Biological Wastewater Treatment Technology Research Articles

Salt stimulates sulfide−driven autotrophic denitrification: Microbial network and metagenomics analyses

Sulfur autotrophic denitrification (SADN) is a promising biological wastewater treatment technology for nitrogen removal, and its performance highly relies on the collective activities of the microbial community. However, the effect of salt (a prevailing characteristic of some nitrogen−containing industrial wastewaters) on the microbial community of SADN is still unclear. In this study, the response of the sulfide−SADN process to different salinities (i.e., 1.5 % salinity, 0.5 % salinity, and without salinity) as well as the involved microbial mechanisms were investigated by molecular ecological network and metagenomics analyses. Results showed that the satisfactory nitrogen removal efficiency (>97 %) was achieved in the sulfide−SADN process (S/N molar ratio of 0.88) with 1.5 % salinity. In salinity scenarios, the genus Thiobacillus significantly proliferated and was detected as the dominant sulfur−oxidizing bacteria in the sulfide−SADN system, occupying a relative abundance of 29.4 %. Network analysis further elucidated that 1.5 % salinity had enabled the microbial community to form a more densely clustered network, which intensified the interactions between microorganisms and effectively improved the nitrogen removal performance of the sulfide−SADN. Metagenomics sequencing revealed that the abundance of functional genes encoding for key enzymes involved in SADN, dissimilatory nitrate reduction to ammonium, and nitrification was up−regulated in the 1.5 % salinity scenario compared to that without salinity, stimulating the occurrence of multiple nitrogen transformation pathways. These multi−paths contributed to a robust SADN process (i.e., nitrogen removal efficiency >97 %, effluent nitrogen <2.5 mg N/L). This study deepens our understanding of the effect of salt on the SADN system at the community and functional level, and favors to advance the application of this sustainable bioprocess in saline wastewater treatment.

Microbial Ecology of Granular Biofilm Technologies for Wastewater Treatment: A Review.

Nowadays, the discharge of wastewater is a global concern due to the damage caused to human and environmental health. Wastewater treatment has progressed to provide environmentally and economically sustainable technologies. The biological treatment of wastewater is one of the fundamental bases of this field, and the employment of new technologies based on granular biofilm systems is demonstrating success in tackling the environmental issues derived from the discharge of wastewater. The granular-conforming microorganisms must be evaluated as functional entities because their activities and functions for removing pollutants are interconnected with the surrounding microbiota. The deep knowledge of microbial communities allows for the improvement in system operation, as the proliferation of microorganisms in charge of metabolic roles could be modified by adjustments to operational conditions. This is why engineering must consider the intrinsic microbiological aspects of biological wastewater treatment systems to obtain the most effective performance. This review provides an extensive view of the microbial ecology of biological wastewater treatment technologies based on granular biofilms for mitigating water pollution.

A novel method for identifying aerobic granular sludge state using sorting, densification and clarification dynamics during the settling process

Aerobic granular sludge is one of the most promising biological wastewater treatment technologies, yet maintaining its stability is still a challenge for its application, and predicting the state of the granules is essential in addressing this issue. This study explored the potential of dynamic texture entropy, derived from settling images, as a predictive tool for the state of granular sludge. Three processes, traditional thickening, often overlooked clarification, and innovative particle sorting, were used to capture the complexity and diversity of granules. It was found that rapid sorting during settling indicates stable granules, which helps to identify the state of granules. Furthermore, a relationship between sorting time and granule heterogeneity was identified, helping to adjust selection pressure. Features of the dynamic texture entropy well correlated with the respirogram, i.e., R2 were 0.86 and 0.91 for the specific endogenous respiration rate (SOURe) and the specific quasi-endogenous respiration rate (SOURq), respectively, providing a biologically based approach for monitoring the state of granules. The classification accuracy of models using features of dynamic texture entropy as an input was greater than 0.90, significantly higher than the input of conventional features, demonstrating the significant advantage of this approach. These findings contributed to developing robust monitoring tools that facilitate the maintenance of stable granular sludge operations.

