining the best results at pH 3.0 due to favorable conditions for the generation and persistence of radical species. The degradation of the dye improved with increasing dose of OA, PS and PI. The best results were achieved using dosages of OA, PS, and PI of 100.0, 125.0, and 150.0 mg L−1, respectively. The quenching experiments revealed the presence of OH, SO4−, IO3, O2–, and 1O2 in the HC/PS/OA/PI process, while OH, SO4− and IO3 were the dominant responsible radicals. The rate constants of the individual processes were used to calculate the value of the synergetic coefficient of HC/PS/OA/PI process. At the optimum conditions, the calculated synergetic coefficient was 15.39. The effectiveness of the HC/PS/OA/PI process in the removal of color and COD from real textile wastewater was also investigated and exhibited the 96.23 ± 1.92 % and 93.84 ± 0.94 % reduction of color and COD after 70 min reaction time, respectively. The results showed that the combined process can be a useful technology for the treatment of textile wastewater.

Synergistic effect of hydrodynamic cavitation and plasma oxidation for the degradation of Rhodamine B dye wastewater

In this study, the degradation of Rhodamine B dye based on the combination of hydrodynamic cavitation (HC) and other advanced oxidation (such as H2O2 and Plasma), which can improve the overall degradation efficiency effectively. According to different operating parameters, such as inlet pressure, concentration and pH value of the solution, the structure parameters of HC and system parameters of plasma device were optimized to obtain the maximum degradation of Rhodamine B. And then, the degradation effects of combination methods of HC, Plasma, HC + Plasma, and HC + H2O2 were investigated experimentally. It was found that Hydrodynamic cavitation and other methods can cause synergistic effect and obtain a higher degradation rate. The maximum degradation rate and synergy indexes are 96.86 % and 2.74, respectively, when the hydrodynamic cavitation was combined with plasma oxidation. Comprehensively considering the degradation rate, synergy index and treatment cost, the combined effect of hydrodynamic cavitation and plasma oxidation has higher degradation efficiency and lower operation cost compared with other combination modes, which is more likely to develop in the direction of large-scale application.

Hydrodynamic cavitation as an efficient water treatment method for various sewage:- A review.

With the development of industry and the rapid growth of population, the current water treatment technologies face many challenges. Hydrodynamic cavitation as a green and efficient means of water treatment has attracted much attention. During the hydrodynamic cavitation, enormous energy could be released into the surrounding liquid which causes thermal effects (local hotspots with 4600 K), mechanical effects (pressures of 1500 bar) and chemical effects (hydroxyl radicals). These conditions can degrade bacteria and organic substance in sewage. Moreover, the combination of hydrodynamic cavitation and other water treatment methods can produce a coupling effect. In this review, we summarize the methods of hydrodynamic cavitation and the performance of water treatment for different types of sewage. The application of hydrodynamic cavitation reactors with different structures in water treatment are also evaluated and discussed. The design and optimization of high-performance hydrodynamic cavitation reactor are the most crucial issues for the application of hydrodynamic cavitation in water treatment. Finally, recommendations are provided for the future progress of hydrodynamic cavitation for water treatment.

Sulfadiazine degradation by combination of hydrodynamic cavitation and Fenton-persulfate: parametric optimization and deduction of chemical mechanism.

This paper reports the degradation of the sulfadiazine (SDZ) drug with a hybrid advanced oxidation process (AOP) of heterogeneous α-Fe2O3/persulfate coupled with hydrodynamic cavitation. The major objectives of the study are parametric optimization of the process and elucidation of the chemical mechanism of degradation. The optimum conditions for maximum SDZ degradation of 93.07 ± 1.67% were as follows: initial SDZ concentration = 20ppm, pH = 4, α-Fe2O3 = 181.82mg/L, Na2S2O8 = 348.49mg/L, H2O2 = 0.95mL/L, inlet pressure = 0.81MPa (8atm), orifice plate configuration: hole dia. = 2mm and number of holes = 4. Density functional theory (DFT) calculations revealed that the atoms of SDZ with a high Fukui index (f 0) were potentially active sites for the attack of •OH and [Formula: see text] radicals. Fukui index calculation revealed that atom 11N has a higher value of f 0 (0.1026) for oxidation at the α-amine group of the sulfadiazine molecule. Degradation intermediates detected through LC-MS/MS analysis corroborated the results of DFT simulations. Using these results, a chemical pathway has been proposed for SDZ degradation.

