Volatile Solids Research Articles

Study on the mechanism of action of methane production by co-fermentation of sludge and lignite.

To improve the methanogenic efficiency of lignite anaerobic fermentation and explore innovative approaches to sludge utilization, a co-fermentation technique involving lignite and sludge was employed for converting biomass into biomethane. Volatile suspended solids were introduced as a native enrichment of the sludge and mixed with lignite for fermentation. The synergistic fermentation mechanism between sludge and lignite for biomethane production was analyzed through biochemical methane potential experiments, measurement of various parameters pre- and post-fermentation, observation of bacterial population changes during the peak of reaction, carbon migration assessment, and evaluation of rheological characteristics. The results showed that the addition of sludge in the anaerobic fermentation process improved the microorganisms' ability to degrade lignite and bolstered biomethane production. Notably, the maximum methane production recorded was 215.52mL/g-volatile suspended solids, achieved at a sludge to coal ratio of 3:1, with a synergistic growth rate of 25.37%. Furthermore, the removal rates of total suspended solids, and total chemical oxygen demand exhibited an upward trend with an increasing percentage of sludge in the mixture. The relative abundance and activity of the methanogens population were found to increase with an appropriate ratio of sludge to lignite. This observation confirmed the migration of carbon between the solid-liquid-gas phases, promoting enhanced system affinity. Additionally, the changes in solid-liquid phase parameters before and after the reaction indicated that the addition of sludge improved the system's degradation capacity. The results of the study hold significant implications in realizing the resource utilization of sludge and lignite while contributing to environmental protection endeavors.

Optimizing Biogas Generation from Blends of Sugarcane Bagasse

Renewable energy has been the alternative source to global energy scarcity which involves renewable resources as more emphasis been put to prospective ways of converting agricultural wastes into energy to meet both the local and global demands.This work analyzed the use of sugarcane bagasse as substrate in biogas production as well as its codigestion with cow dung and chicken droppings. Seven digesters each of 2.5 litres capacity were charged in a ratio of 1:3 solids to liquid for a retention period of 30 days within a temperature range of 25-32 oC was used. Digester A contained 100 % bagasse, B contained 100 % cow dung, C 100 % chicken droppings, D contained 50 % bagasse and 50 % cow dung, E contained 50 % bagasse and 50 % chicken droppings, F contained 70 % bagasse and 30% cow dung and 70 % bagasse and 30 % chicken droppings for digester, G. Proximate and microbial analysis of the spent slurry were carried out. The result shows that sample C has the highest volatile solids and protein content of 56.68 % and 10.01 %. Biogas production was observed to be higher in digester C with cumulative gas yield of 3228.3 cm3 then digester B with 2816.6 cm3 and Digester A had the least gas yield of 681.4 cm3. Lightening test was observed by passage over limewater which result in catching fire except on digester C. Methane and other traces of gases test using gas analyzer shows 61.3 % methane with the least having 46.7 % methane on digester B and C. Pseudomonas spp, Entrobacter aerogenes and Staphylococcus aureus were found to be dominant in almost all the digesters. Further research is required to investigate large volume production and to improve gas storage techniques.

Mechanism of ball milling pretreatment to improve the anaerobic digestion performance and energy conversion efficiency of corn straw

In this study, the effects of ball-milling (BM) pretreatment on the anaerobic digestion (AD) performance and energy conversion efficiency of corn straw (CS) were explored. The AD testing was conducted by varying BM times (0–120 min) and TS (4–10 %). The results showed that BM pretreatment increased microbial and enzyme accessibility to the CS and facilitated the hydrolytic acidification process of AD. The peak concentration of volatile fatty acids (VFAs) (5325.69 mg/L) and chemical oxygen demand (COD) (14524 mg/L) were increased, resulting in more substrates available for methanogenic bacteria. The lag phase time was shortened (37.41–56.12 %) and the cumulative methane production was increased (45.63–104.11 %). Accelerated rate of total ammonia nitrogen (TAN) release resulted in increased buffering capacity of the digestion system. Reduced the initial density of the digestive slurry (6.91–9.58 %) and altered the water distribution (maximum increase in free water content to 70.4 %), which facilitated the agitation of the AD process. Excessive BM times (>60 min) and TS (>8%) are not recommended. The BM60-6 presented the highest volatile solids (VS) removal (78.79 %), cellulose degradation (92.07 %) and biochemical methane potential (BMP) (309.69 mL/g VS). The BM pretreatment also improved the rheological characteristics of digestive slurry and reduced the stirring power consumption of the AD process. The BM60-6 showed the largest net energy benefit (28.2101 KJ/g VS) and net residual value (0.5000), and the high energy input of the pretreatment was balanced. This discovery breaks the conventional wisdom that mechanical pretreatment is meaningless because of higher power consumption.

