Sustainable Agro-Food Industrial Wastewater Treatment Using High Rate Anaerobic Process

Wastewater treatment in lagoons: A systematic review and a meta-analysis

This study has carried out a systematic review of 36 scientific papers (reporting 63 case studies) published in the last 15 years about the treatment of industrial, agri-food and municipal wastewater in lagoons. A concentration of studies from a few countries (Italy, Algeria and Iran) and about municipal wastewater (70% of papers) was revealed by the bibliographic analysis. Aeration was supplied in more than 50% of case studies; the storage capacity of lagoons (adopted as a measure of size) was extremely variable (over seven orders of magnitude), while their depth was generally lower than a few metres. The efficiency of lagoon treatments at removing COD was in a wide range (25-98%). Very few studies analysed the energy intensity of treatments in lagoons. The meta-analysis applied to a further selection of 10 papers with 29 case studies revealed significant differences in pH and dissolved oxygen concentration, due to aeration or type of treated wastewater. Treatment efficiency was higher in aerated lagoons compared to non-aerated systems, and did not depend on the type of treated wastewater. Based on the analysis of the reviewed papers, an urgent research need on this topic arises, mainly due to the oldness of most analysed studies. Practical suggestions are given to optimise the depuration performances of lagoons: (i) application of intermittent and night aeration; (ii) reduced air flow rates; (iii) adaptation of microbial biomass to high contents of inhibiting compounds in wastewater; (iv) construction of baffles to keep the planned hydraulic retention time avoiding short-circuit; (v) integration of lagoons with other treatments (e.g., constructed wetlands); (vi) ferti-irrigation of crops with lagoon effluents rather than disposal into water bodies.

Bioelectrochemical systems (BESs) for agro-food waste and wastewater treatment, and sustainable bioenergy-A review

Producing food by farming and subsequent food manufacturing are central to the world's food supply, accounting for more than half of all production. Production is, however, closely related to the creation of large amounts of organic wastes or byproducts (agro-food waste or wastewater) that negatively impact the environment and the climate. Global climate change mitigation is an urgent need that necessitates sustainable development. For that purpose, proper agro-food waste and wastewater management are essential, not only for waste reduction but also for resource optimization. To achieve sustainability in food production, biotechnology is considered as key factor since its continuous development and broad implementation will potentially benefit ecosystems by turning polluting waste into biodegradable materials; this will become more feasible and common as environmentally friendly industrial processes improve. Bioelectrochemical systems are a revitalized, promising biotechnology integrating microorganisms (or enzymes) with multifaceted applications. The technology can efficiently reduce waste and wastewater while recovering energy and chemicals, taking advantage of their biological elements' specific redox processes. In this review, a consolidated description of agro-food waste and wastewater and its remediation possibilities, using different bioelectrochemical-based systems is presented and discussed together with a critical view of the current and future potential applications.

Valorisation through Lactic Fermentation of Industrial Wastewaters from a Bean Blanching Treatment

In recent years, scientific research and industries have been focusing on the application of biological treatments aimed at imparting functional properties to waste products from food industries according to the principles on which the circular economy model is based, namely, the recovery, valorisation, and reuse of wastes. This work aimed at exploring the possibility of valorising waters from the blanching process of dried navy beans through lactic acid fermentation using Lacticaseibacillus paracasei CBA L74 as a starter. Two samples at different solid concentrations (0.75 °Bx and 1.25 °Bx) were fermented, and, in both cases, a bacterial load of 8 Logs and a lactic acid concentration of approximately 1.3 g/L were reached, despite the lack of nutrients. An unusual pH trend, characterised by an initial decrease and unexpected final rise, was observed during the fermentation of both samples: simultaneously, an increase in protein content was observed, suggesting that the proteolytic action of the microorganism could be responsible for the release of pH-increasing substances. In both cases, a slight increase in total polyphenols (approximately 23.3–33.72%) and flavonoids (approximately 42.3–52%) due to fermentation was observed, with a corresponding improvement in antioxidant capacity (approximately 25.32–37.72%). A significant increase in saponin concentration was determined for the most concentrated blanching water (from 2.87 ± 0.28 to 6.68 ± 0.69 mgOAE/mL), leading to an improvement in foaming properties and an enhanced capacity to produce stable emulsions. The obtained results confirmed the possibility of reducing water consumption from blanching operations, as well as finding valorisation opportunities for this side stream through a safe and inexpensive fermentation treatment.