A systemic evaluation of aerobic granular sludge among granulation, operation, storage, and reactivation processes in an SBR

As a biological promising wastewater treatment technology, aerobic granular sludge (AGS) technology had been widely studied in sequencing batch reactors (SBRs) for the decades. Presently, the whole processes of its granulation, long-term operation, storage, and reactivation have not been thoroughly evaluated, and also the relationships among microbial diversity, granular size, and characteristics were still not that clear. Hence, they were systematically evaluated in an AGS-SBR in this work. The results demonstrated that Proteobacteria and Bacteroidetes were the dominant phyla, Flavobacterium, Acinetobacter, Azoarcus, and Chryseobacterium were the core genera with discrepant abundances in diverse stages or granular size. Microbial immigration was significant in various stages due to microbial diversity had a line relationship with COD/MLVSS ratio (R2 = 0.367). However, microbial diversity had no line relationship with granular size (R2 = 0.001), indicating the microbial diversity in different-sized AGS was similar, although granular size had a line relationship with settleability (R2 = 0.978). Overall, compared to sludge traits (e.g., sludge size, settleability), COD/MLVSS played a key role on microbial evolution. This study revealed the relationships between granule characteristics and microbial community, and contributed to the future AGS-related studies.

The iron cycling mediated by a single strain Shewanella oneidensis MR-1 and its implication for nitrogen removal

Microbially mediated nitrate-reducing Fe(II) oxidation (NRFO) process has been recognized as an effective route for removing nitrogen in wastewater. However, the need for continuous dose of iron blocks NRFO technology to be scaled up. Microbial iron cycling can improve iron utilization efficiency, but whether it can be mediated by a single strain remains elusive. Here, Shewanella oneidensis strain MR-1 was employed to mediate Fe redox process with the subsequent addition of Fe(III), nitrate, and lactate under anaerobic conditions. Fe(II) kinetic curve showed that strain MR-1 could efficiently reduce Fe(III) with a reduction rate of 2.55 mmol·L−1·d−1, producing a great amount of Fe(II). After nitrate addition, strain MR-1 mediated the NRFO process. Fe(III) reduction and NRFO constituted Fe cycle, indicating that strain MR-1 successfully carried out Fe redox cycling. It is noted that two iron redox cycles were achieved, but the second cycle was weaker. That is, about 86.7 % of total iron was reduced in the first cycle, but only 4.6 % was reduced in the second cycle. As nitrate reduction is the key process for iron cycling, the unsustainability should be related to nitrate reduction inhibition. The possible mechanisms were investigated, revealing that nitrate reduction was inhibited by cell encrustation and nutrient shortage. These findings expand the understanding of microbial iron cycle and provide a new microbial iron cycling model. This will help to improve the biological wastewater treatment technology based on NRFO process.

A Review of Rotating Biological Contactors for Wastewater Treatment

A rotating biological contactor (RBC) is a type of attached-growth biological wastewater treatment system and a widely used biological wastewater treatment technology. It employs a series of rotating discs to support microbial growth and promote the removal of pollutants from wastewater. RBC is widely recognized for its simplicity of design, high reliability, and low energy consumption. It has been used in various applications, from small-scale decentralized systems to large municipal wastewater treatment plants. The current review provides an overview of RBC bioreactors, design parameters, and the factors that influence biological performance, such as hydraulic retention time, sludge retention time, organic loading rate, disc rotational speed, and temperature. The review also highlights the advantages and disadvantages of RBCs compared with other wastewater treatment technologies and discusses their role in sustainable environmental performance. The future prospects of RBC are also discussed, including integration with other technologies, such as membrane filtration and potential use in resource recovery. The review explores the application of RBC in decentralized wastewater treatment and the potential to provide sustainable solutions for wastewater management in rural and remote areas. Overall, RBC remains a promising option for effective and efficient wastewater treatment, particularly in situations where simplicity, reliability, and low energy consumption are desired.