Impact of Thermal Pretreatment on the Physicochemical Characteristics and Biomethane Yield Potential of Solid Slaughter Waste from High-Throughput Red Meat Abattoirs Valorized as a Potential Feedstock for Biogas Production

Rapid urbanization worldwide results in high demand for meat products, which in turn result in high numbers of animals being slaughtered for human consumption to meet food security demands, especially in low-income countries such as South Africa. The waste produced during slaughtering can serve as feedstock for biogas production. This study aims to determine the impacts of pasteurization and sterilization pre-treatments on high-throughput red meat abattoir solid slaughter waste’s physicochemical properties and biomethane yield when used as a feedstock for biogas production. Abattoir solid slaughter waste was collected from 45 high-throughput red meat abattoirs across South Africa and the various physicochemical properties were determined using standard methods, along with the impact of sterilization and pasteurization on red meat abattoir waste. Biomethane yield analysis was performed using AMPTS II with a hydraulic retention time of 40 days. Pasteurization and sterilization pretreatment was seen to increase physicochemical parameters such as pH, volatile solids, total solids, carbon, and nitrogen analyzed in all samples. Pasteurization and sterilization were also seen to increase biomethane yield, where methane production ranged from 610.67 Nml to 1756.30 Nml, 1592.20 Nml to 3319.30 Nml, and 949.57 Nml to 3297.87 Nml for untreated, sterilized, and pasteurized samples, respectively. There was no significant difference (p < 0.05) observed in the effect pasteurized and sterilized samples had on physicochemical properties and biomethane yield. It can be concluded that pasteurization and sterilization enhance the bioavailability of the physicochemical properties and biomethane yield of red meat solid slaughter waste when valorized as feedstock for biogas production.

Enhancing kitchen waste anaerobic digestion by recycled aluminum industry waste: Alkali treatment and potential electron transfer mechanism

Kitchen waste has become a significant environmental concern worldwide. Red mud, an industrial solid waste characterized by its porous structure and high iron oxide content, exhibits potential as a conductive conduit in the direct interspecies electron transfer (DIET) pathway. In this study, red mud pretreatment of kitchen waste was conducted to enhance anaerobic digestion (AD). The effect and mechanism of enhancing kitchen waste AD by red mud pretreatment was studied for the first time. Results indicated that red mud pretreatment could accelerate the hydrolysis of organic compounds and alleviate the acid inhibition. Consequently, the methane production rate was increased from 260.7 mL/g VS to 402.3 mL/g VS, i.e., up to 54.3%. And volatile solids removal efficiency was increased from 53.9% to 73.1%, i.e., up to 35.6%. Furthermore, microbial community analysis revealed the enrichment of electrochemically active bacteria (Synergistaceae), acetogenic bacteria (Syntrophomonadaceae) and methanogens (Methanobacterium and Methanosarcina), which played essential roles in interspecies hydrogen transfer (IHT) and DIET. This study showed that red mud pretreatment has the potential to enhance kitchen waste AD which contributes to carbon mitigation. It also threw the potential new insights to the relative mechanism.