Degradation of Agro-Industrial Wastewater Model Compound by UV-A-Fenton Process: Batch vs. Continuous Mode

The degradation of a model agro-industrial wastewater phenolic compound (caffeic acid, CA) by a UV-A-Fenton system was investigated in this work. Experiments were carried out in order to compare batch and continuous mode. Initially, batch experiments showed that UV-A-Fenton at pH 3.0 (pH of CA solution) achieved a higher generation of HO•, leading to high CA degradation (>99.5%). The influence of different operational conditions, such as H2O2 and Fe2+ concentrations, were evaluated. The results fit a pseudo first-order (PFO) kinetic model, and a high kinetic rate of CA removal was observed, with a [CA] = 5.5 × 10−4 mol/L, [H2O2] = 2.2 × 10−3 mol/L and [Fe2+] = 1.1 × 10−4 mol/L (kCA = 0.694 min−1), with an electric energy per order (EEO) of 7.23 kWh m−3 order−1. Under the same operational conditions, experiments in continuous mode were performed under different flow rates. The results showed that CA achieved a steady state with higher space-times (θ = 0.04) in comparison to dissolved organic carbon (DOC) removal (θ = 0−0.020). The results showed that by increasing the flow rate (F) from 1 to 4 mL min−1, the CA and DOC removal rate increased significantly (kCA = 0.468 min−1; kDOC = 0.00896 min−1). It is concluded that continuous modes are advantageous systems that can be adapted to wastewater treatment plants for the treatment of real agro-industrial wastewaters.

Optimization of operating parameters for biogas production using two-phase bench-scale anaerobic digestion of slaughterhouse wastewater: Focus on methanogenic step

The objective of the present study was an optimization of operating parameters and the performance of the methanogenesis reactor in phased anaerobic digestion (AD) of slaughterhouse wastewater at 37.5°C. Accordingly, the feedstock of the methanogenic reactor was effluent from the hydrolytic-acidogenic reactor operating at HRT of 3-days and OLR of 1789 mg/L. The methanogenesis phase was also investigated at different hydraulic retention time (HRT) values ranging from 12 to 3 days at 3-day intervals, and organic loading rates (OLR) of 149, 199, 298, and 596 mg of COD/L. The methanogenesis reactor effluent concentrations of TN, TP, PO4- 3, SO4- 2, and S2- 2 were ranging between 424-464, 83-117, 63-86, 130-197, and 0.98-1.02 mg/L, respectively. The removal efficiencies of TN and TP were vary from 10-17% to 17-21%, respectively. The average biogas production was 125 ± 16, 150 ± 10, 185 ± 4, and 154 ± 17 mL at HRT of 12, 9, 6, and 3 days, respectively. Methane quality (%) and yield (mg/L of COD) were 55-67% and 0.02-0.03, respectively. Furthermore, the average stability indicator parameter values of (total volatile fatty acid (TVFA) = 520 ± 19 mg/L, total alkalinity (TotA) = 1424 ± 10 mg/L, TVFA:TotA. Ratio = 0.36, salinity = 1172 mg/L, pH = 6.92) and performance indicator parameters removal efficiency (RE) for (chemical oxygen demand (COD) = 81%, volatile solid (VS) RE = 95%, biogas production = 185 ± 4 mL, methane yield = 0.03 per mg COD consumed) were achieved at HRT of 6 days and OLR of 298 mg of COD/L. Low removal efficiencies of TP and TN at all HRT/OLR were observed for the methanogenic reactor signifying further treatment system.

Biotreatment Potential and Microbial Communities in Aerobic Bioreactor Systems Treating Agro-Industrial Wastewaters

The thriving agro-industry sector accounts for an essential part of the global gross domestic product, as the need for food and feed production is rising. However, the industrial processing of agricultural products requires the use of water at all stages, which consequently leads to the production of vast amounts of effluents with diverse characteristics, which contain a significantly elevated organic content. This fact reinforces the need for action to control and minimize the environmental impact of the produced wastewater, and activated sludge systems constitute a highly reliable solution for its treatment. The current review offers novel insights on the efficiency of aerobic biosystems in the treatment of agro-industrial wastewaters and their ecology, with an additional focus on the biotechnological potential of the activated sludge of such wastewater treatment plants.