Degradation of acid red 73 wastewater by hydrodynamic cavitation combined with ozone and its mechanism

Many azo dyes are consumed in the textile and dyeing industry, which makes the wastewater recalcitrant and toxic to the aquatic environment. Dye degradation by the combination of hydrodynamic cavitation and ozone (HC + O3) has caused extensive interest. The degradation mechanism of the hybrid system needs further investigation. This study investigated the degradation of acid red 73 (AR73) by HC + O3. Meanwhile, the degradation pathways and mechanisms were present. The optimal operation parameters were: inlet pressure of 0.15 MPa, O3 dosage of 45 mg/min, initial dye concentration of 10 mg/L, and initial pH at 7.5. As a result, the decolorization rate, removal of UV254 and NH3–N were 100%, 71.28%, and 87.36% in 30 min, respectively. Humic acid and most of the co-existing anions (HCO3−, SO42−, Cl−, PO43−, NO3−) played a positive role in the degradation of AR73, while NO2− restrained. The reactive species of singlet oxygen (1O2), hydroxyl radicals (·OH) and super oxygen radicals (·O2−) showed synergism in the hybrid system, and the decolorization was attributed to the fracture of azo bonds by 1O2. Meanwhile, aromatic amines were generated and further degraded into small molecule compounds. The research certificated that the HC + O3 can be an effective technology for azo dye degradation.

Performance Evaluation of Hydrodynamic Cavitation in Combination with Aops for Degradation of Tannery Wastewater

Performance Evaluation of Hydrodynamic Cavitation in Combination with Aops for Degradation of Tannery Wastewater

Textile Industry Wastewater Treatment by Cavitation Combined with Fenton and Ceramic Nanofiltration Membrane

This work first time reports the intensification of real wastewater treatment by combination of hydrodynamic cavitation (HC), Fenton reagent, and membrane separation. In this work, a micro-porous ceramic membrane was used for the preparation of nano-porous catalytic membrane reactor. Initially, the aluminium boehmite sol has been synthesized and coated onto the tube side of the ceramic membrane by wet impregnation technique. A layer by layer technique was adopted for the wet impregnation of boehmite sol onto the ceramic membrane. After achieving a desired number of layers coating onto the ceramic membrane, a prepared catalyst sol was further used for coating. The dried boehmite powder was characterized using X-ray diffractometer and particle size distribution analysis. Mercury intrusion porosimetry (MIP) technique was used to identify the pore size distribution of modified ceramic membrane. The modified ceramic membrane was used in conjunction with HC for industrial dye wastewater treatment. The impact of process parameter such as cavitation unit (orifice) inlet pressure, intensifying chemical additive like Fenton reagent, and H2O2 dosage was investigated. HC along with intensifying chemical additives H2O2 and Fenton reagent improved the organic pollutants removal from textile industry wastewater

Synergetic degradation of atenolol by hydrodynamic cavitation coupled with sodium persulfate as zero-waste discharge process: Effect of coexisting anions

Abstract This research investigates atenolol (ATL) removal from the aqueous solution by a combination of hydrodynamic cavitation (HC) and sodium persulfate (HC-PS) as zero-waste discharge process. The effect of pH, reaction time, PS dose, initial ATL concentration, coexisting anions and natural organic matters (NOMs) has been studied. The highest ATL removal by HC and HC-PS processes was obtained at pH 3 and 6, respectively. The presence of coexisting anions viz., Cl−, NO3−, I−, SO42−, and PO43− promoted the degradation of ATL, while the efficiency of ATL degradation was inhibited by the presence HCO3− and CO32− anions and NOMs. The highest synergetic and strongest inhibition effect of ATL degradation by the HC-PS process was observed in the presence of SO42− ions (synergetic index value, 4.61) and CO32− ions (synergetic index value, 0.44). Radical trapping experiments showed that the relative contributions of hydroxyl and sulfate radical to degrade ATL were 41.7% and 58.3%, respectively. In case of HC-PS process, degradation initiated with the protonation of ATL in the presence of free active radicals was followed by the ether bond cleavage, oxidation of primary and secondary amine moieties, and finally mineralization. The HC-PS process is proved to be a potential treatment method to destroy pharmaceutical pollutants from water and wastewater sources.