BIOGAS PRODUCTION POTENTIAL FROM ANAEROBIC CO-DIGESTION OF FOOD WASTE AND ANIMAL MANURE

The potential of biogas production by the anaerobic codigestion (AcoD) of canteen food waste and animal manure was investigated using the biochemical methane potential assay (BMP). The BMP assay was conducted under thermophilic temperature of 35 °C in a batch process at digestion time of 40 d. Waste substrate mixture was digested at a fixed proportion of 1:1 with different animal manure as co-substrate. Maximum cumulative biogas production (418 ml g-1 VS) was achieved during codigestion of food waste with pig manure > chicken manure (408 ml g-1 VS) > goat manure (319 ml g-1 VS). Generally, all manure codigested reactors produced 1.01 to 1.34 times more biogas than food waste alone indicating the synergistic effect of codigestion on overall biogas productivity. With analogous increase in biogas production, manure amendment produced significant (p<0.05) substrate biodegradation in terms of total and volatile solids loss. The microbial load profile prior and post-AD revealed significant reduction (p<0.05)in microbial species suggestion that anaerobic digestion can be adopted as a method of waste treatment and hygienization.

Biodrying of municipal solid waste-correlations between moisture content, organic content, and end of the biodrying process time.

Biodrying refers to the decomposition of organic municipal solid waste (MSW) under aerobic conditions. This process usually lasts 14days and requires large amounts of air to be injected into the waste matrix. The efficiency of the biodrying process depends on several geotechnical parameters, including initial moisture content, initial organic content, bulk density, dry density, solid particle density, and porosity. To examine the potential influence of these parameters on the biodrying process, we analyzed 13 biodried MSW samples. The results revealed a strong positive linear relationship between the initial moisture content and the mass loss percentage. In the first three days of the biodrying process, the waste mass rapidly decreased; afterwards, the daily mass loss occurred at a less rapid, more constant rate. The established average mass removal ratio between the volatile solids and water was 1:6.38 with a standard deviation of 1.06. Dry and solid particle densities were preserved in all 13 experiments; thus, the corresponding void ratio remained unchanged. This finding suggests that the settlement and degradation of MSW that occur during the biodrying process did not significantly influence the airflow rate.

Enhancing microalgae biomass production: Exploring improved scraping frequency in a hybrid cultivation system

Recently, hybrid systems, such as those incorporating high-rate algal ponds (HRAPs) and biofilm reactors (BRs), have shown promise in treating domestic wastewater while cultivating microalgae. In this context, the objective of the present study was to determine an improved scraping frequency to maximize microalgae biomass productivity in a mix of industrial (fruit-based juice production) and domestic wastewater. The mix was set to balance the carbon/nitrogen ratio. The scraping strategy involved maintaining 1 cm wide stripes to retain an inoculum in the reactor. Three scraping frequencies (2, 4, and 6 days) were evaluated. The findings indicate that a scraping frequency of each 2 days provided the highest biomass productivity (18.75 g total volatile solids m−2 d−1). The species’ behavior varied with frequency: Chlorella vulgaris was abundant at 6-day intervals, whereas Tetradesmus obliquus favored shorter intervals. Biomass from more frequent scraping demonstrated a higher lipid content (15.45%). Extrapolymeric substance production was also highest at the 2-day frequency. Concerning wastewater treatment, the system removed 93% of dissolved organic carbon and ∼100% of ammoniacal nitrogen. Combining industrial and domestic wastewater sources to balance the carbon/nitrogen ratio enhanced treatment efficiency and biomass yield. This study highlights the potential of adjusting scraping frequencies in hybrid systems for improved wastewater treatment and microalgae production.

Degradation of Chloroquine by Ammonia-Oxidizing Bacteria: Performance, Mechanisms, and Associated Impact on N2O Production.

Since the mass production and extensive use of chloroquine (CLQ) would lead to its inevitable discharge, wastewater treatment plants (WWTPs) might play a key role in the management of CLQ. Despite the reported functional versatility of ammonia-oxidizing bacteria (AOB) that mediate the first step for biological nitrogen removal at WWTP (i.e., partial nitrification), their potential capability to degrade CLQ remains to be discovered. Therefore, with the enriched partial nitrification sludge, a series of dedicated batch tests were performed in this study to verify the performance and mechanisms of CLQ biodegradation under the ammonium conditions of mainstream wastewater. The results showed that AOB could degrade CLQ in the presence of ammonium oxidation activity, but the capability was limited by the amount of partial nitrification sludge (∼1.1 mg/L at a mixed liquor volatile suspended solids concentration of 200 mg/L). CLQ and its biodegradation products were found to have no significant effect on the ammonium oxidation activity of AOB while the latter would promote N2O production through the AOB denitrification pathway, especially at relatively low DO levels (≤0.5 mg-O2/L). This study provided valuable insights into a more comprehensive assessment of the fate of CLQ in the context of wastewater treatment.