Photocatalytic nanohybrid membranes for highly efficient wastewater treatment: A comprehensive review

Wastewater is inevitably generated from human activities as part of the life cycle chain that potentially damages the environment. The integration of photocatalytic reaction and membrane separation for wastewater treatment has gained great attention in recent studies. However, there are still many technical limitations for its application such as toxic metal release, catalyst deactivation, fouling/biofouling, polymer disintegration, and separation performance decline. Different types, combinations, and modifications of photocatalysts material combined with membranes such as semiconductor metal oxides, binary/ternary hybrid metal oxides, elemental doped semiconductors, and metal-organic frameworks (MOFs) for improving the performance and compatibility are presented and discussed. The strategies of incorporating photocatalysts into membrane matrix for pursuing the most stable membrane integrity, high photocatalytic efficiency, and excellent perm-selectivity performance in the very recent studies were discussed. This review also outlines the performance enhancement of photocatalytic membranes (PMs) in wastewater treatment and its potential for water reclamation. Photocatalysts enhanced membrane separation by inducing anti-fouling and self-cleaning properties as well as antibacterial activity. Based on the reviewed study, PMs are possible to achieve complete removal of emerging contaminants and ∼99% reduction of bacterial colony that leading on the zero liquid discharge (ZLD). However, the intensive exposure of photo-induced radicals potentially damages the polymeric membrane. Therefore, future studies should be focused on fabricating chemically stable host-membrane material. Moreover, the light source and the membrane module design for the practical application by considering the hydrodynamic and cost-efficiency should be a concern for technology diffusion to the industrial-scale application.

Autonomous high-throughput in situ soil nitrogen flux measurement system

Nitrogen (N) behavior in soil is a major component of the global N cycle. Climate scientists seek to accurately measure N flux to the atmosphere, farmers want to maximize plant N uptake and reduce input costs, and industries land-applying wastewater must mitigate potential N leaching to drinking water supplies. The need to quantify denitrification rates of wastewater disposed of by vegetable processing and cheese making industries in Wisconsin drove the development of an autonomous high-throughput in situ sampling and analysis system for soil N flux. The system was deployed to six unique industry sites with different soil types for 7 days once per quarter and data collected continuously. Additional seasonal data collection allowed for the determination of system N mass balances. The system can deliver quality data under challenging conditions where staffing would be impractical and provide detailed information about soil gas emissions under a range of environmental conditions.

Insight into the Impacts and Removal Pathways of Perfluorooctanoic Acid (PFOA) in Anaerobic Digestion

Perfluorooctanoic acid (PFOA) that accumulates in wastewater and excess sludge interact with the anaerobes and deteriorate the energy recovery and pollutants removal performance in the anaerobic digestion (AD) system. However, the interaction between PFOA and microbial metabolism in the AD systems remains unclear. This study aimed to clarify the effects and mechanism of PFOA on the AD process as well as the removal pathways of PFOA in an AD system. The results showed that the methane recovery efficiency was inhibited by 7.6–19.7% with the increased PFOA concentration of 0.5–3.0 mg/L, and the specific methanogenesis activity (SMA) was inhibited by 8.6–22.3%. The electron transfer system (ETS) was inhibited by 22.1–37.3% in the PFOA-containing groups. However, extracellular polymeric substance (EPS) gradually increased due to the toxicity of PFOA, and the ratio of protein to polysaccharide shows an upward trend, which led to the formation of sludge aggregates and resistance to the toxic of PFOA. The PFOA mass balance analysis indicated that 64.2–71.6% of PFOA was removed in the AD system, and sludge adsorption was the main removal pathway, accounting for 36.1–61.2% of the removed PFOA. In addition, the anaerobes are proposed to have the potential to reduce PFOA through biochemical degradation since 10.4–28.2% of PFOA was missing in the AD system. This study provides a significant reference for the treatment of high-strength PFOA-containing wastes.

