Optimization of protein recovery from sewage sludge via controlled and energy-saving ultrasonic-alkali hydrolysis

Lentil protein isolate (Lens culinaris) subjected to ultrasound treatment combined or not with heat-treatment: structural characterization and ability to stabilize high internal phase emulsions

This study evaluated the effect of ultrasound treatment combined or not with heat treatment applied to lentil protein isolate (LPI) aiming to enhance its ability to stabilize high internal phase emulsions (HIPE). LPI dispersion (2%, w/w) was ultrasound-treated at 60% (UA) and 70% (UB) amplitude for 7 min; these samples were subjected to and then heat treatments at 70 °C (UAT70 and UBT70, respectively) or 80 °C (UAT80 and UBT80, respectively) for 20 min. HIPEs were produced with 25% untreated and treated LPI dispersions and 75% soybean oil using a rotor-stator (15,500 rpm/1 min). The LPI dispersions were evaluated for particle size, solubility, differential scanning calorimetry, electrophoresis, secondary structure estimation (circular dichroism and FT-IR), intrinsic fluorescence, surface hydrophobicity, and free sulfhydryl groups content. The HIPEs were evaluated for droplet size, morphology, rheology, centrifugal stability, and the Turbiscan test. Ultrasound treatment decreased LPI dispersions' particle size (∼80%) and increased solubility (∼90%). Intrinsic fluorescence and surface hydrophobicity confirmed LPI modification due to the exposure to hydrophobic patches. The combination of ultrasound and heat treatments resulted in a reduction in the free sulfhydryl group content of LPI. HIPEs produced with ultrasound-heat-treated LPI had a lower droplet size distribution mode, greater oil retention values in the HIPE structure (> 98%), lower Turbiscan stability index (< 2), and a firmer and more homogeneous appearance compared to HIPE produced with untreated LPI, indicating higher stability for the HIPEs stabilized by treated LPI. Therefore, combining ultrasound and heat treatments could be an effective method for the functional modification of lentil proteins, allowing their application as HIPE emulsifiers.

The feasibility and applicability of sequential extraction of high value-added biogenic materials from sewage sludge

The sequential extraction routes of biogenic materials from sewage sludge (SS) were investigated. Physical methods (ultrasound, heating) and chemical methods (sodium hydroxide, sodium carbonate) were used to extract extracellular polymeric substances (EPS) and alginate-like extracellular polymers (ALEs) from SS. The residues after extraction were further subjected to physical methods (heating) and chemical methods (sulfuric acid, sodium hydroxide) for protein extraction. A comparison was made between sequential extraction routes and direct extraction of biomaterials from sludge in terms of extraction quantity, material properties, and applicability. The results showed that sequential extraction of biomaterials is feasible. The highest extraction quantities were obtained when using sodium carbonate for EPS and ALE extraction and sodium hydroxide for protein, reaching 449.80 mg/gVSS, 109.78 mg/gVSS, and 5447.08 mg/L, respectively. Sequential extraction procedures facilitate the extraction of biomaterials. Finally, suitable extraction methods for different application scenarios were analyzed.

Optimizing sludge dewatering efficiency with ultrasonic Treatment: Insights into Parameters, Effects, and microstructural changes

Sludge dewatering plays a critical role in the efficient and cost-effective management of wastewater treatment plants. Ultrasonic treatment has emerged as a promising technique for improving dewatering processes. This study aims to evaluate the impact of ultrasonic treatment on sludge dewatering characteristics. A series of experiments were conducted to evaluate the dewatering characteristics of sludge under ultrasonic treatment. Experimental data was collected, and the effects of ultrasonic parameters on dewatering efficiency were analyzed. Ultrasound has the capacity to disintegrate sludge flocs, liberate tightly bound water, and enhance sludge dewatering capabilities. The application of ultrasound leads to the breakdown of sludge flocs, which facilitates a substantial amount of organic acids or carbonates. This, in turn, modifies the pH value of the sludge. Additionally, ultrasound induces instantaneous high temperature and pressure within the liquid phase, consequently elevating the temperature of the sludge slurry. Optimum ultrasound energy density and duration of ultrasound treatment exist. For the sludge samples analyzed in this investigation, it was determined that the optimal ultrasonic energy density is 9.8 W, while the optimal duration of ultrasound treatment is 30 s. Excessively escalating the sound energy density or prolonging the duration of ultrasound may yield unfavorable outcomes in terms of sludge dewatering effectiveness. To enhance sludge dewatering, it is crucial to select appropriate ultrasonic energy density and duration of ultrasonic treatment. This study demonstrates the positive impact of ultrasonic treatment on the dewatering characteristics of sludge. The findings provide valuable insights into the potential of ultrasonic technology for enhancing sludge dewatering.