The Fate of Soil Organic Carbon from Compost: A Pot Test Study Using Labile Carbon and 13c Natural Abundance

Recycled organic waste (OW) can be a valuable nutrient source for plant cultivation; however, knowledge is poor regarding its effect on soil carbon conservation, especially in the frame of organic-mineral fertilisation succession. In this study, four composts, green waste (GWC), anaerobically digested bio-waste (DC), sludge (SSC), and bio-waste (BWC), were compared (10 and 20 Mg volatile solids ha−1) in a ryegrass pot test over two growing cycles (112 + 112 days), along with an unamended control (Ctrl) and a chemical reference (Chem), with and without mineral nitrogen (N) fertilisation. At the end of the two growth cycles, the pot soil was analysed for total- (TOC) and labile-carbon (CL) as well as for 13C isotope natural abundance (δ13C and Δ13C vs. Chem). At day 112, the pot test showed that Ctrl and Chem gained poor TOC (8.48 g kg−1), lower than the compost at both 10 and 20 Mg volatile solids ha−1 (10.01 vs. 11.59 g kg−1). At day 224, a deep soil TOC depletion occurred in the pot soil treated with GWC, DC and BWC at both levels (-10 and -20). However, all the compost treatments showed more depleted soil d13C vs. the references, especially Chem, thus revealing relevant compost-derived carbon conservation. Regarding the compost treatments, the carbon management index (CMI) increased over time, indicating high soil functionality, also showing a good relationship with δ13C, suggesting a probable increase in relative lignin which could have been linked to carbon conservation and increased functionality.

New insights on destruction mechanisms of waste activated sludge during simultaneous thickening and digestion process via forward osmosis membrane

This study delved into the efficacy of sludge digestion and the mechanisms involved in sludge destruction during the implementation of forward osmosis process for sludge thickening and digestion (FO-MSTD). Utilizing a lab-scale FO membrane reactor for the thickening and digestion of waste activated sludge (WAS), the investigation explored the effects of sludge thickening and digestion in FO-MSTD processes using draw solutions of varying concentrations. The findings underscored the significance of hydraulic retention time (HRT) as a pivotal parameter influencing the swift thickening or profound digestion of sludge. Consequently, tailoring the HRT to specific processing objectives emerged as a key strategy for achieving desired treatment outcomes. In the investigation, the use of a 1 M NaCl draw solution in the FO-MSTD process showcased enhanced thickening and digestion capabilities. This specific setup raised the concentration of mixed liquor suspended solids (MLSS) to over 30 g/L and achieved a 42.7% digestion efficiency of mixed liquor volatile suspended solids (MLVSS) within an operational timeframe of 18 days. Furthermore, the research unveiled distinct stages in the sludge digestion process of the FO-MSTD system, characterized by fully aerobic digestion and aerobic-local anaerobic co-existing digestion. In the fully aerobic digestion stage, the sludge digestion rate exhibited a steady increase, leading to the breakdown of sludge floc structures and the release of a substantial amount of nutrients into the sludge supernatant. The predominant microorganisms during this stage were typical functional microorganisms found in wastewater treatment systems. Transitioning into the aerobic-local anaerobic co-existing digestion stage, both MLSS concentration and MLVSS digestion efficiency continued to rise, accompanied by a decreasing dissolved oxygen (DO) concentration. More organic matter was released into the supernatant, and sludge microbial flocs tended to reaggregate. The localized anaerobic environment within the FO-MSTD reactor fostered an increase in the relative abundance of bacteria with nitrogen and phosphorus removal functions, thereby positively impacting the mitigation of total nitrogen (TN) and total phosphorus (TP) concentrations in the sludge supernatant. The results of this research enhance comprehension of the advanced FO-MSTD technology in the treatment of WAS.