Energy Systems in the Food Supply Chain and in the Food Loss and Waste Valorization Processes: A Systematic Review

The intensity in energy consumption due to food production systems represents a major issue in a context of natural resources depletion and an increasing worldwide population. In this framework, at least a third of global food production is being lost or wasted. Moreover, about 38% of the energy embedded in total food production is being lost. Consequently, the assessment of energy consumption in food systems, and in food loss and waste valorization systems, is an increasing trend in recent years. In this line, this work presents a systematic review, selecting 74 articles from a search of 16,930 papers regarding the key words “energy assessment food”. The aim was to determine the current and historical trends in this field of research. Results pointed to a worldwide acceleration in trends since 2014, standing out in China and other Asian countries. Concerning the topics of the publications, energy consumption in the food sector is a research field which has existed since 1979. Moreover, the study of energy valorization systems using food loss and waste is an increasing trend since 2010. Additionally, publications focused on the water–energy–food nexus appeared firstly in 2014 and have grown exponentially. Moreover, life cycle assessment highlights as the most widespread methodology used.

Treatment of wastewater with high carbon-to-nitrogen ratio using a waterfall aeration biofilm reactor combined with sequencing batch reactor: Microbial community structure and metabolism analysis

A low-cost and high-efficiency waterfall aeration biofilm reactor (WABR) combined with a sequencing batch reactor (SBR) was established to treat wastewater with a C/N ratio of 50. Three WABR-SBR systems with different fillers were used. In the stable operation phase, the removal efficiency of chemical oxygen demand was R1 (approximately 99%), R2 (97-99%), and R3 (96-99%); the effluent concentration of NH₄⁺-N was 0.5 mg/L without nitrite or nitrate accumulation. High-throughput 16S rRNA sequencing revealed that the dominant phyla in the microbial community structure were Proteobacteria, Bacteroidetes, and Planctomycetes. Quantitative PCR was used to quantify the nitrification and denitrification gene expressions (Nitrobacter, nirS, and nirK) to evaluate the simultaneous nitrification and denitrification processes. Both anammox and denitrifying bacteria were abundant. Metagenomic annotation of genes that revealed the metabolic pathways of carbohydrates, amino acids, and the two dominant enzymes (GH and GT) provide valuable information for microbial ecology analysis.

Multi-Integrated Systems for Treatment of Abattoir Wastewater: A Review

Biological wastewater treatment processes such as activated sludge and anaerobic digestion remain the most favorable when compared to processes such as chemical precipitation and ion exchange due to their cost-effectiveness, eco-friendliness, ease of operation, and low maintenance. Since Abattoir Wastewater (AWW) is characterized as having high organic content, anaerobic digestion is slow and inadequate for complete removal of all nutrients and organic matter when required to produce a high-quality effluent that satisfies discharge standards. Multi-integrated systems can be designed in which additional stages are added before the anaerobic digester (pre-treatment), as well as after the digester (post-treatment) for nutrient recovery and pathogen removal. This can aid the water treatment plant effluent to meet the discharge regulations imposed by the legislator and allow the possibility for reuse on-site. This review aims to provide information on the principles of anaerobic digestion, aeration pre-treatment technology using enzymes and a hybrid membrane bioreactor, describing their various roles in AWW treatment. Simultaneous nitrification and denitrification are essential to add after anaerobic digestion for nutrient recovery utilizing a single step process. Nutrient recovery has become more favorable than nutrient removal in wastewater treatment because it consumes less energy, making the process cost-effective. In addition, recovered nutrients can be used to make nutrient-based fertilizers, reducing the effects of eutrophication and land degradation. The downflow expanded granular bed reactor is also compared to other high-rate anaerobic reactors, such as the up-flow anaerobic sludge blanket (UASB) and the expanded granular sludge bed reactor (EGSB).