Immobilized microalgal system: An achievable idea for upgrading current microalgal wastewater treatment.

Efficient wastewater treatment accompanied by sustainable "nutrients/pollutants waste-wastewater-resources/energy nexus" management is acting as a prominent and urgent global issue since severe pollution has occurred increasingly. Diverting wastes from wastewater into the value-added microalgal-biomass stream is a promising goal using biological wastewater treatment technologies. This review proposed an idea of upgrading the current microalgal wastewater treatment by using immobilized microalgal system. Firstly, a systematic analysis of microalgal immobilization technology is displayed through an in-depth discussion on why using immobilized microalgae for wastewater treatment. Subsequently, the main technical approaches employed for microalgal immobilization and pollutant removal mechanisms by immobilized microalgae are summarized. Furthermore, from high-tech technologies to promote large-scale production and application potentials in diverse wastewater and bioreactors to downstream applications lead upgradation closer, the feasibility of upgrading existing microalgal wastewater treatment into immobilized microalgal systems is thoroughly discussed. Eventually, several research directions are proposed toward the future immobilized microalgal system for microalgal wastewater treatment upgrading. Together, it appears that using immobilization for further upgrading the microalgae-based wastewater treatment can be recognized as an achievable alternative to make microalgal wastewater treatment more realistic. The information and perspectives provided in this review also offer a feasible reference for upgrading conventional microalgae-based wastewater treatment.

All About Wastewater Treatment Technologies and Application Options

Nowadays, an enormous amount of wastewater is generated, whether by industrial or human activities. Wastewater contaminated with toxic compounds can endanger the ecosystem and human health if released into the environment untreated or partially treated. For this reason, polluted industrial wastewater must be effectively treated before it is discharged into the environment. Although conventional wastewater treatment can efficiently reduce nitrogen and carbon concentrations, it is ineffective in removing so-called emerging pollutants (e.g., pharmaceuticals, pesticides, and personal care products). These compounds pass through the wastewater treatment plant unchanged and enter the environment in this way, posing a threat to nature and human life. Many of the emerging pollutants cause endocrine disruption or are carcinogenic. Efficient treatment is therefore urgently needed to remove these compounds before they enter the environment or water bodies. This special issue of the journal CLEAN – Soil, Air, Water includes the latest available technologies to treat industrial wastewater. It covers extensively the advancement in biological treatments, advanced oxidation techniques, and membrane technology to remove water pollutants. Having an easy-to-use guider manual for all the enlisted smart techniques, it also describes and discusses the emerging futuristic technologies in industrial pollutant removal from wastewater. Here, the new and emerging innovative trends in bioremediation of hazardous pollutants present in wastewater are discussed in depth. It also includes the fate of pollutants produced after the treatment process both at the laboratory scale and at the industrial scale. The special issue intrusively explores the unique biological aspects of the wastewater treatment process and highlights the advantages they provide for engineering applications in various industries. Each paper covers a different biological-based approach and examines the basic principles, practical applications, recent breakthroughs, and associated limitations. It presents an array of cutting-edge wastewater treatment research and thereafter its applications in treatment, remediation, sensing, and pollution prevention processes. The biological process for application in wastewater research has a significant impact on maintaining the long-term quality, availability, and usability of water. In this special issue, biological wastewater treatment technologies are explained. The biological processes presented in wastewater treatment processes include: 1) bioremediation of wastewater that includes aerobic treatment (oxidation ponds, aeration lagoons, aerobic bioreactors, activated sludge, percolating or trickling filters, biological filters, rotating biological contactors, and biological removal of nutrients) and anaerobic treatment (anaerobic bioreactors and anaerobic lagoons); 2) phytoremediation of wastewater that covers constructed wetlands, rhizofiltration, rhizodegradation, phytodegradation, phytoaccumulation, phytotransformation, and hyperaccumulators; and 3) mycoremediation of wastewater. The special issue describes a broad area of biological processes and water research which are considered key components for advanced water purification. It also includes the desalination technologies that remove, reduce, or neutralize water contaminants that threaten human health and/or ecosystem productivity and integrity. This special issue is mainly related to each of the main factors contributing to the removal of toxic pollutants from wastewater, namely, methods and procedures, materials (especially low-cost materials originating from industrial and agricultural waste), wastewater management, valorization possibilities of waste resulting from wastewater treatment processes, etc. This special issue is especially devoted to industrial wastewater treatment and aims to present the current state-of-the-art and innovative research that addresses these challenges, so that wastewater treatment systems can adapt and be fit for purpose, robust, and resilient for the next 100 years. It is equally beneficial for students and professors for understanding the new research advancements in this field. The main objective of this special issue is to summarize the work of the eminent scientists in this field to provide a clear but concise chapter that can be used as a quick reference for environmental engineers and researchers, and to be effectively implemented in higher education teaching undergraduate and graduate students, as well as extension and outreach.

