Trends and resource recovery in biological wastewater treatment system

Nanomaterials - A promising solution for textile and fossil fuel generated pollutants

This review approach is divided into two scopes to focus the pollution threats. We cover the applications of nanomaterials to curtail the pollution induced by fossil fuel combustion, and textile dye effluents. Toxic emissions released from automobile exhaust that comprise of NOX. SOX and PAHs compile to harsh breathing and respiratory troubles. The effluents generated from the mammoth textile and leather industry is potential threat to beget massive health issues to human life, and environmental problem. Part I projects the broad envisage on role of nano materials in production of alternative biofuels. In addition, green sources for synthesizing nanomaterials are given special importance. Nano catalyst's utilization in bio-derived fuels such as biogas, bio-oil, bioethanol, and biodiesel are catered to this article. Part II cover the current statistics of textile effluent pollution level in India and its steps in confronting the risks of pollution are discussed. A clear picture of the nano techniques in pre-treatment, and the recent nano related trends pursued in industries to eliminate the dyes and chemicals from the discharges is discussed. The substantial aspect of nano catalysis in achieving emission-free fuel and toxic-free effluents and the augmentation in this field is conferred. This review portrays the dependency on nano materials & technology for sustainable future.

Model-based fractionation of biomass in a biological nutrient removal system and its effect on the removal efficiencies

Fractionation of active biomass in a five-stage Bardenpho process was accomplished using an MS Excel wastewater treatment plant modeling tool based on Activated Sludge Model No. 3 extended with a bio-P module. The biomass fractions within the treatment system were predicted as autotrophs, ordinary heterotrophs, and phosphorus accumulating organisms (PAOs). Several simulations were performed in a Bardenpho process using various C/N/P ratios in primary effluent. Biomass fractionation was obtained from steady-state simulation results. The results suggest that the mass percentage of autotrophs, heterotrophs, and PAOs in active biomass range from 1.7 to 7.8%, 5.7-69.0%, and 23.2-92.6%, respectively, depending on characteristics of primary effluent. Results of principal component analysis showed that TKN/COD ratio in primary effluent determines the population of autotrophs and ordinary heterotrophs whereas PAO population is mainly a function of TP/COD ratio.

Enhanced bioenergy and nutrients recovery from wastewater using hybrid anodes in microbial nutrient recovery system

Background

The combined microbial fuel cell–microbial nutrient recovery system has lately been thoroughly explored from an engineering standpoint. The relevance of microbial communities in this process, on the other hand, has been widely underestimated.

Results

A lab-scale microbial nutrients recovery system was created in this work, and the microbial community structure was further defined, to give a thorough insight into the important microbial groups in the present system. We reported for the first-time different hybrid anodes of activated carbon and chitosan that were used in the microbial nutrient recovery system for bioenergy production, and, for the removal of COD and recovery of nutrients present in the wastewater. The hybrid anodic materials were studied to adapt electrochemically active bacteria for the recovery of nutrients and energy generation from wastewater without the need for an external source of electricity. The potential of the created hybrid anodes in terms of nutrients recovery, chemical oxygen demand elimination, and energy generation from municipal wastewater was thoroughly examined and compared with each other under similar operating conditions. When the COD loading was 718 mg/L, a total COD removal of ~ 79.2% was achieved with a hybrid activated carbon and chitosan anode having an equal ratio after 10 days of the operation cycle. The maximum power density estimated for hybrid anode (~ 870 mWm⁻²) was found.

Conclusion

Overall, this work reveals a schematic self-driven way for the collection and enrichment of nutrients (~ 72.9% phosphorus recovery and ~ 73% ammonium recovery) from municipal wastewater, as well as consistent voltage production throughout the operation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13068-022-02116-y.

Prospects and trends in bioelectrochemical systems: Transitioning from CO2 towards a low-carbon circular bioeconomy

Resource scarcity and climate change are the most quested topics in view of environmental sustainability. CO2 sequestration through bioelectrochemical systems is an attractive option for fostering bioeconomy development upon several value-added products generation. This review details the state-of-the-art of bioelectrochemical systems for resource recovery from CO2 along with various biocatalysts capable of utilizing CO2. Two bioprocesses (photo-electrosynthesis and chemolithoelectrosynthesis) were discussed projecting their potential for biobased economy development from CO2. Significance of adopting circular strategies for efficient resource recycling, intensifying product value, integrations/interlinking of multiple process chains for the development of circular bioeconomy were discussed. Existing constrains as well as outlook for near establishment of circular bioeconomy from CO2 is presented by weighing fore-sighted plans with current actions. Need for developing CO2-based circular bioeconomy via innovative business models by analyzing social, technical, environmental and product related aspects are also discussed providing a roadmap of gaps to pursue for attaining practicality.