Combination of hydrodynamic cavitation and SR-AOPs for simultaneous degradation of BTEX in water

• Hydrodynamic cavitation is effective in PS and PMS activation. • SO 4 •− and HO • radicals were predominant reactive species for BTEX degradation. • The inhibitory effect of inorganic anions on BTEX degradation ranked Cl − < SO 4 2− < CO 3 2– . • Surprising synergism of PMS and Cl − increased the degradation by formation of Cl-based radical species. • Degradation pathways of BTEX were proposed by intermediates identified by HPLC-DAD. Hydrodynamic cavitation (HC) is an emerging technology gaining interest in water treatment for use in elimination of a wide range of organic pollutants. The energy released during cavitation phenomenon has number of applications and, particularly, it can be utilized for activation of persulfate (PS) and peroxymonosulfate (PMS). In the present study, hybrid techniques: HC combined with persulfates – HC-PS and HC-PMS were tested for the degradation of BTEX in water. Studies on the effect of initial PS and PMS concentration showed that a molar ratio of the oxidant to BTEX equal to 5 is favorable for both cases. Thus, in 240 min HC-PS-5 process allowed to degrade 91.51%, 95.50%, 94.65%, 94.95% of benzene, toluene, ethylbenzene and o -xylene, respectively, while 90.85%, 94.50%, 94.36%, 93.07% of those compounds were degraded by HC-PMS-5. BTEX degradation pathway was proposed for HC-PS-5 and HC-PMS-5 processes relying on the identification of the main reaction intermediates using liquid chromatography coupled with UV diode array detector (HPLC-UV-DAD). Benzyl alcohol, phenol, benzoic acid, benzaldehyde and o -cresol were the main intermediates of BTEX degradation, which multistep pathway involved H-abstraction, OH addition and dealkylation in route to mineralization. At final time of treatment primary and secondary pollutants were effectively degraded. In terms of kinetics, BTEX degradation followed the pseudo-first-order reaction model and the degradation kinetics were faster in HC-PMS-5 system than in HC-PS-5. Surprisingly, the presence of chloride ions (Cl − ) in HC-PMS-5 improved the degradation efficiency of alkylated benzene derivatives indicating a synergistic effect of Cl − with SO 4 •− radicals.

Ultrafast degradation of brilliant cresyl blue under hydrodynamic cavitation based advanced oxidation processes (AOPs)

The study highlights effectiveness of hydrodynamic cavitation (HC) in the degradation of effluents polluted by Brilliant Cresyl Blue (BCB) dye. Optimal process parameters were cavitation number 0.27, inlet pressure 1.70 bar, temperature 20 °C and pH 7. The efficiency of HC was investigated in combination with other advanced oxidation processes, including the addition of external oxidants (hydrogen peroxide, ozone, and sodium persulfate) and photooxidation. A detailed investigation of reactive radical species present in the system is also presented. Hybrid processes based on HC revealed the highest synergism. Finally, ultrafast degradation of target oxazine dye (decolorization efficiency of 100%) within the short treatment time of 1 min was developed. The most effective process was a combination of hydrodynamic cavitation and ozonation with a synergistic coefficient of 1.84 and electrical energy per order EEO of 0.03 kWh m−3 order−1. The presented solution is ready to be implemented as technology for industrial practice.

Degradation of benzene present in wastewater using hydrodynamic cavitation in combination with air

