Sewage Sludge Biomass Research Articles

Thermal hydrolysis to enhance energetic potential of sewage sludge: A review

Sewage sludge biomass is a renewable energy source commonly produced by anaerobic digestion (AD). However, the limited biodegradability of sewage sludge causes a poor energy conversion of organic material into biogas and requires further enhancement. One possible solution is sludge disintegration by a thermal hydrolysis process (THP) that has already proven to enhance biogas production and improve the quality of digested sludge. This article reviews possible THP configurations, such as THP-AD, ITHP, and PAD-THP, together with different input materials and their impact on the energy balance of the wastewater treatment plant (WWTP). Data from full-scale THP demonstrate differences between the configurations and input material. Moreover, the general advantages and disadvantages of THP integration are summarized and presented as a multicriteria analysis that simplifies the decision-making whether the THP should be integrated in the WWTP.

System integration of hydrothermal liquefaction and anaerobic digestion for wet biomass valorization: Biodegradability and microbial syntrophy

Sewage sludge treatment & disposal pose environmental challenges in populated-dense urban environments. Due to its poor digestibility and dewaterability, sewage sludge contains high water content and concentrated nutrients (carbon, nitrogen, and phosphorus) even after conditioning and mechanical thickening. Regarding this, a pretreatment step and downstream anaerobic digestion (AD) are often required. To meet our societal goal towards a circular economy, system integration of hydrothermal pretreatment and AD now present an attractive approach for recovering resources from the wet sewage sludge biomass. In this study, such system integration together with struvite precipitation was applied for valorizing sewage sludge. Firstly, hydrothermal conditions of different temperatures (160 °C–230 °C) and duration (2 h–12 h) were compared to their performance of nutrients solubilization. Subsequently, the hydrothermal condition of 220°C-3 h was selected for further investigations of struvite recovery and bioenergy production. Through AD comparisons, the integrated process improved the ultimate biomethane yield by 38%. Interestingly, a lag phase occurred in the midst of the AD, which indicated the need for microbial acclimatization after the hydrothermal process. The long-term microbial monitoring revealed the efficient biomethane re-generation was closely related to the late enrichment of Syntrophus for potential H2-syntrophy. Therefore, on one hand, this study investigated an efficient and integrated approach of sewage sludge valorization. On other hand, it uncovered the microbial bottlenecks and potential biotechnological means for further system improvement. Further research about nutrients speciation in the integrated system would be desired.

The Bioconversion of Sewage Sludge to Bio-Fuel: The Environmental and Economic Benefits.

This paper aims to analyze the economic feasibility of generating a novel, innovative biofuel—bioenergy—obtained from deposit bio-components by means of a pilot installation of sewage sludge bio-conversion. Fuel produced from sewage sludge biomass bears the potential of being considered a renewable energy source. In the present study, 23 bioconversion cycles were conducted taking into consideration the different contents, types of high carbohydrate additives, moisture content of the mixture as well as the shape of the bed elements. The biofuel was produced using post fermentation sewage sludge for industrial energy and heat generation. Based on the presented research it was concluded that the composite biofuel can be co-combusted with hard coal with the optimal percentage share within the range of 20–30% w/w. Sewage sludge stabilized by means of anaerobic digestion carried out in closed fermentation chambers is the final product. The average values of the CO2, CO, NO, NOx and SO2 concentrations in flue gas from co-combustion of a bioconversion product (20% w/w) and coal were 5.43%, 1903 ppm, 300 ppm, 303 ppm and 179 ppm, respectively. In total, within a period of 4.5 years of the plant operation, 1853 Mg of fuel was produced and successfully co-combusted with coal in a power plant. The research demonstrated that in the waste water treatment sector there exists energy potential in terms of calorific value which translates into tangible benefits both in the context of energy generation as well as environmental protection. Over 700,000 Mg of bio-sewage sludge is generated annually in Poland. According to findings of the study presented in the paper, the proposed solution could give 970,000 Mg of dry mass of biomass qualified as energy biomass replacing fossil fuels.