Situation Analysis and the Potential for Circularity of the Wastewater Sector in Lithuania

The concept of circular economy is one of the priority areas for economic development on which the current environmental policy of the European Union is based. Most existing European wastewater treatment plants were built and operated according to the concept of linear economy where wastewater and sewage sludge were considered as waste only. In fact, there is a wide range of possibilities to use them as a resource to recover materials and energy. Implementation of the concept of circular economy in a relatively small country requires a great deal of additional research and monitoring to assess the available potential. In this paper, data on municipal wastewater in agglomerations larger than population equivalent of 2000 were analyzed, and the situation is presented through indicators covering prevention, removal, reuse, recycling, and recovery. The novelty of this article is that it evaluates the circularity of Lithuanian wastewater treatment plants and their potential for the future. Thus far, the wastewater sector in the country has been found to largely comply with legal obligations, but very few solutions of circularity were found to be implemented.

Renewable Energy-Driven Desalination: New Trends and Future Prospects of Small Capacity Systems

New trends and future prospects for small capacity systems of Renewable Energy-driven DESalination (REDES) are reviewed and assessed in this paper over a nominal desalination capacity range of 3–1000 m3/d. A thorough literature review is reported in order to evaluate current research and developing activities. Outstanding commercial prospects in the near future are identified for two off-grid REDES technologies under development. First, wave energy converters with direct coupling to seawater desalination. Second, solar micro gas turbines with biofuel backup coupled to reverse osmosis (RO) desalination and/or zero liquid discharge water treatment. These systems, as well as mature REDES plants (namely PV/RO and wind turbines/RO), will benefit from forthcoming advances in energy efficiency in the RO process itself. The Closed Circuit RO desalination (CCROTM) concept may be a key configuration for enhancing RE-driven RO desalination. Additionally, opportunities for innovation in seawater RO desalination with variable power consumption are highlighted. On the other hand, our conclusions highlight opportunities for developing novel portable REDES systems based on solar membrane distillation with a portable linear Fresnel concentrator manufactured by SOLATOM. Additionally, the concept of portable systems could foster the commercial development of microbial desalination cells combined with solar PV energy and RO powered by tidal currents.

Could termites be hiding a goldmine of obscure yet promising yeasts for energy crisis solutions based on aromatic wastes? A critical state-of-the-art review

Biodiesel is a renewable fuel that can be produced from a range of organic and renewable feedstock including fresh or vegetable oils, animal fats, and oilseed plants. In recent years, the lignin-based aromatic wastes, such as various aromatic waste polymers from agriculture, or organic dye wastewater from textile industry, have attracted much attention in academia, which can be uniquely selected as a potential renewable feedstock for biodiesel product converted by yeast cell factory technology. This current investigation indicated that the highest percentage of lipid accumulation can be achieved as high as 47.25% by an oleaginous yeast strain, Meyerozyma caribbica SSA1654, isolated from a wood-feeding termite gut system, where its synthetic oil conversion ability can reach up to 0.08 (g/l/h) and the fatty acid composition in yeast cells represents over 95% of total fatty acids that are similar to that of vegetable oils. Clearly, the use of oleaginous yeasts, isolated from wood-feeding termites, for synthesizing lipids from aromatics is a clean, efficient, and competitive path to achieve "a sustainable development" towards biodiesel production. However, the lacking of potent oleaginous yeasts to transform lipids from various aromatics, and an unknown metabolic regulation mechanism presented in the natural oleaginous yeast cells are the fundamental challenge we have to face for a potential cell factory development. Under this scope, this review has proposed a novel concept and approach strategy in utilization of oleaginous yeasts as the cell factory to convert aromatic wastes to lipids as the substrate for biodiesel transformation. Therefore, screening robust oleaginous yeast strain(s) from wood-feeding termite gut system with a set of the desirable specific tolerance characteristics is essential. In addition, to reconstruct a desirable metabolic pathway/network to maximize the lipid transformation and accumulation rate from the aromatic wastes with the applications of various "omics" technologies or a synthetic biology approach, where the work agenda will also include to analyze the genome characteristics, to develop a new base mutation gene editing technology, as well as to clarify the influence of the insertion position of aromatic compounds and other biosynthetic pathways in the industrial chassis genome on the expressional level and genome stability. With these unique designs running with a set of the advanced biotech approaches, a novel metabolic pathway using robust oleaginous yeast developed as a cell factory concept can be potentially constructed, integrated and optimized, suggesting that the hypothesis we proposed in utilizing aromatic wastes as a feedstock towards biodiesel product is technically promising and potentially applicable in the near future.

