Reactors R1 Research Articles

Hardness Reduction using Waste Plastic

This study focused on the utilisation of waste plastic as an ion exchanger to reduce water hardness. The three identical glass columns R1, R2, and R3 were used, each containing different types of waste plastic resin, such as styrofoam resin (SR), air bubble plastic resin (AR), or a mixture of both resins (MR), respectively. The plastics underwent a sulfonation process after crushing and sieving; their sulfonation was confirmed using FTIR analysis. For lab-scale experiments, each glass column was filled with sand, gravel, and coconut fiber as supporting media and equipped with a pump and flow-control valves. Groundwater collected from an urban area was passed through the columns at different flow rates and contact times. The process takes place by exchanging the Na+ ions of resins with polluting ions present in hard water. The treatment parameters involved are total hardness, calcium hardness, magnesium hardness, chloride, TDS, and pH. During the treatment process, pH was maintained between 7 and 8.5. All the parameters were tested twice, and the average of the observations was noted. The results showed that the maximum total hardness reduction achieved in reactors R1, R2, and R3 was 63%, 52%, and 58.6%, respectively, at a contact time of 24 h.

Effect of microalgae and bacteria inoculation on the startup of bioreactors for paper pulp wastewater and biofuel production

The use of microalgae and bacteria as a strategy for the startup of bioreactors for the treatment of industrial wastewater can be a sustainable and economically viable alternative. This technology model provides satisfactory results in the nitrification and denitrification process for nitrogen removal, organic matter removal, biomass growth, sedimentation, and byproducts recovery for added-value product production. The objective of this work was to evaluate the performance of microalgae and bacteria in their symbiotic process when used in the treatment of paper pulp industry wastewater. The experiment, lasting fourteen days, utilized four bioreactors with varying concentrations in mgVSS/L of microalgae to bacteria ratio (R1-100:100, R2-100:300, R3-100:500, R4-300:100) in the startup process. Regarding the sludge volumetric index (SVI), the results show that the R1 and R2 reactors developed SVI30/SVI10 biomass in the range of 85.57 ± 7.33% and 84.72 ± 8.19%, respectively. The lipid content in the biomass of reactors R1, R2, R3 e R4 was 13%, 7%, 19%, and 22%, respectively. This high oil content at the end of the batch, may be related to the nutritional stress that the species underwent during this feeding regime. In terms of chlorophyll, the bioreactor with an initial inoculation of 100:100 showed better symbiotic growth of microalgae and bacteria, allowing exponential growth of microalgae. The total chlorophyll value for this bioreactor was 801.46 ± 196.96 μg/L. Biological removal of nitrogen from wastewater from the paper pulp industry is a challenge due to the characteristics of the effluent, but the four reactors operated in a single batch obtained good nitrogen removal. Ammonia nitrogen removal performances were 91.55 ± 9.99%, 72.13 ± 19.18%, 64.04 ± 21.34%, and 86.15 ± 30.10% in R1, R2, R3, and R4, respectively.

Performance of rice husk biocarrier on ammonia nitrogen removal in the MBBR treating aquaculture wastewater using biological attached growth process: Performance and kinetic study

This study investigates the feasibility of using rice husk (RH) as a cost-effective and environmentally friendly bio-carrier for immobilizing isolated microorganisms to treat synthetic recirculating aquaculture system (RAS) ‎wastewater. Two moving bed biofilm reactors (MBBR) inoculated with indigenous microorganisms were operated simultaneously for 391 days under various ‎cycle times and compared. The RH and Kaldnes-3 (K3) bio-carriers were placed in reactors R1 and R2, respectively.‎ The results indicated that at constant influent TAN, with increases in cycle ‎time from 6 to 24 h, TAN and COD ‎removal ‎efficiencies ‎increased in both bioreactors; but at an optimum cycle time of 6 h, the TAN and COD removal efficiencies were‎ ‎82 ± 1.5% ‎ ‎and‎ 77.9 ± 1.7%‎‎ for the R1 and, 89.9 ± 3.3%‎ ‎and ‎84 ± 1.2% ‎for the R2, respectively. Also, at a constant cycle time, ‎the performance of R2 was better ‎compared to R1 filled with RH. Microbial identification confirmed the presence of four dominant genera, including Arthrobacter, Bacillus, ‎Rhodococcus, and ‎Staphylococcus, which were heterotrophic nitrification bacteria (HNB). The TAN removal kinetics were investigated using a Modified Stover-Kincannon (MSK) model. In reactors R1 and R2, the biokinetic constants were determined to be Umax: 0.116 and 0.149 g/Lday, and KB: 0.158 and 0.182 g/Lday, respectively. The correlation coefficients (R2) of the MBBRs were higher than 0.97, indicating that the model adequately described the experimental data.