The degradation of benzene present in wastewater using hydrodynamic cavitation (HC) alone as well as in combination with air has been studied using nozzles as cavitating device of HC reactor. Initially, the energy efficiency of the HC reactor operated at different inlet pressures was determined using the calorimetric studies. Maximum energy efficiency of 53.4% was obtained at an inlet pressure of 3.9 bar. The treatment processes were compared under adiabatic as well as isothermal conditions and it was observed that under the adiabatic condition, the extent of degradation is higher as compared to isothermal condition. Studies related to the understanding the effect of inlet pressure (range of 1.8–3.9 bar) revealed that the maximum degradation as 98.9% was obtained at 2.4 bar pressure using the individual operation of HC under adiabatic conditions and in 70 min of treatment. The combination of HC with air was investigated at different air flow rates with best results for maximum degradation of benzene achieved at air flow rate of 60 mL/sec. A novel approach of using cavitation for a limited fraction of total treatment time was also demonstrated to be beneficial in terms of the extent of degradation as well as energy requirements and cost of operation. Based on the cavitational intensity, the resonant radius of aggregates of cavitation bubbles was also determined for distilled water as well as for aqueous solution of benzene. Overall, significant benefits of using HC combined with air have been demonstrated for degradation of benzene along with fundamental understanding into cavitation effects.

2,4,6‐Triamino‐1,3,5‐Trinitrobenzene Explosive Wastewater Treatment by Hydrodynamic Cavitation Combined with Chlorine Dioxide

AbstractA large amount of wastewater is produced in the process of 2,4,6‐Triamino‐1,3,5‐trinitrobenzene (TATB) production, which is harmful to the environment and human health. In this work, the removal rate of chemical oxygen demand (COD) from TATB wastewater was investigated by using hydrodynamic cavitation (HC), chlorine dioxide (ClO2), and the combination of the HC and ClO2. We explored the effects of different operating parameters on extent of degradation including time (10–60 min), concentration of ClO2 (25–150 mg/L) and initial pH (6, 9.25). The result showed that the reduction of COD from explosive wastewater with initial concentration of 5407 mg COD/L was 65.9 % after a 60 min treatment with a ClO2 dosage of 150 mg/L at a pH of 6. The COD removal process by the HC/ClO2 conforms to a pseudo‐first‐order kinetic equation with a reaction rate of 20.8×10−3 min−1. We were able to determine that the HC/ClO2 method has a synergistic effect on TATB wastewater treatment with a synergetic coefficient of 3.01. By comparing the cavitational yield and cost of each process, the HC/ClO2 has a higher energy efficiency (26.78×10−3 mg/J). In conclusion, the HC/ClO2 composite process is more economical, effective, and suitable for large‐scale commercial operations.

КАВІТАЦІЯ У КОМБІНОВАНИХ ТЕХНОЛОГІЯХ ОЧИЩЕННЯ СТІЧНИХ ВОД ВІД ТОЛУЕНУ

The use of acoustic and hydrodynamic cavitation and their combinations with other methods (reagent treatment – hydrogen peroxide, Fenton reagent, ozone, etc.) for wastewater treatment from dispersed solids and organic compounds is analyzed. The feasibility of combining cavitation with rea-gent treatment to increase the degree of pollutant degradation has been demonstrated. A characteristics of the spectroscopy method in ultraviolet and visible spectral ranges is given to determine the concentration of toluene in wastewater imitation. The dependences of toluene concentration and the reaction system temperature on the duration of cavitation treatment at different values of the specific power of ultrasonic radiation, the pressure at the entrance to hydrodynamic cavitator, different reagent modes are presented. The degree of toluene degradation and the rate constant of this process for different parameters of cavitation processing are calculated. It is found that an increase in the specific power of ultrasonic radiation from 53.3 to 83.3 W/dm3 has caused a decrease in the degree of toluene degradation by 11.2 % (from 82.5 to 71.3 %), and the rate constant by 2.5 times (from 5.6·10-4 to 2.2·10-4 s-1), which is explained by two factors: the formation of Babstones and the change in the structure of the fluid according to Frenkel's kinetic theory. It is established that the use of combined technology (acoustic cavitation + hydrogen peroxide) allows to increase the rate of toluene degradation from 82.5 to 84 % and the rate constant by 26.8 % (from 5.6·10-4 to 7.1·10-4 s-1). It is determined that the combination of hydrodynamic cavitation and reagent treatment (hydrogen peroxide) allows to increase the rate of toluene degradation by 2.5 % (from 95.8 to 98.3 %). By comparing the rate constants of toluene degradation and the degradation rates for combined technologies (acoustic cavitation + H2O2; hydrodynamic cavitation + H2O2), it is found that hydrodynamic cavitation is much more efficient than acoustic one.