Low salinity enhances azo dyes degradation in aerobic granular sludge systems: Performance and mechanism analysis

The biodegradation performance of azo dyes can be enhanced under low salinity conditions, but the internal biodegradation mechanism is still unclear. Aerobic granular sludge (AGS), a salt-tolerant biological wastewater treatment technology, was used in this study to explore the enhancement mechanism of acid orange 7 (AO7) degradation at low salinity level (1.0 %). Results indicated that the AGS structure and reactor performance were almost unaffected by different AO7 concentrations (5–10 mg/L). Compared with salt-free conditions, the AO7 removal efficiency was elevated by 9.9 %–19.0 % at 1.0 % salinity level, owing to the enrichment of AO7 decolorizing bacteria (e.g. Acinetobacter) and functional enzymes (e.g. FMN-dependent azoreductase). The up-regulated genes involving in the key metabolic functions (e.g. carbon metabolism and oxidative phosphorylation) promoted the electron and energy production, thereby facilitating the AO7 decolorization and degradation. These results aid understanding of the enhancement mechanism of AO7 biodegradation under low salinity conditions from macroscopic and microscopic perspectives.

Smart Modelling of a Sustainable Biological Wastewater Treatment Technologies: A Critical Review

One of the most essential operational difficulties that water companies face today is the capacity to manage their water treatment process daily. Companies are looking for long-term solutions to predict how their treatment methods may be enhanced as they face growing competition. Many models for biological growth rate control, such as the Monod and Contois models, have been suggested in the literature. This review further emphasized that the Contois model is the best and is more suited to predicting the performance of biological growth rate than the other applicable models with a high correlation coefficient. Furthermore, the most well-known models for optimizing and predicting the wastewater treatment process are response surface methodology (RSM) and artificial neural networks (ANN). Based on this review, the ANN is the best model for wastewater treatment with high accuracy in biological wastewater treatment. Furthermore, the present paper conducts a bibliometric analysis using VOSviewer to assess research performance and perform a scientific mapping of the most relevant literature in the field. A bibliometric study of the most recent publications in the SCOPUS database between 2018 and 2022 is performed to assess the top ten countries around the world in the publishing of employing these four models for wastewater treatment. Therefore, major contributors in the field include India, France, Iran, and China. Consequently, in this research, we propose a sustainable wastewater treatment model that uses the Contois model and the ANN model to save time and effort. This approach may be helpful in the design and operation of clean water treatment operations, as well as a tool for improving day-to-day performance management.

Available online sensors can be used to create fingerprints for MABRs that characterize biofilm limiting conditions and serve as soft sensors.

Membrane aerated biofilm reactors (MABRs) are a promising biological wastewater treatment technology, whose industrial applications have dramatically accelerated in the last five years. Increased popularity and fast industrial adaptation are coupled with increased needs to monitor, optimize, and control MABRs with available online sensors. Observations of commercial scale MABR installations have shown a distinctive and repetitive pattern relating oxygen purity in MABR exhaust gas to reactor ammonia concentrations. This provides an obvious opportunity for process monitoring and control which this paper investigates with the help of modeling. The relationship plots between the bulk ammonia concentration and the oxygen purity are defined as MABR fingerprint plots, which are described in the form of steady-state curves and dynamic trajectories. This study systematically investigated, analyzed, and explained the behaviors and connections of steady-state curves and dynamic trajectories with a MABR model in SUMO®, and proposed a hypothesis about utilizing the MABR fingerprint plots to characterize MABR system performance, identify the limiting factor of biofilms, and possibly develop a soft senor for MABR biofilm thickness monitoring and control.