Thermo‐economic assessment of a bench‐scale pyrolysis unit through a process simulator

AbstractThis article focuses on the holistic appraisal of a pilot‐scale updraft reactor (E1) powered by the processed residue of forest waste (W1) and hog fuel (W2). The detailed analysis of the up‐draft unit includes the availability of energy, economic evaluation, and the determination of the lignocellulose content of the pine waste. The reformed structure of the pine pellet was used for gas, bio‐oil, and char generation. The Aspen HYSYS process simulator was used for simulation purposes and the results were validated with the solution obtained experimentally. For the measurement of the constituent contents of the pine needles, the National Renewable Energy Laboratory (NREL) procedure was adopted. To investigate the similitude of the packed bed reactor, the Soave–Redlich–Kwong model was considered. For comparison of the given prototype, five different reactor types – conversion (R1), equilibrium (R2), Gibbs (R3), continuous stir tank (CST) (R4) and plug flow (R5) – were juxtaposed and their thermodynamic behavior was evaluated. From structural composition, it was noticed that the cellulose and hemicellulose(s) content dropped by 24.95% and 37.37%, respectively, whereas a rise of 23.33% was seen in the acid‐insoluble lignin (AIL) fraction of forest waste after the torrefaction process. Irrespective of the fuel type, the unconsumed fuel percentage was the same for both wood and processed residue pellets for R5. The relative percentage of methane increased by 1% for processed forest residue. The CO2 emission was estimated to be maximum for reactors R3 and R4. The O2 gain was absent in the R2 reactor. Concomitantly, it gained momentum in R1, R3, and R4. The simulated polytropic equations of state for W1 and W2 were PV1.083 = C and PV1.092 = C, respectively. The levelized cost of energy dropped by 12.50% while scaling up a pyrolysis unit.

Anaerobic co-digestion of food waste, bio-flocculated sewage sludge, and cow dung in CSTR using E(C2)Tx synthetic consortia

In the current study, a E(C2)Tx synthetic consortia was tested for anaerobic co-digestion of food waste (FW), bio-flocculated sewage sludge (BFS)/ raw wastewater (RW) and cow dung (CD) at varying proportions in 0.25 L and 6.5 L mesophilic continuously stirred tank reactors. Anaerobic co-digestion of FW with CD and RW at the ratio of 1:1:8 in 0.25 L batch-reactor with E(C2)Tx inoculum resulted in the highest H2 production with least CO2 release. The microbial dynamics of FW:CD:RW samples were studied using 16S metagenomic sequencing which indicated a predominance of hydrolysing microbes at the end point of the digestion cycle. Subsequently, the experiments were scaled up in two continuous digesters, namely, R1 (fed with 50% FW and 50% BFS) and R2 (fed with 2% FW and 98% BFS) with 6.5 L working volume at 2.5 g VS L−1D−1 organic loading rate (OLR) for 120 days. The highest VFA production of 19,183 mg L−1 and 3,265 mg L−1 with maximum bio-methane yield of 142.21- and 225.03-mL CH4g−1 VSadded were recorded in reactors R1 and R2, respectively. In addition, a numerical analysis was conducted to visualize the mixing and temperature distribution within the digesters, and the velocity and temperature profiles were obtained using Ansys Fluent.