Decolorization of Congo red via hydrodynamic cavitation in combination with Fenton’s reagent

Congo red is a highly toxic diazoic dye used in textile industries. In this work, the decolorization of Congo red was performed using hydrodynamic cavitation (HC) individually and in combination with H2O2, FeSO4, and Fenton process. Response surface methodology (RSM) was used to design experiments and model the influence of parameters and interactions. Solution initial pH (3–10), H2O2 concentration (0−1000 mg L−1), and FeSO4 concentration (0−50 mg L -1) were selected as the parameters of the experimental investigation. A maximum decolorization of 70 % was achieved using HC in combination with Fenton’s reagent at a H2O2 concentration of 1000 mg L−1, a FeSO4 concentration of 25 mg L−1, and an initial pH of 3 within 60 min. A synergistic coefficient of 3.22 and a yield efficiency of 8.3 × 10-3 mg kJ-1 were obtained for the combined process of HC and Fenton’s reagent. The flow behavior of the HC reactor was investigated using the residence time distribution (RTD) analysis for the first time, and the results demonstrate that the tank-in-series model with two tanks almost fits the HC reactor.

A combined method of hydrodynamic cavitation and alkaline treatment for waste-activated sludge solubilization; N/P recovery from anaerobic granular sludge

Waste-activated sludge (WAS) is typically processed very slowly and only to a certain extent in anaerobic digestion (AD), typically necessitating pre-treatment. In this study, we developed a new and powerful way of pre-treating WAS, which is a combination of hydrodynamic cavitation (HC) and alkaline treatment, and examined it for its efficacy. The combined treatment yielded the highest disintegration degree (DD) of 48.4%, while HC alone produced only 11.9% of DD and alkaline alone did 16.2%. The pre-treated sludge led to much enhanced methane production compared with the untreated one; 80.7 ml/g CODadded was the largest amount of CH4 obtained with the pre-treated sludge, while 37.3 ml/g CODadded with the untreated one. The distinctive efficacy of the HC was further exploited to remove nutrients from anaerobic granular sludge (AGS) in a beneficial way: namely, the HC-mediated recovery of N/P by way of struvite precipitation. The highest phosphate removal was found at pH 10 with HC, which was more than twice the value of a simple stirring (63 mg PO43−/L by simple stirring versus 150 mg PO43−/L by HC). It appeared that HC is indeed a sure option for WAS pre- and post-treatment to improve biodegradability and nutrient recovery, respectively.

Intensification of industrial wastewater treatment using hydrodynamic cavitation combined with advanced oxidation at operating capacity of 70 L

The present work deals with treatment of industrial wastewater with hydrodynamic cavitation (HC) combined with advanced oxidation processes (AOPs) at a pilot plant operating at a capacity of 70 L. Initially approach of only HC was studied with understanding into the effect of parameters like inlet pressure (range of 2–8 bar) and dilution factor (two cases with dilution ratio as 1:1 and 1:3). Only HC was found to give minimal chemical oxygen demand (COD) removal within 180 min and the further focus of the study was aimed to test efficiency of different oxidants in combination with HC. Oxidants used in treatment were hydrogen peroxide (H2O2), Fenton’s reagent, air and oxygen. Effect of H2O2 loading was analyzed with variation of loading in the range of 5–15 g.L−1 and maximum COD removal of 30% was achieved at 15 g.L−1 loading of H2O2. Keeping 15 g.L−1 as the constant loading of H2O2, optimization of Fenton based treatment was performed with variation of Fe2+/H2O2 molar ratio in the range of 1:10–1:30. Maximum COD removal of 42% was achieved at best molar ratio of 1:20. For the very first time, air and oxygen injection were tested in combination of HC giving 15.5% and 42% COD removal respectively. Combination study of oxygen + Fenton + HC was performed at H2O2 loading of 15 g.L−1 and Fenton molar ratio as 1:20, which resulted in 63% COD removal within 180 min of treatment. Energy efficacy analysis in terms of COD reduction per unit energy and cost calculations were also performed and for process giving maximum of 63% COD removal in 180 min, cost of treatment obtained was 398 US$/m3. It was clearly established that HC in combination of Fenton and oxygen is the best approach for treatment of complex industrial wastewater.