The synergistic effect of sewage sludge biochar and Trichoderma harzianum on soybean yield

The use of sewage sludge to produce biochar is one of the best alternatives for the final destination of this material, allowing for reuse of nutrients and reducing the dependence on mineral fertilizers. Sewage sludge biochar (SSB) stands out as an enhancer of the physical, chemical and biological properties of the soil. The use of beneficial microorganisms such as Trichoderma spp. in combination with biochar may have a synergistic effect on the development of different plants and needs to be better studied. The SSB was produced from sewage sludge biomass (SS) obtained from the sewage treatment plant (STP) of the Federal District Environmental Sanitation Company (CAESB), Brasilia, DF, Brazil. The SSB was produced in an electric tubular furnace at 500 °C and showed the following characteristics: carbon (19%), nitrogen (2.3%), hydrogen (1.7%), specific surface area (52.5 m2 g-1), pore volume (0.053 ml g-1). An experiment was carried out in a greenhouse to evaluate the synergistic effect of SSB application (0.5% w/w) in combination with T. harzianum (TH) on soybean development. The treatments adopted were: (1) control – autoclaved soil, (2) TH, (3) SSB and (4) SSB + TH. The SSB was applied 15 days before soybean planting and the TH was applied to the soil two times, once at eight days before planting and the other at the time of planting. The SSB resulted in a 200% increase in the number of pods when compared to the exclusive application of T. harzianum. Application of SSB with T. harzianum increased germination by 20%, as well as a 70% increase in fresh and dry soybean mass in relation to the control. The agronomic indices evaluated in this study demonstrated that the use of SSB in conjunction with T. harzianum presents a synergistic effect, allowing for better development of the soybean plants.

Kinetic modelling of total petroleum hydrocarbon in spent lubricating petroleum oil impacted soil under different treatments

ABSTRACTThe integration of first and second order kinetic model in parameter estimation for the degradation pattern of total petroleum hydrocarbon (TPH) in spent lubricating petroleum oil (SLPO) over a four-month period was the subject of the present investigation. Study design considered four treatment microcosms notably; sewage sludge (SB), monitored natural recovery (MNR), surfactant (SA) and control (SO). The rate of TPH degradation using sewage sludge as amendment material depicted effective TPH removal within ten weeks. A maximum allowable concentration of residual TPH (4300 mg kg−1) was obtained through an amendment with sewage sludge. Degradation constant (k) produced by both first and second order rates significantly demonstrated the performance of sewage sludge biomass over the other three treatments applied, however, experimental data adequately fitted into the first order kinetics (k = 0.27 d−1, t½ = 3.0 d). TPH removal efficiency of sewage sludge and detergent were 96.0% and 81.0% respectively. The use of sewage sludge biomass significantly (p < .05) improved soil biological characteristics and produced optimum dehydrogenase activity (DHA ≥ 8.8 TPFg−1 d), germination index (%IG ≥ 88%), and chlorophyll content (chl ≥ 100 µg cm−2), thus, recommended for field scale application in soil hydrocarbon pollution remediation.

3-13-4 下水汚泥バイオマスからの水素生成プロセスの開発(Session 3-13 糖化・発酵)

3-13-4 下水汚泥バイオマスからの水素生成プロセスの開発(Session 3-13 糖化・発酵)

Single-multicomponent biosorption of lead mercury chromium and arsenic onto activated sludge in batch and fixed-bed adsorber

A wide range of batch experiments were carried out for estimation of the key process parameters in competitive biosorption of Pb2+, Hg2+, Cr3+, and As5+ from simulated of wastewater onto dry activated sludge in batch adsorber. Eleven isotherm models were used for single component and five isotherm models for multicomponent systems. The Langmuir model gave the best fit for the data of single component, while the binary, ternary, and quaternary systems were fitted successfully with extended Langmuir model. An order of metal biosorption capacity onto dried activated sludge was found to be Pb2+ > Hg2+ > Cr3+ > As5+. FTIR analysis was carried out before and after biosorption. Pore diffusion coefficients required for fixed-bed design were determined by matching batch experimental data with the film-pore diffusion model at optimum agitation speed, 600 rpm and optimum weight of sewage sludge biomass. A general multicomponent rate model has been utilized to predict the fixed-bed breakthrough curves for multicomponent systems. Good agreement between the predicted theoretical breakthrough curves and the experimental results was observed. Results confirmed, from the feed containing Pb2+, Hg2+, Cr3+, and As5+, arsenic breakthrough from the column appeared first with higher overshoot, followed by chromium, mercury, and finally lead cations with no overshoot. COMSOL multiphysics software was used to solve the batch and fixed-bed models.

