Biological Water Treatment Research Articles

Biological treatment of eutrophicated lagoon water with Tetradesmus dimorphus under ambient conditions: a sustainable alternative for lipid production

Biological treatment of eutrophicated lagoon water with Tetradesmus dimorphus under ambient conditions: a sustainable alternative for lipid production

Machine learning-based input-augmented Koopman modeling and predictive control of nonlinear processes

Koopman-based modeling and model predictive control have been a promising alternative for optimal control of nonlinear processes. Good Koopman modeling performance significantly depends on an appropriate nonlinear mapping from the original state-space to a lifted state space. In this work, we propose an input-augmented Koopman modeling and model predictive control approach. Both the states and the known inputs are lifted using two deep neural networks (DNNs), and a Koopman model with nonlinearity in inputs is trained within the higher-dimensional state space. A Koopman-based model predictive control problem is formulated. To bypass non-convex optimization induced by the nonlinearity in the Koopman model, we further present an iterative implementation algorithm, which approximates the optimal control input via solving a convex optimization problem iteratively. The proposed method is applied to a chemical process and a biological water treatment process via simulations. The efficacy and advantages of the proposed modeling and control approach are demonstrated.

Solvent-free synthesis of TiO2 nanoparticles embedded MWCNTs with enhanced photocatalytic activity for bacterial disinfection

Sustainable energy has been widely researched to address issues caused by population growth and rapid industrialization. Among them, photocatalysis using solar energy has been considered promising. We developed a hybrid photocatalyst by combining titanium dioxide (TiO2) with carbon nanotubes (CNTs), known for their excellent adsorption performance. A unique structure encapsulating TiO2 nanoparticles (NPs) within the inner space of multi-walled carbon nanotubes (MWCNTs) was developed via a facile, solvent-free method, conforming to green chemistry principles. Except purification and modification of the CNTs, the particle formation process is solvent-free, making this method remarkably simple and environmentally friendly. This arrangement enhances stability and recyclability, maintaining over 90 % efficiency up to the 3rd cycle. X-ray diffraction (XRD) analysis confirmed that the TiO2 NPs exhibited a crystalline phase, forming exclusively anatase. The defects in the outer walls of the MWCNTs in the composite, coupled with their large specific surface area and dangling bonds, endow them with high adsorption capacity and photocatalytic activity when combined with TiO2 NPs. The MWCNTs@TiO2 composites achieved over 99 % inactivation of Escherichia coli in 60 min and bacteriophage MS2 in 30 min, along with dye adsorption/decomposition. This method offers a distinctive platform for photocatalytic degradation in biological applications and water treatment.

Droplet Electrophoresis with Internal Free Ions: Effect of Permittivity Changes in the Electric Double Layer.

Droplet electrophoresis (EP) is of interest in biological systems, microfluidics, and separation techniques. We investigate EP of an oil droplet that contains free ions and is stabilized in an electrolyte solution through an amphoteric surfactant. The presence of mobile ions within the droplet leads to the creation of a distinct nonzero space charge density inside the droplet and consequently, formation of an inner EDL inside the droplet in addition to the traditionally considered outside EDL. While we assume the permittivity inside the inner EDL to remain constant, we consider both the case of constant and variable permittivity in the outer EDL. Our findings demonstrate a change in the droplet direction of motion in the electric field when transitioning from acidic to alkaline pH, regardless of permittivity and ionic strength in both oil and electrolyte. We further find a significant reduction in the magnitude of droplet velocity in the case of a variable permittivity due to reduction of the local space charge density within the EDL surrounding the droplet. When decreasing the viscosity ratio of the oil to the electrolyte, in all cases we find a reduction in droplet velocity. This decline is attributed mostly to the formation and strength of a vortex around the droplet. We finally demonstrate that with constant permittivity in the outer EDL, the variation in κaouter has a more significant effect on the droplet's EP velocity than altering κainner. However, in cases where the body forces inside of the droplet dominate, minor changes in the outer electrolyte concentration have no influence on the droplet motion, which is relevant for biological colloids that can contain significant free internal charges. Our results are important for the manipulation of biological colloids, water and waste treatment such as lubricant removal from processing streams.