Stability of aerobic granular sludge for simultaneous nitrogen and Pb(II) removal from inorganic wastewater

ABSTRACT In this paper, we proposed a strategy for the establishment of an aerobic granular sludge (AGS) system for simultaneous nitrogen and Pb(II) removal from inorganic wastewater. AGS was stored in lead nitrate solution to select functional bacteria resistant to lead poison, and then an AGS system for ammonia nitrogen (180-270 mg/L) and Pb(II) (15-30 mg/L) removal was established based on carbon dosing and a two-stage oxic/anoxic operational mode. After storage for 40 days, the stability of AGS decreased because specific oxygen uptake rate, nitrification rate and abundance of Nitrosomonas decreased to different degrees compared with those before storage. During the first 70 days of the recovery process, AGS in R1 (the blank reactor) and R2 (the control reactor) both experienced a first breakage and then regranulation process. The main properties of AGS in reactors R1 and R2 tended to be stable after days 106 and 117, respectively, but the structure of steady-state AGS in R2 was more compact. The total inorganic nitrogen (TIN) in effluent from R1 and R2 basically remained below 25 mg/L after days 98 and 90, respectively. The Pb(II) concentration in effluent from R2 was always below 0.3 mg/L. On day 140, the relative abundance of Nitrosomonas in R2 (6.17%) was significantly lower than that in R1 (12.15%), whereas the relative abundance of denitrifying bacteria was significantly higher than that in R1 (62.44% and 46.79%). The system removed 1 kg of influent TIN only consuming approximately 1.85 kg of carbon source, demonstrating clear advantages in energy savings.

Anaerobic treatment of ultrasound pretreated palm oil mill effluent (POME): microbial diversity and enhancement of biogas production.

In this study, palm oil mill effluent (POME) treated by ultrasonication at optimum conditions (sonication power: 0.88W/mL, sonication duration: 16.2min and total solids: 6% w/v) obtained from a previous study was anaerobically digested at different hydraulic retention times (HRTs). The reactor biomass was subjected to metagenomic study to investigate the impact on the anaerobic community dynamics. Experiments were conducted in two 5 L continuously stirred fill-and-draw reactors R1 and R2 operated at 30 ± 2°C. Reactor R1 serving as control reactor was fed with unsonicated POME with HRT of 15 and 20days (R1-15 and R1-20), whereas reactor R2 was fed with sonicated POME with the same HRTs (R2-15 and R2-20). The most distinct archaea community shift was observed among Methanosaeta (R1-15: 26.6%, R2-15: 34.4%) and Methanobacterium (R1-15: 7.4%, R2-15: 3.2%). The genus Methanosaeta was identified from all reactors with the highest abundance from the reactors R2. Mean daily biogas production was 6.79 L from R2-15 and 4.5 L from R1-15, with relative methane gas abundance of 85% and 73%, respectively. Knowledge of anaerobic community dynamics allows process optimization for maximum biogas production.

Simultaneous ammonium and sulfate biotransformation driven by aeration: Nitrogen/sulfur metabolism and metagenome-based microbial ecology

The present study aimed to clarify the effect of oxygen respiration on biotransformation of alternative electron acceptors (e.g., nitrate and sulfate) underlying the simultaneous removal of ammonium and sulfate in a single aerated sequencing batch reactor. Complete nitrification was achieved in feast condition, while denitrification was carried out in both feast and famine conditions when aeration intensity (AI) was higher than 0.22 L/(L·min). Reactors R1 [0.56 L/(L·min)], R2 [0.22 L/(L·min)], and R3 [0.08 L/(L·min)] achieved 72.39% sulfate removal efficiency in feast condition, but H2S release occurred in R3. Following exogenous substrate depletion, sulfate concentration increased again and exceeded the influent value in R1, indicating that sulfate transformation was affected by oxygen intrusion. Metagenomic analysis showed that a higher AI promoted sulfate reduction by switching from dissimilatory to assimilatory pathway. Lower AI-acclimated microorganisms (R3) produced H2S and ammonium, while higher AI-acclimated microorganisms (R1) accumulated nitrite, which confirmed that biotransformation of N and S was strongly regulated by redox imbalance driven by aeration. This implied that respiration control, a microbial self-regulation mechanism, was linked to the dynamic imbalance between electron donors and electron acceptors. Aerobic nitrate (sulfate) reduction, as one of the effects of respiration control, could be used as an alternative strategy to compensate for dynamic imbalance, when supported by efficient endogenous metabolism. Moderate aeration induced microorganisms to change their energy conservation and survival strategy through respiration control and inter-genus protection of respiratory activity among keystone taxa (including Azoarcus in R1, Thauera in R2, and Thiobacillus, Ottowia, and Geoalkalibacter in R3) to form an optimal niche in response to oxygen intrusion and achieve benign biotransformation of C, N, and S without toxic intermediate accumulation. This study clarified the biotransformation mechanism of ammonium and sulfate driven by aeration and provided theoretical guidance for optimizing existing aeration-based techniques.