Anaerobic electrochemical membrane bioreactor effectively mitigates antibiotic resistance genes proliferation under high antibiotic selection pressure.

The spread of antibiotics and antibiotic resistance genes (ARGs) in environments has posed potential threats to public health. Unfortunately, conventional biological wastewater treatment technologies generally show insufficient removal of antibiotics and ARGs. Bioelectrochemical systems, which can effectively degrade refractory organic pollutants via enhancing microbial metabolisms through electrochemical redox reaction, may provide an alternative for the control of antibiotics and ARGs. Herein, an anaerobic electrochemical membrane bioreactor (AnEMBR) was conducted by combining bioelectrochemical system and anaerobic membrane bioreactor to treat antibiotic-containing wastewater. The AnEMBR at open circuit showed stable CH4 production and high removal of COD and chlortetracycline (CTC) in treating 2.5-15mg/L CTC. However, increasing CTC to 45mg/L completely inhibited the methanogenesis of AnEMBR at open circuit. After applying external voltage in AnEMBR, the performances of AnEMBR were significantly improved (e.g., increased CH4 production and CTC removal). Moreover, CTC exposure significantly increased the relative abundances of ARGs in sludge, supernatant, and effluent in AnEMBR at open circuit. Applying voltage greatly attenuated the total relative abundances of ARGs in the supernatant and effluent of AnEMBR compared to those at open circuit. This could be attributed to the enrichment of tetracycline degradation gene tetX, which greatly enhanced the removal of CTC by the AnEMBR and thus reduced the selective pressure of CTC on the microorganisms in supernatant and effluent for ARGs proliferation. These results would provide an effective wastewater treatment technology for treating high-level antibiotic-containing wastewater to mitigate the potential risk of ARGs and antibiotics spread in receiving water body.

Test of Membrane Aerated Biofilm Reactors for Nitrogen Removal in Wastewater Treatment

Membrane aerated biofilm reactor, as a biological wastewater treatment technology, has been nearly mature on a commercial scale. It uses bubble-free aeration to provide oxygen for biological nitrification and wastewater degradation. A novel oxygen-permeable hollow fiber membrane (Zeelung cord) specifically designed for use in a membrane aerated biofilm reactors (MABR). These fibers are organized into bundles, which are wrapped around the reinforcing core to increase strength. This permeable membrane allows oxygen to diffuse into the attached biofilm, which directly leads to the biological oxidation of pollutants in the wastewater. This study aimed to determine the nitrification and oxygen transfer capacity of Zeelung fibers used in the MABR system. The effects of various C/N ratios (in the range of 1.0 to 3.0) on the membrane modules were studied using three laboratory-scale reactors over the course of 165 days. In this test, the average removal efficiency of COD can reach 74% under selected conditions, up to 90%. Meanwhile, the average nitrification rate is 3.9 g/d/m2, the average ammonia removal rate is 90%, and the maximum value can reach 99%. In addition, the oxygen transfer rate of the fiber in the liquid phase was 19.65 g/d/m2. The experiment also indicated that the nitrification rate is directly proportional to the transfer flux of oxygen and is related to the content of dissolved oxygen in the water. The nitrification rate can be controlled by controlling the concentration of dissolved oxygen in water, thus affecting the removal rate of ammonia nitrogen.