Indicators for resource recovery monitoring within the circular economy model implementation in the wastewater sector

The European Union is currently in the process of transformation toward a circular economy model in which different areas of activity should be integrated for more efficient management of raw materials and waste. The wastewater sector has a great potential in this regard and therefore is an important element of the transformation process to the circular economy model. The targets of the circular economy policy framework such as resource recovery are tightly connected with the wastewater treatment processes and sewage sludge management. With this in view, the present study aims to review existing indicators on resource recovery that can enable efficient monitoring of the sustainable and circular solutions implemented in the wastewater sector. Within the reviewed indicators, most of them were focused on technological aspects of resource recovery processes such as nutrient removal efficiency, sewage sludge processing methods and environmental aspects as the pollutant share in the sewage sludge or its ashes. Moreover, other wide-scope indicators such as the wastewater service coverage or the production of bio-based fertilizers and hydrochar within the wastewater sector were analyzed. The results were used for the development of recommendations for improving the resources recovery monitoring framework in the wastewater sector and a proposal of a circularity indicator for a wastewater treatment plant highlighting new challenges for further researches and wastewater professionals.

Biofilm with highly heterogeneous interior structure for pollutant removal: Cell distribution and manipulated mass transport

Biofilm wastewater treatment had been applied in practice. Conventionally the biofilm was modeled as a uniform structure to simplify the analysis. This study for the first time established a three-dimensional biofilm model with distributions separating living cells, Extracellular polymeric substances (EPS) and pores, based on which the local fluid flow velocity and pollutant diffusion and reaction fluxes inside the biofilm were numerically evaluated. Both the uniform structured and previously proposed heterogeneous models had been confirmed to overestimate the performances of a biofilm for wastewater treatment. The survival strategies of living cells in biofilm were discussed. Besides exposing to fresh pollutants for maximizing pollutant uptake, the tendency to form small aggregates of cells for shortening diffusion length so furnishing the pollutant with reduced diffusional resistance to living cells was also for the first time noted. This communication advanced the knowledge to comprehend the detailed processes in biofilm.

Bioprocesses for the recovery of bioenergy and value-added products from wastewater: A review

Wastewater and activated sludge present a major challenge worldwide. Wastewater generated from large and small-scale industries, laundries, human residential areas and other sources is emerging as a main problem in sanitation and maintenance of smart/green cities. During the last decade, different technologies and processes have been developed to recycle and purify the wastewater. Currently, identification and fundamental consideration of development of more advanced microbial-based technologies that enable wastewater treatment and simultaneous resource recovery to produce bioenergy, biofuels and other value-added compounds (organic acids, fatty acids, bioplastics, bio-pesticides, bio-surfactants and bio-flocculants etc.) became an emerging topic. In the last several decades, significant development of bioprocesses and techniques for the extraction and recovery of mentioned valuable molecules and compounds from wastewater, waste biomass or sludge has been made. This review presents different microbial-based process routes related to resource recovery and wastewater application for the production of value-added products and bioenergy. Current process limitations and insights for future research to promote more efficient and sustainable routes for this under-utilized and continually growing waste stream are also discussed.

Recent Progress and Challenges in Hollow Fiber Membranes for Wastewater Treatment and Resource Recovery

Membrane processes have been extensively employed in diverse applications, specifically in industrial wastewater treatment. The technological development in membrane processes has rapidly advanced and accelerated beyond its common principle and operation. Tremendous efforts have been made in the advancement of membrane materials, fabrication method, membrane modification and integration with other technologies that can augment the existing membrane processes to another level. This review presents the recent development of hollow fiber membranes applied in wastewater treatment and resource recovery. The membrane working principles and treatment mechanism were discussed thoroughly, with the recent development of these hollow fiber membranes highlighted based on several types of membrane application. The current challenges and limitations which may hinder this technology from expanding were critically described to offer a better perspective for this technology to be adopted in various potential applications.