Effects of brewery sludge on soil chemical properties, trace metal availability in soil and uptake by wheat crop, and bioaccumulation factor

Brewery sludge is the solid residue obtained from agro-industrial processing. It is possible to utilize the waste products in an environment friendly and economical way to replace mineral fertilizer due to its sufficient macronutrients and organic carbon content. However, its use is limited due to heavy metal concentration that may contaminate crops and then the food chain. The objective of this study was to assess the suitability of brewery sludge for using to grow bread wheat (Triticum aestivum L.) by determining the effect of brewery sludge (7 levels: 0, 3, 6, 9, 12 and 15 t ha⁻¹, and 1 recommended rate of NPS only) on soil chemical properties, bioaccumulation factor, and heavy metal absorption in the soil and in the bread wheat grain using a Randomized Blocks Design field experiment conducted at two sites during the 2018 cropping season. Amendment of brewery sludge at a rate of 15 t ha⁻¹ led to substantial variations in soil chemical properties except for Mg²⁺ content at both study sites. Concentrations of the studied heavy metals (except Zn in the soil) increased with increasing brewery sludge application rate in the soil and in the wheat grain. However, heavy metal uptake by wheat grain and heavy metal concentration in the soil were below the allowed limits. The bioaccumulation factor in the wheat grain was <1.0 for the studied heavy metals. The findings of the study suggest that brewery sludge at a rate of 15 t ha⁻¹ could be recommended due to its high nourishing effect for soil and for promoting nutritional quality of wheat crop and is safe for human consumption. However, since sludge application may lead to increase in the amount of trace metals in the soil-plant system, a long-term study is recommended.

The Role of Petrimonas mucosa ING2-E5AT in Mesophilic Biogas Reactor Systems as Deduced from Multiomics Analyses

Members of the genera Proteiniphilum and Petrimonas were speculated to represent indicators reflecting process instability within anaerobic digestion (AD) microbiomes. Therefore, Petrimonas mucosa ING2-E5AT was isolated from a biogas reactor sample and sequenced on the PacBio RSII and Illumina MiSeq sequencers. Phylogenetic classification positioned the strain ING2-E5AT in close proximity to Fermentimonas and Proteiniphilum species (family Dysgonomonadaceae). ING2-E5AT encodes a number of genes for glycosyl-hydrolyses (GH) which are organized in Polysaccharide Utilization Loci (PUL) comprising tandem susCD-like genes for a TonB-dependent outer-membrane transporter and a cell surface glycan-binding protein. Different GHs encoded in PUL are involved in pectin degradation, reflecting a pronounced specialization of the ING2-E5AT PUL systems regarding the decomposition of this polysaccharide. Genes encoding enzymes participating in amino acids fermentation were also identified. Fragment recruitments with the ING2-E5AT genome as a template and publicly available metagenomes of AD microbiomes revealed that Petrimonas species are present in 146 out of 257 datasets supporting their importance in AD microbiomes. Metatranscriptome analyses of AD microbiomes uncovered active sugar and amino acid fermentation pathways for Petrimonas species. Likewise, screening of metaproteome datasets demonstrated expression of the Petrimonas PUL-specific component SusC providing further evidence that PUL play a central role for the lifestyle of Petrimonas species.

Biogas Potential of Wastes and By-Products of the Alcoholic Beverage Production Industries in the Spanish Region of Cantabria

The industry of alcoholic beverage production has been, historically, both an important economic engine and a source of wastes and pollution (due to the production processes by themselves and to the energy requirements) in a number of countries. In the small region of Cantabria, in northern Spain, the production of alcoholic beverages as an economic sector has been growing in importance in recent years. Thus, there is a new flow of waste for which specific management plans have yet to be developed. The result is an increase in the total amount of urban waste to be disposed. Anaerobic digestion can be a suitable in-situ solution for the treatment of the generated wastes providing a source of renewable energy which can be a supply for the processes in these industries, reducing the emission of greenhouse gases associated to the use of fossil fuels, all of this benefitting both environment and economy. In this work the authors present the information gathered about waste generation and the biomethanogenic potential of the most important wastes generated in the industries. As a result, specific strategies could be designed for the industrial sector in the region, of which other small agro-industries can benefit.