Systematic Review of Poultry Slaughterhouse Wastewater Treatment: Unveiling the Potential of Nanobubble Technology

Aeration is crucial for the biological decomposition of organic compounds in wastewater treatment. However, it is a highly energy-intensive process in traditional activated sludge systems, accounting for 50% to 75% of a plant’s electricity consumption and making it a major cost driver for wastewater treatment plants. Nanobubbles (NBs), characterized by their tiny size with diameters less than 200 nm, have emerged as a potential alternative to the low efficiency of aeration and high sludge production in aeration systems. NBs proved effective in removing COD and other pollutants from wastewater. For example, when applied in flotation, aeration, and advanced oxidation, NBs achieved up to 95%, 85%, and 92.5% COD removal, respectively. Considering the recent advancements in wastewater treatment, a compelling need arises for a thorough investigation of the effectiveness and mechanisms of nanobubbles in this field. This systematic review summarizes recent advancements in understanding nanobubbles (NBs) and their unique properties that enhance physical, chemical, and biological water and wastewater treatment processes. Moreover, this study reviews various methods for generating NBs and provides an in-depth review of their applications in wastewater treatment, with a particular focus on poultry slaughterhouse wastewater (PSW) treatment.

Incubation and Larval Development Durations of Sterlet (A. ruthenus LINNAEUS 1758) in River Water Rearing under Near-Natural Conditions

Day-degrees [°D], also known as accumulated thermal units (ATUs), have been used to predict the duration of early development for fish. For most sturgeon species, the available data in the literature were determined under temperature-constant conditions. However, there is a lack of information on ATUs of early development for sturgeons under natural or near-natural temperature conditions. The aim of this study was to observe the duration of incubation and the duration from hatch until feeding of sterlets (Acipenser ruthenus) under near-natural conditions. This study was embedded within the LIFE-Sterlet and LIFE-Boat 4 Sturgeon project and data were gathered from the year 2017 to 2023. The rearing of fish larvae took place in the project hatchery container with Danube water without biological, chemical, or thermal water treatment to simulate natural conditions. Temperatures [°C] were monitored on a daily basis and day-degrees were calculated by summing the temperature over time. Results indicated slower larval development than described in the literature. Hatching started earliest after 7 days at 106 °D and latest after 151 °D. Feeding started between 155 and 271 °D. The findings of this study provide valuable insights into the temperature-dependent development of sterlet larvae under near-natural conditions and can assist in the design of optimal rearing of sturgeons for conservation efforts.

Mathematical Model of Oxygen Regime Analysis in a Bioreactor

Purpose. Today, aeration tanks are widely used to treat industrial and municipal wastewater. Assessing the efficiency of water treatment in aeration tanks under different operating conditions is an important task. To solve this problem, it is necessary to have mathematical models that allow to quickly obtain data on the effect of treatment in aeration tanks. The main objective of this work is to develop a numerical box model to determine the efficiency of wastewater treatment in an aeration tank. Methodology. For mathematical modeling of the biological wastewater treatment process in a bioreactor, zero-dimensional material balance equations are used, which are written in relation to the concentration of substrate, activated sludge, and dissolved oxygen in wastewater. The Monod model is used to calculate the substrate oxidation process. The Euler method is used to integrate the modeling equations. A simplified model of biological water treatment in a bioreactor is considered, which makes it possible to obtain an analytical solution to the problem. The obtained analytical expression makes it possible to quickly determine the change in the concentration of dissolved oxygen in wastewater depending on the change in the concentration of activated sludge in the bioreactor. The constructed numerical model makes it possible to determine the dynamics of changes in the concentration of contaminants, activated sludge and oxygen in wastewater during their stay in the bioreactor. Findings. A tool for theoretical evaluation of the efficiency of biological wastewater treatment in an aeration tank is proposed. A numerical model has been built that allows determining the concentration of dissolved oxygen, substrate and activated sludge at the outlet of the aeration tank. Originality. An effective numerical model has been developed that allows to quickly calculate the dynamics of wastewater treatment in a bioreactor and, based on this information, to evaluate the efficiency of the reactor. Practical value. The constructed mathematical model can be useful in the reconstruction of biological wastewater treatment facilities, as well as at the design stage of bioreactors to take into account their operation under different operating conditions. A computer program has been developed that implements the constructed numerical model. The results of a computer experiment are presented.