Investigation of critical sludge characteristics for membrane fouling in a submerged membrane bioreactor: Role of soluble microbial products and extracted extracellular polymeric substances

Membrane bioreactors (MBRs) are considered a promising tool for resource recovery in wastewater treatment. Nevertheless, membrane fouling is an inevitable phenomenon that deteriorates the MBR performance. Although many studies have attempted to elucidate the effect of sludge characteristics on MBR fouling, they posed certain limitations. Most of the previous studies focused on the initial sludge or employ the results of short-term batch tests without long-term transmembrane pressure (TMP) profiles in the interpretation of fouling behaviors. This study was conducted considering these limitations to determine the sludge characteristics most closely related to long-term TMP profiles and to identify their role in fouling behaviors. In long-term TMP profiles, critical time (t_c; time to TMP jump) and fouling rates (the increase in the TMP slope) were used as fouling indexes, which were used to correlate with average values of sludge characteristics before and after experiments. According to the results, the concentration of the total soluble microbial product (SMP) and extracted extracellular polymeric substance (eEPS) in sludge significantly increased by 1.9 times and up to 28 times after experiment. The increase in the SMP and eEPS caused early TMP jumps and resulted in low-fouling rates by increasing particle size. Owing to the increase in the SMP and eEPS concentration, the origin of fouling potential was shifted from suspended solids to colloids and soluble materials. Fouling resistance caused by soluble material increased by up to 11.38 times.

Economic evaluation of the reuse of brewery wastewater

Freshwater scarcity is a global concern, not just in countries with limited water resources, and wastewater reuse is becoming an essential necessity. Beer is the fifth-most widely consumed beverage in the world and breweries are a major industrial water consumer. Within this study, the long-term performance of a modular pilot scale plant reusing brewery wastewater was investigated. The system consisted of a flotation device, a membrane bioreactor (MBR), an ultrafiltration (UF) and a reverse osmosis (RO) system. The system was fed with wastewater from the effluent of a full-scale anaerobic reactor. The combination of flotation device and MBR removed chemical oxygen demand (COD) by 93.6%. The subsequent UF and RO removed remaining organic load and inorganic components and process water was produced, whereby drinking water quality was achieved. A yield of 63% was reached with the pilot plant. Based on the results, a base case cost estimate was carried out for a full-scale application, taking into account the actual hydraulic load of the brewery. In order to predict the uncertainties of cost-sensitive factors, the specific costs for sludge disposal, electrical energy, freshwater supply and wastewater disposal as well as membrane lifespan and yield of the RO unit were expressed by probability distributions. Using the Monte Carlo method with 75,000 iterations, the probability distributions for the costs and economic viability of reusing brewery wastewater were calculated. The estimate found that reusing brewery wastewater can be economically viable in 77.2% of simulated cases showing the strongest dependency on costs for wastewater disposal.

Performance of Pistia stratiotes, Salvinia molesta, and Eichhornia crassipes Aquatic Plants in the Tertiary Treatment of Domestic Wastewater with Varying Retention Times

Organic matter, nutrients, and chemicals are some of the waste materials found in most domestic wastewaters. The purpose of this research was to evaluate the potentials of Pistia stratiotes, Salvinia molesta, and Eichhornia crassipes aquatic weed plants in the tertiary treatment of secondary domestic wastewater using hydroponic systems. Physicochemical analysis that considered turbidity, phosphate, ammoniacal nitrogen, and nitrate was conducted on the wastewater samples at different retention times of 6, 12, and 24 h for 14 days. The best performance was observed for a 24 h retention treatment system, with up to 91% (P. stratiotes), 94% (S. molesta), and 89.3% (E. crassipes) reduction for turbidity; 81.2% (P. stratiotes), 82.7% (S. molesta), and 88.5% (E. crassipes) for phosphate reduction; 88.66% (P. stratiotes), 90.47% (S. molesta), and 89.11% (E. crassipes) for ammoniacal nitrogen reduction; 83.6% (P. stratiotes), 92.1% (S. molesta) and 93% (E. crassipes) for nitrate reduction. Hence, the application of hydroponic systems in cultivation of the macrophytes proved to be effective in the phytoremediation process by removing the residual nutrients present in the treated secondary domestic wastewater. Additionally, this method can be used for the cultivation of plant-based biomass and other non-edible useful crops using the free nutrients content of the wastewater before its discharge into the natural environment.