Biogenic Fe(II-III) Hydroxycarbonate Green Rust Enhances Nitrate Removal and Decreases Ammonium Selectivity during Heterotrophic Denitrification

Nitrification-denitrification is the most widely used nitrogen removal process in wastewater treatment. However, this process can lead to undesirable nitrite accumulation and subsequent ammonium production. Biogenic Fe(II-III) hydroxycarbonate green rust has recently emerged as a candidate to reduce nitrite without ammonium production under abiotic conditions. The present study investigated whether biogenic iron(II-III) hydroxycarbonate green rust could also reduce nitrite to gaseous nitrogen during bacterial nitrate reduction. Our results showed that biogenic iron(II-III) hydroxycarbonate green rust could efficiently decrease the selectivity of the reaction towards ammonium during heterotrophic nitrate reduction by native wastewater-denitrifying bacteria and by three different species of Shewanella: S. putrefaciens ATCC 12099, S. putrefaciens ATCC 8071 and S. oneidensis MR-1. Indeed, in the absence of biogenic hydroxycarbonate green rust, bacterial reduction of nitrate converted 11–42% of the initial nitrate into ammonium, but this value dropped to 1–28% in the presence of biogenic hydroxycarbonate green rust. Additionally, nitrite accumulation did not exceed the 2–13% in the presence of biogenic hydroxycarbonate green rust, versus 0–28% in its absence. Based on those results that enhance the extent of denitrification of about 60%, the study proposes a water treatment process that couples the bacterial nitrite production with the abiotic nitrite reduction by biogenic green rust.

Sugar-alcohol industry: quality of its biotreated washing water for reuse in fertigation

All processes in agro-industries consume water and generate large volumes of nutrient-rich effluents. To recycle effluents from a sugar-alcohol industry in the Northeastern Brazil (Coruripe, Alagoas), the effect of a daily application of a microbial formulation (containing five indigenous bacteria and two fungi), at the entrance of the two first facultative ponds (D, E) of its treatment plant formed by seven ponds (A-G), was evaluated in the sugarcane harvests of 2014/2015 and 2015/2016. Fortnightly, the values of 11 physicochemical parameters were checked and statistically compared (one and two-way ANOVA) in untreated (sedimentation pond A) and post-treated effluent (last facultative pond G), during both harvests. The treated effluent presented statistically significant improvements (p > 0.05), even between harvests, with averages of removal of organic matter of ca. 79.21% and 90.62%, and increases of the dissolved oxygen (DO) of ca. 72% and 74%, as well as the average increase of pH was ca. 42% and 50%. This better quality residue generally satisfied the class III level of the Brazilian Resolution 357/2005 (National Council for the Environment (CONAMA)), for water reuse in sugarcane irrigation on the yellow clay latosol soil, since it still is a light source of organic matter, nitrites and phosphorus, reducing the need of fertilizers for maintaining the productivity with low risk of salinization. According to Pearson's bivariate correlation coefficient, while the DO and pH have positive correlation, they both have general inverse relation with the other physicochemical parameters evaluated and vice versa.

Enhanced Biogas Production of Cassava Wastewater Using Zeolite and Biochar Additives and Manure Co-Digestion

Currently, there are challenges with proper disposal of cassava processing wastewater, and a need for sustainable energy in the cassava industry. This study investigated the impact of co-digestion of cassava wastewater (CW) with livestock manure (poultry litter (PL) and dairy manure (DM)), and porous adsorbents (biochar (B-Char) and zeolite (ZEO)) on energy production and treatment efficiency. Batch anaerobic digestion experiments were conducted, with 16 treatments of CW combined with manure and/or porous adsorbents using triplicate reactors for 48 days. The results showed that CW combined with ZEO (3 g/g total solids (TS)) produced the highest cumulative CH4 (653 mL CH4/g VS), while CW:PL (1:1) produced the most CH4 on a mass basis (17.9 mL CH4/g substrate). The largest reduction in lag phase was observed in the mixture containing CW (1:1), PL (1:1), and B-Char (3 g/g TS), yielding 400 mL CH4/g volatile solids (VS) after 15 days of digestion, which was 84.8% of the total cumulative CH4 from the 48-day trial. Co-digesting CW with ZEO, B-Char, or PL provided the necessary buffer needed for digestion of CW, which improved the process stability and resulted in a significant reduction in chemical oxygen demand (COD). Co-digestion could provide a sustainable strategy for treating and valorizing CW. Scale-up calculations showed that a CW input of 1000–2000 L/d co-digested with PL (1:1) could produce 9403 m3 CH4/yr using a 50 m3 digester, equivalent to 373,327 MJ/yr or 24.9 tons of firewood/year. This system would have a profit of $5642/yr and a $47,805 net present value.