Performance assessment of Al-Rustumiah wastewater treatment plant using multivariate statistical technique

An attempt has been made to assess the performance of the third expansion of the Al-Rustamiya wastewater treatment plant (WWTP). This plant serves approximately 1,500,000 people in east Baghdad city, the capital of Iraq, and the increase of the population in this part of the city has reached about 4 million which led to deterioration in their effluents quality. Furthermore, the plant has no improvement on their processing units. Al-Rustamiya WWTP uses a biological water treatment method known as the activated sludge process with an average wastewater treatment of about 300 million liters. In the present paper, a wastewater quality data of ten years has been subjected to a multivariate statistical technique to identify the most important factors that affect the performance of the plant and estimating its efficiency. The data was collected and examined by the central laboratory of the Al-Rustamiya wastewater treatment plant in the mayoralty of Baghdad. Factor Analysis has been used to assess the important water quality parameters: pH, Total Suspended Solids, Biochemical Oxygen Demand (BOD), and Chemical Oxygen Demand (COD). The results revealed that the major factor that affects the performance is the organic load of raw wastewater and the removal efficiency of the WWTP. Furthermore, the results present that the performance of the current plant system is acceptable exclude for the removal efficiency of BOD below the prescribed limit. As well as, The BOD and COD correlation can evaluate wastewater treatment plant efficiency, aid in prompt intervention, and monitor harmful substances.

Comparing DNA isolation and sequencing strategies for 16S rRNA gene amplicon analysis in biofilm containing environments

Bacteria are primarily responsible for biological water treatment processes in constructed wetland systems. Gravel in constructed wetlands serves as an essential substrate onto which complex bacterial biofilms may successfully grow and evolve. To fully understand the bacterial community in these systems it is crucial to properly isolate biofilms and process DNA from such substrates. This study looked at how best to isolate bacterial biofilms from gravel substrates in terms of bacterial richness. It considered factors including the duration of agitation during extraction, extraction temperature, and enzyme usage. Further, the 16S taxonomy data subsequently produced from Illumina MiSeq reads (using the SILVA 132 ribosomal RNA (rRNA) database on the DADA2 pipeline) were compared with the 16S data produced from Oxford Nanopore Technologies (ONT) MinION reads (using the NCBI 16S database on the EPI2ME pipeline). Finally, performance was tested by comparing the taxonomy data generated from the Illumina MiSeq and ONT MinION reads using the same (SILVA 132) database. We found no significant differences in the effective number of species observed when using different bacterial biofilm detachment techniques. However, enzyme treatment enhanced the total concentration of DNA. In terms of wetland community profiles, relative abundance differences within each sample type were clearer at the genus level. For genus-level taxonomic classification, MinION sequencing with the EPI2ME pipeline (NCBI database) produced bacterial abundance information that was poorly correlated with that from the Illumina MiSeq and DADA2 pipelines (SILVA132 database). When using the same database for each sequencing technology (SILVA132), the correlation between relative abundances at genus-level improved from negligible to moderate. This study provides detailed information of value to researchers working on constructed wetlands regarding efficient biofilm detachment techniques for DNA isolation and 16 s metabarcoding platforms for sequencing and data analysis.