Waste to Energy: Calorific Improvement of Municipal Solid Waste through Biodrying

Abstract Municipal solid waste (MSW) is an energy resource with sufficient energy/calorific value, making it a suitable substitute for fuel. This study investigated the effect of air flow rate on the MSW calorific value, the hemicellulose content, and the MSW degradation rate in a biodrying process. Four biodrying reactors equipped with flowrate and temperature recorders were used in the study. The air flow rate was varied as follows: 0 L/min/kg, 2 L/min/kg, 4 L/min/kg, and 6 L/min/kg, corresponding to reactors R1, R2, R3, and R4, respectively. The calorific value, water content, hemicellulose content, organic C content, and total N were measured on day 1, day 15, and day 30. The results showed that the biodrying process could increase the calorific value by 55.3 %, whereas the control reactor could increase the calorific value by only 4.7 %. The highest calorific value was 17.63 MJ/kg, at an air flow rate of 4 L/min/kg. The air flow rate had a significant effect on increasing the calorific value (sig.<0.05). The highest temperature in the biodrying process was 41 °C. The final MSW moisture content was 27.28 %, resulting from R4. According to the statistical test results, the air flow rate had a significant influence on the water content parameters. Hemicellulose degradation due to air flow rate reached 80–85 %. The air flow rate did not significantly influence the hemicellulose degradation (sig.>0.05). The biodrying process is the suitable method to increase the calorific value of MSW while reducing its water content; thus, the process promotes the realization of waste to energy as refuse-derived fuel.

Performance Comparison of Single and Two-Phase Biogas Digesters Treating Dairy Cattle Manure at Tropical Ambient Temperature

The biodegradation process of organic waste in anaerobic digestion can be in a single or two-phase bio-reactor. This study examined the effect of different biogas digester configurations (single and two-phase) on methane production of dairy cattle manure (DCM) at tropical ambient temperature. Three identical reactors were used in this study (R1, R2, and R3). The two-phase digesters consisted of reactors R1 and R2. R1 had a 2.1 L working volume and 3 d hydraulic retention time (HRT), while R2 had 5.25 L working volume and 22 d HRT (R1 and R2 had a 25 d HRT). The digested slurry of R1 was used to feed R2. R3 served as the single-phase digester and had 5.25 L working volume and 25 d HRT. Methane production were 14.31, 132.82, and 146 L/kg VS for R1, R2, and R3, respectively. The results showed that there was no positive effect of the application of a two-phase digester configuration on the specific methane yield of DCM per kg volatile solids added than that in the single-reactor. Methane production was detected in the first reactor of the two-phase digester configuration and the total methane production of the two-phase digester was found to be 29.98% higher (p<0.05) than that of the single reactor in terms of digester volume (0.41 VS 0.31 L/L/d). Both digester configurations performed well, indicated by a stable methane production and low volatile fatty acids and total ammonia concentrations. The two-phase bio-digester configuration can significantly increase methane production in terms of digester volume.