Evaluation and Predictive Modeling of Removal Condition for Bioadsorption of Indigo Blue Dye by Spirulina platensis

Among the different chemical and physical treatments used to remove the color of the textile effluents, bioremediation offers many benefits to the environment. In this study, we determined the potential of Spirulina platensis (S. platensis) for decolorizing indigo blue dye under different incubation conditions. The microalgae were incubated at different pH (from 4 to 10) to calibrate for the optimal discoloration condition; a pH of 4 was found to be optimal. The biomass concentration in all experiments was 1 g/L, which was able to decolorize the indigo blue dye by day 3. These results showed that S. platensis is capable of removing indigo blue dye at low biomass. However, this was dependent on the treatment conditions, where temperature played the most crucial role. Two theoretical adsorption models, namely (1) a first-order model equation and (2) a second-order rate equation, were compared with observed adsorption vs. time curves for different initial concentrations (from 25 to 100 mg/L). The comparison between models showed similar accuracy and agreement with the experimental values. The observed adsorption isotherms for three temperatures (30, 40, and 50 °C) were plotted, showing fairly linear behavior in the measured range. The adsorption equilibrium isotherms were estimated, providing an initial description of the dye removal capacity of S. platensis.

Modelling biofilm anaerobic reactor with effluent from hydrolytic/acidogenic reactor as substrate

This work presents modelling of an anaerobic biofilm reactor using ceramic bricks as support. The results were compared with the experimental data. It was observed that the substrate concentration curves showed the same tendency. The methane formation curves showed significant differences. The substrate removal efficiency was 83%. In the steady state, the experimental data were higher than the model, from the result the substrate degrading bacteria grew enough to reach biofilm and that the effect of the shear stress was more significant as the biofilm increased in thickness. To the methane production, the model in steady state reached a maximum value of 0.56 m³ CH₄/m³ *d and the experimental data reached 0.42 (m³ CH₄/m³ * d). The biofilm thickness calculated by the model was 14 μm.

Development of Anaerobic High-Rate Reactors, Focusing on Sludge Bed Technology

In the last 40 years, anaerobic sludge bed reactor technology has evolved from localized laboratory-scale trials to worldwide successful implementations in a variety of industries. High-rate sludge bed reactors are characterized by a very small footprint and high applicable volumetric loading rates. Best performances are obtained when the sludge bed consists of highly active and well settleable granular sludge. Sludge granulation provides a rich microbial diversity, high biomass concentration, high solids retention time, good settling characteristics, reduction in both operation costs and reactor volume, and high tolerance to inhibitors and temperature changes. However, sludge granulation cannot be guaranteed on every type of industrial wastewater. Especially in the last two decades, various types of high-rate anaerobic reactor configurations have been developed that are less dependent on the presence of granular sludge, and many of them are currently successfully used for the treatment of various kinds of industrial wastewaters worldwide. This study discusses the evolution of anaerobic sludge bed technology for the treatment of industrial wastewaters in the last four decades, focusing on granular sludge bed systems.

Biogas Production: Microbiology and Technology

Biogas, containing energy-rich methane, is produced by microbial decomposition of organic material under anaerobic conditions. Under controlled conditions, this process can be used for the production of energy and a nutrient-rich residue suitable for use as a fertilising agent. The biogas can be used for production of heat, electricity or vehicle fuel. Different substrates can be used in the process and, depending on substrate character, various reactor technologies are available. The microbiological process leading to methane production is complex and involves many different types of microorganisms, often operating in close relationships because of the limited amount of energy available for growth. The microbial community structure is shaped by the incoming material, but also by operating parameters such as process temperature. Factors leading to an imbalance in the microbial community can result in process instability or even complete process failure. To ensure stable operation, different key parameters, such as levels of degradation intermediates and gas quality, are often monitored. Despite the fact that the anaerobic digestion process has long been used for industrial production of biogas, many questions need still to be resolved to achieve optimal management and gas yields and to exploit the great energy and nutrient potential available in waste material. This chapter discusses the different aspects that need to be taken into consideration to achieve optimal degradation and gas production, with particular focus on operation management and microbiology.