Technological Advances in Winery Wastewater Treatment: A Comprehensive Review

The commercial production of wine is directly linked to the use of large amounts of fresh water coupledwith the generation of copious amounts of wastewater containing significant amounts of organic andinorganic substances. The impact of this waste stream on the environment has required the wine industryto implement certain protocols in wastewater management to comply with respective effluent dischargeregulations as set out by local authorities. Reduced accessibility to good quality water resources in recentyears has forced wineries to consider more efficient wastewater management strategies to improve waterrecovery and re-use, thereby promoting more sustainable wine production and minimizing the impact onstressed water resources. This review presents a comprehensive overview of established and emerging,physicochemical, biological, advanced oxidation and hybrid wastewater treatment technologies specificallyapplicable to the wine producing industry. Herein, winery wastewater composition and treatmenttechniques, environmental implications, knowledge gaps, technological operational challenges, alternativedisposal and recycling options of treated winery wastewater are critically evaluated.

RESEARCH ON IMPROVEMENT OF THE METHOD OF PERIODIC AERATION OF WASTEWATER

The aeration process is a key part of biological wastewater treatment technology. But, paradoxically, during the existence of this technology, it has not changed significantly. The process of aeration of wastewater remains the largest consumer of electricity in the entire complex of treatment facilities. The possibility of adjusting the duration of the aeration cycle depending on the "explosive" change in the amount of contaminants was stated. In this case, the system must respond to this "perturbation" and adjust the duration of the aeration cycle to provide the necessary oxygen regime of biological oxidation of contaminants. The research data on the method of periodic aeration based on a comparison of the concentration of oxygen in the liquid to be cleaned and in the gases leaving after aeration are presented. The basic principle is that the aeration system continues to supply oxygen, which is no longer able to diffuse into the aerated liquid, and comes to the surface, bypassing the process of mass transfer. The experimentally established method of adjusting the duration of aeration periods for implementation in one aeration tank can be applied to a whole group of aeration tanks. Using the method in the optimal mode for each of the specified number of aeration tanks is impossible without the use of a microprocessor. Therefore, a control method was developed that allows the application of a fundamentally new algorithm for periodic aeration. This algorithm allows to increase the growth of activated sludge and to increase the efficiency of wastewater treatment. To assess the possibility of stabilizing the operation of certain aeration tanks, in the implementation of intermittent aeration by the concentration of oxygen in the liquid, a model example was considered, from which follows the differential equation of oxygen balance in the liquid. The study of this equation for stability and behavior in the phase plane makes it possible to choose the conditions under which the periodic aeration algorithm will be the most efficient in terms of purification and energy consumption. Theoretical calculation gave a mathematical justification for the experimental data. Based on numerical calculations, the condition of optimal operation of the aeration system for a group of aeration tanks is derived. Thus, it was found that the optimal concentration of oxygen in the liquid at which to start aeration is 0.06-0.12 mg / dm3. Periodic aeration with a period of 30 minutes makes it possible to maintain a stable gradient of oxygen concentrations in the liquid. The productivity of treatment plants according to the developed algorithm of controlled aeration, in accordance with the concentration of oxygen in the liquid to be cleaned, ensures the rational use of electricity.

Positive effects of zeolite powder on aerobic granulation: Nitrogen and phosphorus removal and insights into the interaction mechanisms

Aerobic granular sludge is considered one of the most promising biological wastewater treatment technologies of the 21st century. However, the long granulation time and poor treatment effect on N and P have severely limited its popularity and large-scale application. In this study, we systematically examine the strengthening effects of zeolite powder on granulation, N and P removal, and their interaction mechanisms. The addition of zeolite powder decreased sludge granulation time to 18 d, and improved average N and P removal rates by 4.48% and 2.22%, respectively. The multi-pore and nutrient-rich environment of the zeolite powder is beneficial for maintaining microbial activity and granular stability. Moreover, its adsorption to N and P enriches their respective removal strains, improving their removal efficiency.