Performance of novel sponge biocarrier in MBBR treating recirculating aquaculture systems wastewater: Microbial community and kinetic study

In this study, a novel sponge biocarriers (SB) in moving bed bioreactor (MBBR) treating recirculating aquaculture systems wastewater was evaluated for the first time. Two lab-scale MBBRs were operated simultaneously for 116 days under various hydraulic retention times (HRTs). The reactors R1 and R2 were filled with K5 plastic carriers and SB, respectively. From the results, at an optimum HRT of 6 h, ammonia removal efficiency and nitrification rate were 86.67 ± 2.4% and 1.43 mg/L.h for the R1 and, 91.65 ± 1.3% and 1.52 mg/L.h for the R2, respectively. The microbial community analysis showed that the predominant genera in the nitrifying community were Nitrosomonas (AOB) and Nitrospira (NOB) in co-existence with heterotrophic genera Hyphomicrobium, Mesorhizobium, Zhizhongheella, and Klebsiella spp. Modified Stover-Kincannon model examined the ammonia removal kinetics, and the values of kinetic parameters obtained were Umax: 0.909 and 1.111 g/L.d and KB: 0.929 and, 1.108 g/L.d for the R1 and R2, respectively. The correlation coefficients (R2) of the MBBRs were higher than 0.98, indicating that the model adequately described the experimental data. Overall, MBBR, filled with the proposed novel SB operated at 6 h HRT, can achieve the highest nitrification performance and increase the diversity of the functional microbial communities.

Nitrogen and Phosphorus Removal from Domestic Sewage Aerobic Granular Sludge Under Intermittent Gradient Aeration

In this study, three SBR reactors R1, R2, and R3 were set up and operated using (A/O)3-SBR gradient aeration, (A/O)3-SBR constant aeration, and the conventional (A/O)-SBR mode, respectively. The nutrient removal performance and aerobic granular sludge characteristics under these aeration modes were explored using real municipal wastewater as the influent matrix. The experimental results revealed that for the R1, R2, and R3 particles during the stable period, the average removal rate of COD was 88.68%, 89.05%, and 88.96%, respectively, the average removal rate of TN was 76.97%, 71.99%, and 64.92%, respectively, the average removal rate of TP was 96.28%, 85.05%, and 78.97%, respectively, and the proportion of denitrifying phosphorus accumulating bacteria to phosphorus accumulating bacteria was 25.52%, 19.60%, and 12.77%, respectively. The results showed that the operation mode of anaerobic, aerobic, and anoxic was more conducive to the enrichment of denitrifying phosphorus accumulating bacteria (DPAOs), and that the gradient aeration was more enriched than the constant aeration mode, which is of great significance to low-intensity municipal domestic sewage treatment with an insufficient carbon source. At the same time, the dissolved oxygen in the aeration section of R1 was reduced step-by-step, which improved the simultaneous nitrification and denitrification rates of particles and the utilization rate of the internal carbon source, which was beneficial for the efficient removal of TN. The particle size of the three groups of reactors was 727.368, 815.072, and 895.041 μm respectively. As the transfer rate of the matrix decreased with particle size, the microorganisms in R2 and R3 may have caused anaerobic respiration to release harmful gas, thus damaging the particle structure, such that the particles in R2 and R3 were less dense than those in R1. In addition, the PN/PS values of R1, R2, and R3 were 6.31, 5.63, and 4.83, respectively, and the EPS content (in terms of VSS) was 103.97, 92.22, and 76.98 mg·g-1, respectively, at the time of particle stabilization, which revealed that the mode of intermittent gradient aeration was beneficial to stimulate the secretion of EPS. This was especially the case for the secretion of PN, which increased the PN/PS value, enhanced the cell hydrophobicity, and made the particles dense and stable.