Enhanced methane production with co-feeding spent coffee grounds using spare capacity of existing anaerobic food waste digesters

With increasing coffee consumption worldwide, the efficient and sustainable management of spent coffee grounds (SCG) has become increasingly challenging. This study investigated the anaerobic co-digestion of small amounts of SCG with food waste (FW) at increasing co-feeding ratios of 1:100–1:10 (volatile solids basis) to assess the possibility of SCG treatment using the spare capacity of existing anaerobic digesters. Co-feeding SCG increased methane production compared to FW mono-digestion in the tested range of co-feeding ratios without compromising process stability. Methane yield did not further increase when the SCG/FW ratio increased above 4%, and process failure occurred at a 1:10 co-feeding ratio without trace element supplementation. The enhanced methanogenic performance was attributed to increased protein removal efficiency, which was potentially related to the promotion of peptide hydrolysis. The overall results suggest that co-feeding appropriate small amounts of SCG to FW digesters can be a realistic sustainable option for SCG management.

Machine learning methods for the modelling and optimisation of biogas production from anaerobic digestion: a review.

Biogas plant operators often face huge challenges in the monitoring, controlling and optimisation of the anaerobic digestion (AD) process, as it is very sensitive to surrounding changes, which often leads to process failure and adversely affects biogas production. Conventional implemented methods and mechanistic models are impractical and find it difficult to model the nonlinear and intricate interactions of the AD process. Thus, the development of machine learning (ML) algorithms has attracted considerable interest in the areas of process optimization, real-time monitoring, perturbation detection and parameter prediction. This paper provides a comprehensive and up-to-date overview of different machine learning algorithms, including artificial neural network (ANN), fuzzy logic (FL), adaptive network-based fuzzy inference system (ANFIS), support vector machine (SVM), genetic algorithm (GA) and particle swarm optimization (PSO) in terms of working mechanism, structure, advantages and disadvantages, as well as their prediction performances in modelling the biogas production. A few recent case studies of their applications and limitations are also critically reviewed and compared, providing useful information and recommendation in the selection and application of different ML algorithms. This review shows that the prediction efficiency of different ML algorithms is greatly impacted by variations in the reactor configurations, operating conditions, influent characteristics, selection of input parameters and network architectures. It is recommended to incorporate mixed liquor volatile suspended solids (MLVSS) concentration of the anaerobic digester (ranging from 16,500 to 46,700mg/L) as one of the input parameters to improve the prediction efficiency of ML modelling. This review also shows that the combination of different ML algorithms (i.e. hybrid GA-ANN model) could yield better accuracy with higher R2 (0.9986) than conventional algorithms and could improve the optimization model of AD. Besides, future works could be focused on the incorporation of an integrated digital twin system coupled with ML techniques into the existing Supervisory Control and Data Acquisition (SCADA) system of any biogas plant to detect any operational abnormalities and prevent digester upsets.

Self-cultivating anammox granules for enhancing wastewater nitrogen removal in nitrification–denitrification flocculent sludge system

The feasibility of self-cultivating anammox granules for enhancing wastewater nitrogen removal was investigated in a nitrification–denitrification flocculent sludge system. Desirable nitrogen removal efficiency of 84 ± 4 % was obtained for the influent carbon to nitrogen ratio of 1–1.3 (NH4+-N: 150–200 mg N/L) via alternate anaerobic/oxic/anoxic mode. Meanwhile, some red granular sludge was formed in the system. The abundance and activity of anaerobic ammonia oxidation bacteria (AnAOB) increased from ‘not detected’ in seed sludge to 0.57 % and 29.4 ± 0.7 mg N/(g mixed liquor volatile suspended solids·h) in granules, respectively, suggesting successful cultivation of anammox granules. Furthermore, some denitrifying bacteria with capability of partial denitrification were enriched, such as Candidatus Competibacter (2.45 %) and Thauera (5.75 %), which could cooperate with AnAOB, facilitating AnAOB enrichment. Anammox was dominant in nitrogen removal with the contribution to nitrogen removed above 68.8 ± 0.3 %. The strategy of self-cultivating anammox granules could promote the application of anammox.

