Reactor For Wastewater Treatment Research Articles

Modelling competitive adsorption of organic micropollutants onto powdered activated carbon in continuous stirred tank reactors for advanced wastewater treatment

This work investigates the validation and application of a competitive model approach for full-scale wastewater treatment plants (WWTP) with external recirculation of partially loaded powdered activated carbon (PAC) for removal of organic micropollutants (OMP). It is based on the ideal adsorbed solution theory (IAST) for multisolute mixtures combined with calibration of fictive organic components and correction of single-solute model parameters for OMP by use of the tracer model (TRM). Adsorption kinetics are represented by a pseudo first order reaction (PFO) and compared to mass transfer calculated with the homogenous surface diffusion model (HSDM). Model validation with operational data from two different WWTPs showed a strong dependency of model results on the batch sample quality used for model calibration. In contrast, the kinetic approach is of less importance for predicting full-scale OMP removal with long PAC sludge retention times. Further model application demonstrated that external PAC recirculation significantly improves the OMP removal with regard to both adsorption capacity and compensation of competitive effects of Dissolved Organic Carbon (DOC).

High-performance internal circulation anaerobic granular sludge reactor for cattle slaughterhouse wastewater treatment and simultaneous biogas production

This research investigates the efficacy of a high-performance pilot-scale Internal Circulation Anaerobic Reactor inoculated with Granular Sludge (ICAGSR) for treating cattle slaughterhouse wastewater while concurrently generating biogas. The primary objective is to assess the efficiency and performance of ICAGSR in terms of organic pollutant removal and biogas production using granular anaerobic sludge. The research methodology entails operating the ICAGSR system under ambient conditions and systematically varying key parameters, including different Hydraulic Retention Times (HRTs) (24, 12, and 8 h) and Organic Loading Rates (OLRs) (3.3, 6.14, and 12.83 kg COD/m³. d). The study focuses on evaluating pollutants’ removal and biogas production rates. Results reveal that the ICAGSR system achieves exceptional removal efficiency for organic pollutants, with Chemical Oxygen Demand (COD) removal exceeding 74%, 67%, and 68% at HRTs of 24, 12, and 8 h, respectively. Furthermore, the system demonstrates stable and sustainable biogas production, maintaining average methane contents of 80%, 76%, and 72% throughout the experimental period. The successful operation of the ICAGSR system underscores its potential as a viable technology for treating cattle slaughterhouse wastewater and generating renewable biogas. In conclusion, this study contributes to wastewater treatment and renewable energy production by providing a comprehensive analysis of the ICAGSR system’s hydrodynamic properties. The research enhances our understanding of the system’s performance optimization under varying conditions, emphasizing the benefits of utilizing ICAGSR reactors with granular sludge as an effective and sustainable approach. Identifying current gaps, future research directions aim to further refine and broaden the application of ICAGSR technology in wastewater treatment and renewable energy initiatives.

Computational modeling of microalgal biofilm growth in heterogeneous rotating algal biofilm reactors (RABRs) for wastewater treatment

Rotating algal biofilm reactors (RABRs) are innovative systems designed to cultivate microalgae biofilms efficiently. In this paper, we have developed a novel mathematical model to accurately capture the growth dynamics of algae biofilms within RABR. By considering the spatial heterogeneity of the RABR, we introduce a PDE-based model that addresses the spatial variations across the substratum, enabling a more accurate simulation of biofilm growth in RABRs. The photosynthesis process is modeled through reactive kinetics, driving the growth of the algae biofilm. To analyze the system's behavior, we employ finite difference numerical methods to solve the complex PDE model. We then conduct extensive numerical simulations to understand algae biofilm growth in the RABR environment under various operational factors and environmental conditions. One primary focus in these simulations is to investigate the impact of various harvesting strategies, harvesting frequencies, light intensity, and light exposure on the overall biomass productivity of the algae biofilm. The numerical results provide valuable insights into optimizing algae biofilm growth and designing harvesting techniques in RABR systems. Our proposed novel mathematical model provides an effective platform for the theoretical investigation and design of RABRs for wastewater treatment.

On the geometry and material stability of tubular PVDF-TiO2 static mixer membrane contactors for photocatalytic ozonation of micropollutants

The prevention of ozone hotspots in ozonation reactors for wastewater treatment is essential for effective degradation of micropollutants without forming harmful by-products. Membrane contactors can provide a bubble-free ozonation process that is able to decrease by-product formation, e.g., bromate formation in bromide-charged wastewater. Furthermore, the geometry of the reactor influences the distribution of dissolved ozone in a membrane contactor. Turbulence promoters can significantly decrease ozone hotspots and increase ozone mass transfer into wastewater. This work presents a fabrication methodology to produce PVDF-TiO2 helical static mixer membranes using the rotation-in-a-spinneret technology. Static mixer membranes combine the functionality of a membrane contactor and a static mixer in a single component. Furthermore, the PVDF matrix is doped with TiO2 particles as photocatalyst. Thus, we present a membrane-based photocatalytic ozonation process to increase the concentration of hydroxyl radicals for degradation of micropollutants under UV radiation. Static mixer membranes increase the ozone mass transfer coefficient by 70% compared to conventional hollow fiber membranes. Furthermore, the specific photocatalytic degradation rate of methylene blue increases by 50% using static mixer membranes. However, this work also reveals a lack of long-term stability of PVDF-TiO2 membranes in the corrosive environment of photocatalytic ozonation. The molecular weight of PVDF decreases by 11% after use in photocatalytic ozonation resulting in a loss of mechanical stability of the membranes. Similar material concepts are required based on ceramic materials which avoid wetting of the porosity.