Binding sites and mechanisms of cadmium to the dried sewage sludge biomass

The Cd biosorption on the dried sewage sludge biomass were experimentally evaluated and mathematically modeled at different pH values. The potentiometric titration of the biomass was well fitted by the four-site model, which consists of three-negative and one-positive sites. The main functional groups were identified through the FTIR study. The pH edge study showed that both the carboxyl and phosphonate groups played an important role in the binding of Cd. From the dynamic biosorption experiments, the H+/Cd2+ exchange ratios at pH 4, 5 and 6 were estimated; thereby the binding mechanisms were established to be complexation with carboxyl and phosphonate groups. Finally, biosorption model was developed based upon the binding mechanism, which was successfully applied for predicting the isotherms and pH edges. Using the developed model equation, the contribution of each functional group on Cd binding could be predicted and visualized.

Alteration of sewage sludge biomass into oil-like products by hydrous pyrolysis methods

Various pyrolysis (also termed thermolysis) methods are common techniques that have been used to convert sewage sludge organic matter (OM) into useful fuels for energy. Reductive hydrous pyrolysis of OM increases the conversion yields of the sewage sludge. Our purpose is to study the effects of low temperature (<350°C) and experimental conditions in confined hydrous pyrolysis on the chemical compound compositions of the alteration products from municipal sewage sludge. These compositions have been determined by gas chromatography-mass spectrometry. Two sets of experiments were conducted at temperatures ranging from 200 to 350°C with contact periods of 48h. The reaction mixtures of the first set included only sewage sludge and water, whereas the second set also contained oxalic acid to provide excess hydrogen to enhance reduction of the organic matter of sewage sludge. The yields and the number of observed alteration products increased with higher temperature and presence of aqueous oxalic acid in the reaction mixtures. At lower temperatures n-alkanoic acids, n-alkanols and sterols were the major compounds. Hydrocarbon concentrations increased at higher temperatures in both experiment sets, except for UCM (unresolved complex mixture), which decreased >300°C. The n-alkanes increased dramatically with temperature increase both in the presence and absence of oxalic acid, where their yields were high in the former medium. Sterane concentrations also increased at elevated temperatures, being highest in the presence of oxalic acid. The products confirm that alteration of sewage sludge biomass in aqueous medium occurs rapidly and efficiently under reductive pyrolysis conditions, and in the temperature window of 250–350°C. These results show that the product yields are higher by a factor of 1.4 under reductive hydrous pyrolysis versus hydrous pyrolysis conditions.

Cadmium ion removal by electroflotation onto sewage sludge biomass

Non-living, anaerobically digested, Activated-Sludge (AS) was examined (laboratory-scale experiments) as possible biosorbent for the removal of cadmium from dilute aqueous solutions. The application of electroflotation to the suspended biomass, was investigated in this paper as an effective solid/liquid separation technique for the metal-loaded biosorbent particles. The main parameters influencing this combined bioremediation process were examined, including the electric current density, flotation time, pH value, biomass addition and cadmium ion concentration, as well as the solution ionic strength. Promising results were obtained, as removals over 90% were achieved for both metal and biomass during one-stage.

Mechanistic evaluation of the sorption properties of endocrine disrupting chemicals in sewage sludge biomass

This study investigated the sorption behaviour of two endocrine disrupting chemicals; 17β-estradiol (E2) and 17β-ethinylestradiol and their thermodynamic properties in an activated sludge biomass. The partition coefficient values measured for E2 and EE2 at varying temperatures range from 245–604 L/kg ( log Kd 2.39–2.78) and 267–631 L/kg (Log Kd 2.43–2.80), respectively. The Kd values were inversely related to temperature. The average percentages of E2 and EE2 adsorbed to the solid phase at 4.3 % dry solid were 87.2 % and 92.5 %, respectively. Sorption of E2 and EE2 to the activated sludge biomass was found to be spontaneous and entropy retarded with ΔG values in the range of −13 to −16 KJ/mol and ΔS value of−105.2J/mol/K and 96.7 J/mol/k for E2 and EE2, respectively. The enthalpy changes for E2 and EE2 were −45.7KJ/mol and −43.4KJ/mol respectively, demonstrating that the sorption process is exothermic. The values of the enthalpy changes also show that the mechanism of sorption is physisorption with some element of chemisorption.