Contamination Characteristics，Detection Methods，and Control Methods of Antibiotic Resistance in Pharmaceutical Wastewater

Pharmaceutical industry wastewater contains a large number of emerging pollutants such as antibiotics， antibiotic resistant bacteria （ARBs）， and antibiotic resistance genes （ARGs）. The present biological water treatment processes cannot effectively remove these pollutants. Eventually， they are discharged into various water bodies or penetrate into soil with the effluent， causing environmental pollution and affecting human health. Therefore， exploring the pollution characteristics of antibiotics， ARBs， and ARGs in pharmaceutical wastewater and knowing the methods to detect and control antibiotic resistance pollution in wastewater are crucial for reducing the contamination of antibiotics and ARGs and assessing the ecological risks of antibiotic resistance. Aiming at the problem of antibiotic resistance pollution in a pharmaceutical wastewater treatment plant （PWWTPs）， the pollution status of antibiotics， ARBs， and ARGs in pharmaceutical wastewater was discussed. Different assessment methods of antibiotic resistance in pharmaceutical wastewater were summarized. Finally， the wastewater treatment technologies commonly used to remove antibiotics and ARGs in PWWTPs were summarized in order to provide a theoretical basis for the ecological risk assessment and scientific control of antibiotics and ARGs in the environment.

The method of complex biological water treatment in aquaponic recirculation systems

The article discusses the results of experimental research work on the development of technical solutions aimed at creating an integrated innovative biotechnology for recycled water treatment in recirculating aquaculture systems. Schemes and descriptions of experimental units using the multitrophic approach when creating water treatment systems are given. The system is completed according to the principle of integration into a single multitrophic system of spatially delimited biomodules with various types of hydrobionts, where particular types of organisms serve as a food base for subsequent trophic levels. As a result of trophic chains, phytoplankton and zooplankton are cultivated and used as starter live food when rearing juvenile fish. Natural food base contributes to the production of high-quality viable fish stock, which is essential for commercial fish farming. The use of tiered units can significantly reduce the need for production space. Polyculture cultivation of various species of fish, crustaceans, and mollusks together with hydroponic plants allows to diversify production for obtaining additional profit and reducing the risks. Cultivation of high-value fish species (e.g. sturgeon) or crustaceans (Australian red claw) together with less valuable cyprinids, tilapia or African catfish allows to promote products in different market segments.

Benefitting from Biological Filter Media

Expo-Net Danmark’s Bio-Blok is a versatile biological water treatment filter media with cost and performance benefits.

Nitrogen-sparging assisted anoxic biological drinking water treatment system.

Existing heterotrophic denitrification reactors rely on microorganisms to consume dissolved oxygen (DO) and create conditions suitable for denitrification, but this practice leads to excessive microbial growth and increased organic carbon doses. An innovative reactor that uses nitrogen gas sparging through a contactor to strip DO was developed and tested in the lab. It reduced influent nitrate from 15 to <1 mg/L as N with nitrite accumulation <1 mg/L as N. It maintained a consistent flow rate and developed minimal headloss, making it easier to operate than the denitrifying dual-media filter that was operated in parallel. Gravel, polyvinyl chloride pieces, and no packing media were assessed as options for the nitrogen-sparged contactor, and gravel was found to support denitrification at the highest loading rate and was resilient to nitrogen-sparging shutoffs and intermittent operation. This innovative reactor appears promising for small drinking water systems.