The impact of salinity on biomethane production and microbial community in the anaerobic digestion of food waste components

Food waste represents a valuable resource potential for the production of advanced biofuels, including biomethane. This study systematically assessed the impact of salt on biomethane production from different components of food waste. The highest biomethane yields of 258.89 ± 10.96, 337.52 ± 16.36, and 448.49 ± 23.375 mL/g volatile solids (equivalent to biodegradability indexes of 75.75%, 88.92% and 92.66%) were achieved from cellulose-rich, starch-rich and protein-rich components, respectively, at a salt concentration of 3 g NaCl/L. The biomethane yield was improved by 9.69–31.24% with low-concentration salt compared with no salt addition, but it was inhibited by high salinity. Inhibition induced by high salinity (15 g NaCl/L) on biomethane production followed the order of protein (15.50%) < starch (28.03%) < cellulose (42.92%). Co-digestion of different components effectively mitigated the inhibitory effect of salt on biomethane production. Microbial community analysis revealed that archaea were significantly affected by high salinity. With a high concentration of salt (15 g/L), acetoclastic methanogens (Methanosatea) predominated in the digestion of starch-rich components, whilst hydrogenotrophic methanogens (Methaonmassiliicoccus and Methanobacterium) predominated in the digestion of cellulose-rich and protein-rich components. Additionally, some salt-tolerant microorganisms (SC103, Thermovirga and Methanosarcina) were selectively enriched at high salinity.

Optimisation of Biogas Production in the Co-Digestion of Pre-Hydrodynamically Cavitated Aerobic Granular Sludge with Waste Fats

The characteristics of excess aerobic granular sludge, related to its structure and chemical composition, limit the efficiency of anaerobic digestion. For this reason, pre-treatment methods and compositions with other organic substrates are used. In earlier work, no attempt was made to intensify the methane fermentation of the excess aerobic granular sludge by adding fatty waste materials. The aim of the research was to determine the effects of co-digestion of pre-hydrodynamically cavitated aerobic granular sludge with waste fats on the efficiency of methane fermentation under mesophilic and thermophilic conditions. The addition of waste fats improved the C/N ratio and increased its value to 19. Under mesophilic conditions, the highest effects were observed when the proportion of volatile solids from waste fats was 25%. The amount of biogas produced increased by 17.85% and CH4 by 19.85% compared to the control. The greatest effects were observed in thermophilic anaerobic digestion at 55 °C, where a 15% waste fat content in volatile solids was ensured. This resulted in the production of 1278.2 ± 40.2 mL/gVS biogas and 889.4 ± 29.7 mL/gVS CH4. The CH4 content of the biogas was 69.6 ± 1.3%. The increase in biogas and CH4 yield compared to pure aerobic granular sludge anaerobic digestion was 34.4% and 40.1%, respectively. An increase in the proportion of waste fats in the substrate had no significant effect on the efficiency of methane fermentation. Strong positive correlations (R2 &gt; 0.9) were observed between biogas and CH4 production and the C/N ratio and VS concentration.

Effect of alkaline pretreatment on the characteristics of barley straw and modeling of methane production via codigestion of pretreated straw with sewage sludge

Straw pretreatment enhances the cellulose accessibility and increases the methane yield from anaerobic digestion. This study investigated the effects of alkali pretreatments with different chemical agents (NaOH, KOH, and Na2CO3) on the physicochemical and thermal characteristics of barley straw, as well as methane production from codigestion with sewage sludge. Artificial neural network modeling with a feedforward neural network (FFNN) and slime mold optimization (SMO) techniques were used to predict methane production. NaOH pretreatment was shown to be the best pretreatment for removing hemicellulose and lignin and for increasing the cellulose accessibility. Moreover, there was a 2.57-fold higher level of methane production compared to that from codigestion with untreated straw. The removal ratios for the total solids, volatile solids, and chemical oxygen demand reached 59.3, 67.2, and 73.4%, respectively. The modeling results showed that the FFNN-SMO method can be an effective tool for simulating the methane generation process, since training, validating, and testing produced very high correlation coefficients. The FFNN-SMO accurately predicted the amount of methane produced, with an R2 of 0.998 and a 3.1×10-5 root mean square error (RMSE).