Calcium ions affect sludge digestion performance via changing extracellular polymeric substances in anaerobic bioreactor

In this study, batch tests were conducted with and without the addition of calcium ions to clarify the interaction between calcium ions and extracellular polymeric substances (EPS). The maximum degradation rates of EPS and chemical oxygen demand (COD) in the reactor with the addition of Ca2+ reached 58.26, 67.19, 69.35 mg∙g−1 mixed liquor suspended solids (MLSS) and 89.70%, 94.04%, 91.70%, respectively, and were higher than those in the control reactor. The results showed that Ca2+ (1000–2000 mg∙L−1) significantly promoted the secretion of EPS and improved sludge digestion performance during the process of anaerobic digestion. In addition, Ca2+ changed the functional groups of EPS and the microstructure of granular sludge compared with the control reactor. The concentrations of EPS in the reactor with added Ca2+ were positively correlated with the COD degradation rate, with coefficients of determination of 0.88, 0.91, and 0.98 in reactors R1, R2, and R3, respectively, which suggests that EPS can affect the bioactivity of anaerobic granular sludge (AnGS), and particularly the degradation of organics. The results were reaffirmed by analyzing volatile fatty acids (VFAs) and cytochrome c (c-Cyts). There was no obvious relationship between the EPS content and COD degradation rate in the control reactor (R2 = 0.63), which indicates that Ca2+ may be an important factor in attaining the above results. Therefore, we speculate that Ca2+ caused changes in EPS, as the concentration of EPS increased and the COD degradation rate increased (and vice versa), which affected the digestion performance of AnGS.

Thermodynamic potential of a novel plasma-assisted sustainable process for co-production of ammonia and hydrogen with liquid metals

In the present article, the thermodynamic potential of a sustainable plasma-assisted nitrogen fixation process for co-production of ammonia and hydrogen is investigated. The developed process takes advantage of chemical looping system by using a liquid metal such as gallium to drive nitrogen fixation reaction using three reactors including reactor R1 to produce gallium nitride from gallium and nitrogen, reactor R2 to produce ammonia and hydrogen from gallium nitride, and plasma reactor R3 to convert gallium oxide to pure gallium. The results of the thermodynamic assessments showed that the proposed reactions are spontaneous and feasible to occur in the reactors. Likewise, the first two reactions are exothermic with ΔH=-230kJmol and ΔH=-239kJmol in the reactors R1 and R2, respectively with an equilibrium chemical conversion of 100%. The plasma reactor requires thermal energy to drive an endothermic reaction of gallium oxide dissociation withΔH=+870kJmol. Thermochemical equilibrium analysis showed that the molar ratio of steam to GaN, as well as the operating pressure and temperature of reactor R2 are the main operating parameters identifying the product composition in the reactor such that by increasing the temperature, the molar ratio of hydrogen to ammonia increases. However, by increasing the molar ratio of steam/GaN (φ value) from 0.1 to 1, the hydrogen content of the reactor increases from 45% to 70% at 400 °C. For φ > 1.0, the hydrogen content decreases while more hydrogen participate in the formation of NH3 thereby increasing the mole fraction of ammonia in the reactor. The equilibrium chemical conversion of all three reactors is expected to reach the completion point (χ = 100%) due to the highly negative Gibbs free energy of the liquid metal-based reactions together with a large thermal driving force supported by thermal plasma reactor. Finally, a scalability study points at a possible use of the new disruptive process design at small scale, and possible industrial transformation scenarios for a distributed production at a local site of consumption are depicted.

Aerobic Granular Sludge System with Multiple Influent-Aeration Operation Strategy

SBR reactors R1 and R2 were used to inoculate activated sludge from a sewage treatment plant, and domestic sewage was used as the influent. The operation was carried out using a single and multiple influent-aeration operation strategy, respectively, and the particle size change and removal effect during the operation was studied. The results show that R1 and R2 successfully achieved sludge granulation after 56 days and 39 days of operation, respectively. The concentrations (mg·L-1) of chemical oxygen demand, total nitrogen, and total phosphorus (TP) in the effluent of R1 and R2 after stable operation were 29.7, 13.7, 0.31, 19.2, 8.1, and 0.37, respectively. The removal rates were respectively 87.7%, 75.6%, 95.1%, and 90.1%, 85.6%, and 94.2%, and the average particle size of the particles reached 740 μm for R1 and 791 μm for R2. The results showed that for the same running time, the effluent NO3--N concentration and TP concentration in R2 were lower than those in R1. In the later stage of operation, the ratio of denitrifying phosphorus-accumulating organisms (DPAO) to total phosphorus-accumulating organisms (PAOs) in R1 and R2 increased from an initial 11.17% to 25.47% and 34.08%, respectively. Compared with the one influent-aeration operation strategy, the multiple influent-aeration operation strategy had a lower concentration of NO3--N in the initial stage of the startup, the PAOs received less impact, the DPAO enrichment was better, the phosphorus removal performance was better, and it helped to form aerobic granular sludge.