The challenges of aquaculture in protecting the aquatic ecosystems in the context of climate changes

The paper discusses the current prognoses of aquaculture development worldwide putting an emphasis on its effect on the environment and the issue of the protection of water reservoirs in different countries. Water consumption in diversified aquaculture systems is presented herein as well as the characteristics of the mechanical and biological water treatment methods in fish farms, with particular attention paid to the recirculating water systems. New aquaculture technologies using post-production waters are presented. The paper provides a discussion on the contribution of aquaculture to the global greenhouse gas emissions and the means of limiting this emission. The effect of climate change on aquatic ecosystems is presented in the context of the changes of the aquaculture production profile. The paper includes a brief presentation of the methods of mitigating the changes with respect to contamination of aquatic ecosystems as well as climate change. Reducing the water footprint can be achieved through selective breeding, species diversification and implementation of more technologically advanced aquaculture systems such as: integrated multi-trophic aquaculture, aquaponics and recirculation systems in aquaculture. The need for certification of fish farms with water recirculation systems is justified in the paper. The issues addressed herein are summarised and the main areas for extending the research promoting preservation of aquatic ecosystems in aquaculture are presented.

Electrochemical applications in RAS: A review

AbstractElectrochemical water treatment for recirculating aquaculture systems (RAS) is a promising approach for replacing the biological water treatment methods and establishing a new RAS generation with improved cost‐effectiveness, lower environmental footprint, and no start‐up periods. On top of ammonia oxidation directly into N2(g), electrochemical oxidation results in effective disinfection, and in the removal of organic matter, including specific organic constituents such as off‐flavour agents. The paper provides an overview of incentives for the implementation of electrochemical methods in RAS. It covers the electrochemical principles relevant to aquaculture applications, the effects of physical and chemical parameters, as well as design considerations. In addition, the research performed to date for integrating electrochemical methods in RAS operation is reviewed and the variety of designs and operational configurations described. The electrochemical water treatment is perceived beneficial over biological water treatment especially in cold saline‐seawater aquaculture (e.g., Atlantic salmon), where large nitrification reactors are required and the large water consumption for purging processes can be curtailed. It is also beneficial for the culturing of nitrate‐sensitive species (e.g., L. vannamei). The paper points out the gaps to be overcome for allowing commercial breakthroughs based on electrochemical water treatment, including the need for expanding the practice and improving engineering practices by operating pilot systems for growing fish at both small and large scales; adjusting of electrochemical cell designs for reducing both capital and operational costs; developing full‐proof malfunction‐free dechlorination strategies, and evaluating and optimizing the disinfection abilities for inactivating typical pathogens in aquaculture.

A novel method to estimate biofilm activity based on enzymatic oxygen release from hydrogen peroxide decomposition

Biofilm is central for biological water treatment processes in recirculating aquaculture systems (RAS). A lack of suitable methods for quantifying biofilm activity, however, makes it difficult to assess and compare the microbial status of biofilm. This type of information of the biofilm will be useful to assess the colonization status of nitrifying biocarriers or to evaluate the effect of disinfectants on the biofilm activity.Here we introduce a novel assay for rapid assessment of microbial activities in the biofilm attached on bioelements from a RAS biofilter. The assay consisted of an intermittent respirometer platform where biofilter elements were exposed to 10 mg/L hydrogen peroxide (H2O2) for 1 h, following concurrent measurements of oxygen release from the decomposition of H2O2 caused by biofilm-associated enzymes. A different number of colonized, mature bioelements from a moving bed biofilter in a freshwater RAS were tested with repeated H2O2 exposure, and compared against their autoclaved forms. A substantial increase in dissolved oxygen (DO) concentration (0.92–2.31 mg O2/L) occurred with mature bioelements during 1 h of H2O2 exposure, compared to small amounts of DO release (≤0.27 mg O2/L) with autoclaved bioelements. This substantiates that H2O2 decomposition by biofilm is mainly governed by microbial enzymatic activities. A monomolecular model fitted well with the observed oxygen release profiles of tested mature bioelements after H2O2 exposure (R2 > 0.98). The kinetic rate constant of net oxygen release (kor, h−1) was proportional (R2 for linear fit = 0.99) to the number of mature bioelements tested. Repeated exposure of H2O2 to the same bioelements did not change kor, which indicates that 10 mg/L H2O2 with an exposure time of 1 h does not suppress enzymatic activity in biofilm. Our study provides a new rapid method that allows simple quantification of microbial activity in biofilm samples from aquaculture systems, which could potentially be also applied to study biofilm from wastewater treatment plants and other industries.