The High Water Plants Water Road in Cleaning

The ecology of high-water plants such as pistachio, euchronia, azolla forms the basis for improving biological wastewater treatment technology. For the first time in the Andizhan region of the Republic of Uzbekistan, it was found that high-altitude algae can be used by the method of biological treatment of municipal wastewater. the results of the study, we used biological treatment of high-water plant species such as pistia (Pistia stratiotes), Euchornia crassipes Solms, azolla (Azolla coroliniana Willd), with the observations of the dynamics of rapid growth and development at high concentrations. We developed a Pistia stratiotes, which is scientifically grounded in improvement, and was recommended for reproduction under laboratory conditions.

Advances in biological wastewater treatment technology of microalgae.

Microalgae has the advantages of high growth rates, high cellular lipid productivity and capability to bio-sequester carbon dioxide, and thus being widely studied as a new generation of biomass energy. The sustained investment in freshwater resources and nutrients during its growth period, however, is a major obstacle to large-scale cultivation. Combining a microalgae culture system with wastewater treatment is an economically viable wastewater resource utilization strategy. Based on the utilization mechanism of nutrients such as nitrogen and phosphorus during the growth of microalgae, we reviewed the application of microalgae in the biological wastewater treatment. The removal/inhibition ability of organic and inorganic compounds, heavy metals and pathogens were analyzed. The effects of environmental factors including the initial nutrient concentration, light, temperature, pH, salinity and gas exchange on the growth and metabolism of microalgae were investigated. In addition, combined with the problems faced by the large-scale application of microalgae, the application prospect and development direction of microalgae wastewater treatment were prospected, with the aim to provide references for the construction and management of water ecosystems.

Establishing a decision-support system for eco-design of biological wastewater treatment: A case study of bioaugmented constructed wetland

Deep treatment is a common approach to enhance pollutant removal for biological wastewater treatment technologies (BWTTs), and life cycle assessment (LCA) holds substantial advantages to support process optimization. However, there lacks of LCA-based benchmarks that cover human-nature nexuses and stakeholder involvement, which limits the guidance and eco-design of BWTTs. This study proposed a decision-support system (DSS) by linking LCA with Water Quality Model and Conjoint Analysis. Three major findings were identified based on a demonstrative case (constructed wetland bioaugmented by dosing different microbial inocula): (1) Increasing bacterial intensities would achieve net environmental improvement, but it might not apply to all cases; (2) Making full use of natural self-purification capacity could partly replace the functions of BWTTs; (3) Stakeholders would concern aquatic environmental improvement when receiving river that had limited environmental capacity. Overall, the DSS provided a data-driven platform for screening options before determinations were made to constrain wastewater treatment sustainability.

Agroindustrial Wastewater Treatment with Simultaneous Biodiesel Production in Attached Growth Systems Using a Mixed Microbial Culture

The use of cyanobacteria in biological wastewater treatment technologies can greatly reduce operation costs by combining wastewater bioremediation and production of lipid suitable as biodiesel feedstock. In this work, an attached growth system was employed to achieve the above-mentioned dual objective using a mixed microbial culture dominated by Leptolyngbya and Limnothrix species in diverse heterotrophic consortia. Kinetic experiments on different initial pollutant concentrations were carried out to determine the ability of the established culture to remove organic load (expressed by d-COD, dissolved-Chemical Oxygen Demand), N and P from agroindustrial wastewaters (dairy, winery and raisin). Biomass and oil productivity were determined. It was found that significant removal rates of nutrients were achieved in all the wastewaters examined, especially in that originated from winery in which the highest d-COD removal rate (up to 97.4%) was observed. The attached microbial biomass produced in winery wastewater contained 23.2% lipid/biomass, wt/wt, which was satisfying. The growth in the dairy wastewater yielded the highest attached biomass productivity (5.03 g m−2 day−1) followed by the mixed effluent of winery-raisin (4.12 g m−2 day−1) and the winery wastewater (3.08 g m−2 day−1). The produced microbial lipids contained high percentages of saturated and mono-unsaturated fatty acids (over 89% in total lipids) in all substrates examined. We conclude that the proposed attached growth photobioreactor system can be considered an effective wastewater treatment system that simultaneously produces microbial lipids suitable as biodiesel feedstock.