Study of helminth eggs (Ascaris suum) inactivation by anaerobic digestion and electrochemical treatment

Background The use of insufficiently treated wastewater or Faecal sludge in agriculture raises concerns because of the pathogen content. Helminth eggs (HE) are one of the most crucial pathogens for ensuring public health and safety. Widely used disinfection treatment methods do not guarantee the complete inactivation of helminth eggs. The current study evaluated the effectiveness of anaerobic digestion and electrochemical process on helminth (Ascaris suum) egg inactivation. Methods Lab-scale biochemical methane potential (BMP) assay was conducted by spiking A. suum eggs in a serum bottle. Total solid (TS), volatile solid (VS), pH, biogas production and its composition, and volatile fatty acids (VFA) were analyzed along with A. suum inactivation every third day for the initial 15 days and fifth day for 45 days. In the second set of experiments, a hypochlorite (4700 ppm) solution was generated by electrolysis of aqueous NaCl solution in a membrane-less electrochemical cell. The hypochlorite was diluted (940, 470, 235, and 156ppm) in wastewater, spiked with A. suum eggs and then examined for inactivation at regular intervals. Results The results of the anaerobic digestion treatment documented 98% inactivation of A. suum eggs (0.15 eggs/mL) in 35 days and remained at 0.14 eggs/mL until day 45. Correlation analysis revealed a positive relationship between non-viable eggs and pH and a negative relationship with all the other parameters. Electrochemical treatment achieved 10% inactivation at 940 ppm concentration in 24h. Conclusions This study revealed that the inactivation of A. suum eggs by anaerobic digestion or electrochemical treatment is a combined effect of more than one parameter.

Enhancing Single- and Two-Stage Anaerobic Digestion of Thickened Waste-Activated Sludge through FNA-Heat Pretreatment

This study aimed to investigate the effect of combined Free Nitrous Acid (FNA)-Heat (i.e., FNH) pretreatment on single- and two-stage anaerobic digestion (AD) of thickened waste-activated sludge (TWAS). Single-stage AD was conducted in batches, while two-stage AD involved acidogenic fermentation under semi-continuous flow followed by batch methanogenesis. FNH pretreatment was applied before the acidogenic stage, using 1.4 mg HNO2-N/L FNA concentration at 25 °C, 37 °C, and 60 °C for 24 h. Among the scenarios, the most promising results were observed with two-stage AD fed with FNH-pretreated TWAS at 60 °C, showing higher COD solubilization and a reduction in volatile solids. Combined FNA-Heat pretreatment in two-stage AD yielded elevated methane production (363–415 mL CH4/g VS added) compared to single-stage digestion. Methane yields from FNA-Heat pretreated single-stage ranged from 332 to 347 mL CH4/g VS added, contrasting with 212 mL CH4/g VS added for untreated TWAS. Methane generation commenced early in both untreated and pretreated samples, attributed to soluble substrate abundance.

A novel co-metabolic mode with Spirulina powder in enhancing the anaerobic degradation of typical nitrogen heterocyclic compounds

ABSTRACT Spirulina powder emerged as a novel and suitable co-metabolism substance significantly enhancing the anaerobic degradation of specific nitrogen heterocyclic compounds. On the addition of 1.0 mg/L of Spirulina powder, the reactor demonstrated optimal degradation efficiency for quinoline and indole, achieving ratios of 99.77 ± 1.83% and 99.57 ± 1.98%, respectively. Moreover, the incorporation of Spirulina powder resulted in increased concentrations of mixed liquor suspended solids, mixed liquor volatile suspended solids, proteins, and polysaccharides in anaerobic sludge. In addition, Spirulina powder led to reduced levels of Acinetobacter and enriched Aminicenantes genera incertae sedis, Levilinea, and Longilinea. The analysis of the archaeal community structure confirmed that the addition of Spirulina powder increased archaeal sequences, fostering greater richness and diversity in the archaeal community.