Water and Nutrient Recovery for Cucumber Hydroponic Cultivation in Simultaneous Biological Treatment of Urine and Grey Water

Water and nutrient deficiencies in soil are becoming a serious threat to crop production. Therefore, usable water and nutrient recovery from wastewater, such as urine and grey water, should be considered. In this work, we showed the possibility of using grey water and urine after processing in an aerobic reactor with activated sludge in which the nitrification process takes place. The resulting liquid (nitrified urine and grey water, NUG) contains three potential factors that can adversely affect plant growth in a hydroponic system: anionic surfactants, nutrient deficits, and salinity. After dilution and supplementation with small amounts of macro- and micro-elements, NUG was suitable for cucumber cultivation. Plant growth on this modified medium (enriched nitrified urine and grey water, NUGE) was similar to that of plants cultivated on Hoagland solution (HS) and reference commercial fertilizer (RCF). The modified medium (NUGE) contained a significant amount of sodium (Na) ions. Therefore, typical effects of salt stress were observed in cucumber plants, including reduced chlorophyll levels, slightly weaker photosynthesis parameters, increased H2O2 levels, lipid peroxidation, ascorbate peroxidase (APX) activity, and proline content in the leaves. In addition, reduced protein levels were observed in plants treated with recycled medium. At the same time, lower nitrate content in tissues was found, which may have resulted from their intensive use by nitrate reductase (NR), the activity of which significantly increased. Although cucumber is a glycophyte, it grew very well in this recycled medium. Interestingly, salt stress and possibly anionic surfactants promoted flower formation, which in turn could positively affect plant yield.

Introduction of oxygen vacancy to Bi2Mn4O10 supported by nickel foam for 1O2 dominated metronidazole degradation under dielectric barrier discharge plasma

Antibiotics in surface water adversely affect food safety and aquatic ecosystem, which hinder biological water treatment, and advanced oxidation technology (AOPs) is of great significance. This study achieved nitroimidazole antibiotic metronidazole (MNZ) removal in a dielectric barrier discharge plasma (DBDP) process. A ternary Bi2Mn4O10/NiF (BMON) was synthesized via microwave-assistant to enhance the DBDP process. Compared with Bi2Mn4O10, BMON has a more stable structure with lower ion dissolution but higher oxygen vacancy (Vö) content. The DBDP process generates active species, and O2⋅− acts as an intermediate in forming 1O2⋅− to degrade MNZ through multipath. The cycle of lattice oxygen (OL)/O2 and Mn+/M(n−1)+ maintain the charge balance on the BMON surface, during which the transformation of Vö and 1O2 improve the catalytic efficiency. Furthermore, MNZ possible degradation pathways were proposed by DFT calculations and ESI-QTOF-MS detection. The DBDP/BMON process exhibited great potential for heterogeneous catalytic in nitroimidazole antibiotic degradation.

Analysis of urban communal water supply

Currently, the incomplete provision of wastewater treatment facilities for municipal and industrial industries, their proximity to canals, collectors, river banks and other water bodies, leads to significant pollution of water resources. On the basis of the Action Strategy for the five priority areas of development of the Republic of Uzbekistan for 2017-2021, paragraph 4.3 reads: defined as strategic tasks [1; 2]. It is important to reduce the impact of municipal wastewater on open water bodies, to carry out scientific research on environmental protection. At the same time, the use of water and aquatic plants in the biological treatment of water is about 80% effective in the treatment of organic contaminants in wastewater, 40% in the physicochemical method and about 30% in the mechanical method [3].

Comparative Study of Conventional and Biological Water Treatment

Comparative Study of Conventional and Biological Water Treatment