Temporal Anaerobic Effect on Aerobic Granular Sludge with Intermittent Influent-Intermittent Aeration

To initiate the domestic sewage aerobic granular sludge (AGS) process, the experiment is operated by intermittent influent-effluent aeration to reduce the concentration of nitrate and the inhibition of PAO, and realize granulation by phosphate precipitation and positive electricity particles generated during phosphorus removal. The sludge from a sewage treatment plant is inoculated into the SBR reactors R1, R2, R3, and R4, for durations of 30, 60, 90, and 120 min total anaerobic time. This was used to study the effect of anaerobic time on the aerobic granular sludge system in domestic sewage. The experiment shows that reactors R1, R2, R3, and R4 are started successfully with 56, 48, 39, and 35 days, respectively. After 105 days of the operation, the respective average particle sizes reached 750, 764, 791, and 650 μm. During the operational period, at the 43rd and 47th day, phosphorus removal performance deteriorated in R1 and R2, and it recovered after the anaerobic time was extended to 90 min. The effect of nitrogen and phosphorus removal in R3 is good; at the 63-77 day the granular sludge in R4 disintegrates, and the effect of nitrogen and phosphorus removal and DPAO enrichment is decreased. During the later stage of operation, the effluent in R1, R2, R3, and R4 reaches the IA standard of the discharge standard of pollutants for municipal wastewater treatment plant. The results show that a long anaerobic time can quickly achieve granulation, however the particles easily disintegrate during a long-term operation. Longer anaerobic time can reduce the inhibition of phosphorus accumulating organisms release phosphorus by nitrate, help enrich DPAO, and obtain a better nitrogen and phosphorus removal effect.

Improving methane production from algal sludge based anaerobic digestion by co-pretreatment with ultrasound and zero-valent iron

Resource recovery using algal sludge harvested from algal bloom has aroused broad interest. The present study investigated the methane production potential of algal sludge subjected to co-pretreatment with zero-valent iron and ultrasound. Results indicated that the combined zero-valent iron and ultrasound pretreatments induce algal cell wall disruption. Chlorophyll-a concentrations decreased by 14.17%, 25.20%, 35.77%, 45.05%, 61.07%, and 71.52% at zero-valent iron concentrations of 0, 1, 2, 5, 10, and 20 g of zero-valent iron/g of total solid, respectively, after ultrasound treatment for 30 min. Soluble chemical oxygen demands increased 5.22, 8.51, 9.85, 5.52, 11.94, and 9.40 times of corresponding original levels, respectively. After anaerobic digestion for 37 days, accumulative methane production was 30.39, 37.11, 38.06, 42.52, 49.27, 48.93, and 60.84 L CH4/kg total chemical oxygen demand of algae in Reactors R1–R7, respectively. Methane production constantly increased with zero-valent iron dosage, and the highest methane production was achieved at 20 g of zero-valent iron/g of algal total solid. Methane production in all conditions tested fitted to the one-substrate model. Model analysis indicated that hydrolysis coefficient and the dewaterability of algae increased with zero-valent iron dosage. The present study indicated that a pretreatment method combining zero-valent iron and ultrasound may be developed as an effective resource recovery technology for algal sludge treatment.

