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In this study, an attempt has been made to reduce the sludge using novel homogenizer coupled solar photo Fenton (HPF) process. At an optimum pH of 3 and Fe2+ to H2O2 dosage of 1:6, PF process yielded 63.7% solids reduction at a time interval of 45 min. Coupling of homogenizers with photo Fenton (PF) process effectively enhanced treatment efficiency. When homogenizer (specific energy - 1150.694 kJ/kg TS) was coupled with PF, a sharp increase in solid reduction 73.5% and decrease in reaction time (20 min) were observed. Cost benefit analysis revealed the efficiency of HPF process and achieved a net cost of 15.59 USD whereas PF achieved a negative net cost of −82.69 USD. Based on the above study it can be concluded that coupling of homogenizers with PF not only increased its efficiency but also make it field applicable.

Waste activated sludge (biosolids) treatment is intensely a major problem around the globe. Anaerobic treatment is indeed a fundamental and most popular approach to convert organic wastes into bioenergy, which could be used as a carbon-neutral renewable and clean energy thus eradicating pathogens and eliminating odor. Due to the sheer intricate biosolid matrix (such as exopolymeric substances) and rigid cell structure, hydrolysis becomes a rate-limiting phase. Numerous different pretreatment strategies were proposed to hasten this rate-limiting hydrolysis and enhance the productivity of anaerobic digestion. This study discusses an overview of previous scientific advances in pretreatment options for enhancing biogas production. In addition, the limitations addressed along with the effects of inhibitors in biosolids towards biogas production and strategies to overcome discussed. This review elaborated the cost analysis of various pretreatment methods towards the scale-up process. This review abridges the existing research on augmenting AD efficacy by recognizing the associated knowledge gaps and suggesting future research.

This paper proposed to interpret the novel method of extracellular polymeric substance (EPS) removal in advance to sludge disintegration to enrich bioenergy generation. The sludge has been subjected to deflocculation using Zinc oxide/Chitosan nanocomposite film (ZCNF) and achieved 98.97% of solubilization which enhance the solubilization of organics. The obtained result revealed that higher solubilization efficiency of 23.3% was attained at an optimal specific energy of 2186 kJ/kg TS and disintegration duration of 30 min. The deflocculated sludge showed 8.2% higher solubilization than the flocculated sludge emancipates organics in the form of 1.64 g/L of SCOD thereby enhancing the methane generation. The deflocculated sludge produces methane of 230 mL/g COD attained overall solid reduction of 55.5% however, flocculated and control sludge produces only 182.25 mL/g COD and 142.8 mL/g COD of methane. Based on the energy, mass and cost analysis, the deflocculated sludge saved 94.1% of energy than the control and obtained the net cost of 5.59 $/t which is comparatively higher than the flocculated and control sludge.

The proposed work intended to improve sludge reduction efficiency of dark Fenton (DF) treatment. Dark Fenton reduces 61% of sludge in 90 min under the optimized Fe (II) and H2O2 dosage of 0.008 g/g suspended solids (SS) and 0.032 g/g SS respectively at pH 3. Combination of dark Fenton with disperser (DFD) reduces time required for the treatment from 90 to 30 min with the disperser specific energy input of 835.536 kJ/kg total solids (TS). At 30 min reaction time, mixed liquor suspended solids and total chemical oxygen demand reduction were found to be 65% and 60%, respectively for DFD. The efficiency of DFD treatment revealed best fit with R2 value of 0.989 during pseudo first order kinetic analysis. The synergistic effect of DFD resulted in 29% higher MLSS reduction and 31% higher TCOD reduction than dark Fenton (DF) in 30 min treatment as the obtained MLSS and TCOD reduction at 30 min treatment time was observed to be 65% and 60% in DFD and 36% and 29% in DF, respectively. Although, DFD demands higher energy input (233.69 kWh), it had potency to reduce higher solids concentration in a short duration and this results in a net profit of 12.852 USD/ton of sludge.

This research work aimed about the enhanced bio-hydrogen production from marine macro algal biomass (Ulva reticulate) through surfactant induced microwave disintegration (SIMD). Microwave disintegration (MD) was performed by varying the power from 90 to 630 W and time from 0 to 40 min. The maximum chemical oxygen demand (COD) solubilisation of 27.9% was achieved for MD at the optimal power (40%). A surfactant, ammonium dodecyl sulphate (ADS) is introduced in optimal power of MD which enhanced the solubilisation to 34.2% at 0.0035 g ADS/g TS dosage. The combined SIMD pretreatment significantly reduce the treatment time and increases the COD solubilisation when compared to MD. Maximum hydrogen yield of 54.9 mL H2 /g COD was observed for SIMD than other samples. In energy analysis, it was identified that SIMD was energy efficient process compared to others since SIMD achieved energy ratio of 1.04 which is higher than MD (0.38).

In this study, recalcitrant rich retting-pond wastewater was treated primarily by anaerobic treatment and subsequently treated with a solar photofenton process to remove phenol and organics. The anaerobic treatment was carried out in a granulated laboratory scale hybrid upflow anaerobic sludge blanket reactor (HUASBR) with a working volume of 5.9 L. It was operated at different hydraulic retention times (HRT) from 40 to 20 h over a period of 140 days. The optimum HRT of the anaerobic reactor was found to be 30 h, with corresponding chemical oxygen demand (COD) and phenol removal of 60% and 47%, respectively. Primary anaerobically treated wastewater was subjected to secondary solar photofenton treatment which was carried out at pH 3.5. Response surface methodology (RSM) was used to design and optimize the performance of the solar photofenton process. Regression quadratic model describing COD removal efficiency of the solar photofenton process was developed and confirmed by analysis of variance (ANOVA). Optimum parameters of the solar photofenton process were found to be: 4 g/L of fenton as catalysts, 25 mL of hydrogen peroxide, and 30 min of reaction time. After the primary anaerobic treatment, solar photofenton oxidation process removed 94% and 96.58% of COD and phenol, respectively. Integration of anaerobic and solar photofenton treatment resulted in 97.5% and 98.4% removal of COD and phenol, respectively, from retting-pond wastewater.