Glucose fermentation with biochar-amended consortium: microbial consortium shift

The effects of adding biochar rice husk (R), white popinee (WP), bamboo (BB), or coconut (CT) on microbial community in fermentation broths from glucose were investigated. The added biochars acted as biofilm carriers on which Sporolactobacillus spathodeae, Clostridium sensu stricto 11 sp., Clostridium sensu stricto 12 sp., Clostridium sensu stricto 1 sp., and Clostridium sensu stricto 5 sp. were enriched. Fermentation reactions substantially increased the amounts of acid-producers in biofilm. The homoacetogens, Clostridium carboxidivorans and Clostridium drakei, were identified in the biofilm in the first two batches of fermentation with biochars as electron conductors between acid-producers and homoacetogens to assist homoacetogenesis. The heterotrophic bacteria overcompeted the acid-producers in the biofilm in long-term fermentation.

Life Cycle Assessment of the Mesophilic, Thermophilic, and Temperature-Phased Anaerobic Digestion of Sewage Sludge

In this study the environmental impact of the anaerobic digestion (AD) of sewage sludge within an activated sludge wastewater treatment plant (WWTP) was investigated. Three alternative AD systems (mesophilic, thermophilic, and temperature-phased anaerobic digestion (TPAD)) were compared to determine which system may have the best environmental performance. Two life cycle assessments (LCA) were performed considering: (i) the whole WWTP (for a functional unit (FU) of 1 m3 of treated wastewater), and (ii) the sludge line (SL) alone (for FU of 1 m3 of produced methane). The data for the LCA were obtained from previous laboratory experimental work in combination with full-scale WWTP and literature. According to the results, the WWTP with TPAD outperforms those with mesophilic and thermophilic AD in most analyzed impact categories (i.e., Human toxicity, Ionizing radiation, Metal and Fossil depletion, Agricultural land occupation, Terrestrial acidification, Freshwater eutrophication, and Ozone depletion), except for Climate change where the WWTP with mesophilic AD performed better than with TPAD by 7%. In the case of the SL alone, the production of heat and electricity (here accounted for as avoided environmental impacts) led to credits in most of the analyzed impact categories except for Human toxicity where credits did not balance out the impacts caused by the wastewater treatment system. The best AD alternative was thermophilic concerning all environmental impact categories, besides Climate change and Human toxicity. Differences between both LCA results may be attributed to the FU.

Towards the Implementation of Circular Economy in the Wastewater Sector: Challenges and Opportunities

The advancement of science has facilitated increase in the human lifespan, reflected in economic and population growth, which unfortunately leads to increased exploitation of resources. This situation entails not only depletion of resources, but also increases environmental pollution, mainly due to atmospheric emissions, wastewater effluents, and solid wastes. In this scenario, it is compulsory to adopt a paradigm change, as far as the consumption of resources by the population is concerned, to achieve a circular economy. The recovery and reuse of resources are key points, leading to a decrease in the consumption of raw materials, waste reduction, and improvement of energy efficiency. This is the reason why the concept of the circular economy can be applied in any industrial activity, including the wastewater treatment sector. With this in view, this review manuscript focuses on demonstrating the challenges and opportunities in applying a circular economy in the water sector. For example, reclamation and reuse of wastewater to increase water resources, by paying particular attention to the risks for human health, recovery of nutrients, or highly added-value products (e.g., metals and biomolecules among others), valorisation of sewage sludge, and/or recovery of energy. Being aware of this situation, in the European, Union 18 out of 27 countries are already reusing reclaimed wastewater at some level. Moreover, many wastewater treatment plants have reached energy self-sufficiency, producing up to 150% of their energy requirements. Unfortunately, many of the opportunities presented in this work are far from becoming a reality. Still, the first step is always to become aware of the problem and work on optimizing the solution to make it possible.