Availability of nutrients, removal of nicotine, heavy metals and pathogens in compounds obtained from smuggled cigarette tobacco compost associated with industrial sewage sludge

This study evaluated the chemical and microbiological properties of the compost obtained from the tobacco of smuggled cigarettes (SCT) and industrial sewage sludge (ISS). The composting was carried out in three reactors from different combinations of residues. The compost was analyzed to verify the percentage of nicotine removal, heavy metals, nutrient content and the inactivation of pathogenic microorganisms. The concentration of heavy metals: Ni, Cd, Cr, Pb, Cu, Zn, Fe and Mn in the composts obtained from the three reactors was below the values set for their use in soils. The NPK content ranged between 8.31% and 12.43%, indicating that the compost produced can add nutritional benefits to the plants. The nicotine removal, 72.6% (R1), 96.4% (R2) and 99.6% (R3) indicated efficiency of the composting process in reactors in the degradation of this substance. The results of pathogenic microorganism analysis showed that the three composts obtained from reactors R1, R2 and R3 met the sanitation standards for agricultural use according to the normative of maximum limits of contaminants allowed in organic compounds. These results show that the treatment of SCT and ISS by the process of composting in reactors may be an ecologically viable alternative.

Improving the energy balance of ethanol industry with methane production from vinasse and molasses in two-stage anaerobic reactors

Abstract Thermophilic anaerobic digestion is a viable option for processing sugarcane vinasse that recovers energy in the form of methane. However, restarting real-scale vinasse-treating reactors, at the resumption of the sugarcane harvest season, can lead to difficulties, making it desirable to keep them in continuous operation in the off-season. Thus, was evaluated the thermophilic anaerobic conversion of sugarcane vinasse in a two-stage upflow anaerobic sludge blanket (UASB) reactor (reactors R1 and R2), employing sugarcane molasses in the off-season for methane production, followed again by vinasse in the following harvest season. UASB reactor R2 yielded a higher methane percentage in biogas and higher volumetric methane production rates and methane yield than R1, accounting for a 58% increase in energy production in the two-stage system compared to the single-stage system using vinasse. It is observed that the molasses is an important source of carbon for the energy production using the thermophilic UASB reactors (18.01 MJ L−1 molasses), compared to alcoholic fermentation (8.30 MJ L−1 molasses). The methane produced in the reactors system (R1 + R2), after the off-season, can generate 5.1 kWh d−1 per m3 of vinasse, or 17% of the electricity needed to process a ton of sugarcane.

REATORES BIOLÓGICOS EM BATELADAS SEQUENCIAIS COM E SEM MATERIAL SUPORTE PARA REMOÇÃO SIMULTÂNEA DE NITROGÊNIO E FÓSFORO DE ESGOTO SANITÁRIO

Em corpos d’água sujeitos a problemas de eutrofização, a remoção biológica de nutrientes (RBN) assume grande importância. A combinação de vantagens da tecnologia do reator sequencial em batelada com sistema de biomassa fixa em um reator de biofilme de leito móvel (MBBR) é uma opção interessante na remoção de nitrogênio e fósforo em esgoto sanitário. O presente trabalho teve como objetivo comparar a eficiência de remoção de nitrogênio e fósforo de dois reatores (R1 e R2) operados em bateladas sequenciais, sendo que em um deles utilizou-se material suporte. Foi observada uma diminuição na concentração de matéria orgânica no efluente de ambos os reatores. As concentrações de NTK e fósforo total efluentes, em alguns momentos, foram maiores do que as afluentes. As maiores eficiências de nitrogênio amoniacal foram 47% e 52%, para os reatores R1 e R2, respectivamente. Com relação ao Ortofosfato, as eficiências máximas foram 47% e 58%, para os reatores R1 e R2, respectivamente. Em relação à quantidade de biomassa aderida ao meio suporte, a mesma foi baixa. Houve maior formação de biofilme na parte interior do material suporte, devido à força de cisalhamento provocada pelas hélices do agitador presente no reator. Os reatores se apresentaram ainda em fase de adaptação, pois somente foi observada uma remoção após algumas semanas de operação. A remoção no reator R2 mostrou-se mais significante em relação aos parâmetros analisados, porém ambos os reatores permaneceram numa faixa aproximada, levando em conta as eficiências.