Enhancing wastewater treatment with a novel separated algae membrane oxygenated activated sludge reactor

In this investigation, a separated algae membrane oxygenated activated sludge wastewater treatment reactor was developed. During the phase of aeration pump absence, the system, featuring a separated algae biofilm oxygenation activated sludge mechanism with an internal reflux ratio of 5 and a C/N ratio of 10, demonstrated remarkable efficiency in pollutant removal. Specifically, it achieved COD, TN, NH4+-N, and TP removal rates of 96.6 %, 81.9 %, 98.6 %, and 95.5 %, respectively. Despite a decline in dissolved oxygen (DO) during the transition of wastewater from the algae membrane reactor to the aerobic tank, the internal circulation reflux ratio of 5 ensured that the oxygen-enriched effluent from the algae membrane photoreactor maintained a stable DO level in the aerobic tank, ranging from 1.5 to 2.0 mg/L, thus meeting the oxygen demand of the activated sludge. Alterations in the aeration method had a notable impact on the diversity of the microbial community. Notably, the community shifted from bacteria adapted to intermittent aeration to those acclimated to internal recirculation for oxygen supply. The dominant microbial position was reinforced, with the Patescibacteria phylum and the norank_f__norank_o __ Saccharimonadales genus emerging as the dominant entities within the community. Under internal circulation reflux aeration, filamentous green algae persisted, resulting in a significant increase in biomass and chlorophyll content by 3.07 and 2.93 times, respectively. Furthermore, microalgae exhibited elevated protein and polysaccharide content, which increased by 3.14 and 3.16 times, respectively, due to the influence of the internal circulation reflux process, promoting the maturation of the algae membrane.

Biosand Reactors for Municipal and Industrial Wastewater Treatment: Status Quo, Challenges and Opportunities

Biosand reactors (BSRs), alternatively known as slow or biological sand filters, are passive systems that are used to remove contaminants from domestic wastewater, industrial wastewater and drinking water. This review focuses specifically on their application for remediation of industrial effluent and sewage-containing municipal and household effluent. The relationships between the physicochemical characteristics of the sand grains (size, size distribution, shape, chemical composition) and the hydraulic conductivity of the sand employed in BSFs are critically discussed in relationship to the achievable loading rates and hydraulic retention times. The modes of operation and influence of the functional microbial biomass as well as biodegradable and recalcitrant particulates on these parameters is comprehensively reviewed. Finally, the bioremediation of sewage-based and industrial wastewater is examined. This includes an account of the biotic and abiotic removal mechanisms and the limitations of BSRs for removal of pollutants such as phosphorus/phosphate and nitrates/nitrites. The removal mechanisms and removal efficiencies of macronutrients, micropollutants, fecal indicators and other microorganisms such as antibiotic-resistant bacteria in BSRs are discussed.

Operational characteristics in varied gradients of low carbon-to-nitrogen ratios utilizing a novel integrated bacteria-algae synergistic biofilm reactor for wastewater treatment

Evaluating a novel algal-bacterial biofilm integrated reactor (A-BBR) designed to reduce energy consumption and greenhouse gas emissions, wastewater treatment characteristics were simulated at low carbon-to‑nitrogen ratios. Pollutant removals were investigated under low organic loads at different carbon-to‑nitrogen ratios (ranging from 7.24 to 4.59). COD and NH4+-N removal rates surpassed 90 %, with TN removal exceeding 80 %, demonstrating a notable performance improvement over the fixed-bed biofilm reactor (FBBR). The efficient utilization of organic substrate during denitrification by the bacteria-algae symbiosis system resulted in an increase in nitrogen removal per unit concentration of organic matter. Tracking studies of photosynthetic oxygen production rate versus specific aerobic rate and chlorophyll in the reactor demonstrated that additional aeration was unnecessary during the photoreaction phase, reducing energy losses. The decrease in the carbon-to‑nitrogen ratio was positively correlated with the increase in facultative diatom species within the biofilm. As the carbon-to‑nitrogen ratio had decreased from 7.24 to 4.59, the content of diatoms had increased by over tenfold compared to the initial stage. Furthermore, as the diversity of algae species increased, the difference between the photosynthetic oxygen production rate and the specific aerobic rate had risen from 7.6 to 13.8. This indicated that the algal-bacterial biofilm system with a richer diversity of algae exhibited a higher photosynthetic oxygen production rate compared to the monoalgal system. These results furnish valuable insights for future inquiries into the utilization and underlying mechanisms of bacterial and algal biofilms in the context of water treatment.

Research of the process of biological wastewater treatment under conditions of uneven load of the treatment system

The main purpose of the article is to develop a multifactorial model for rapid assessment of the efficiency of biological wastewater treatment reactors. A mathematical model of the process of biological wastewater treatment has been developed based on: changes in the concentration of organic contaminants in the bioreactor over time, taking into account the uneven flow of wastewater to the treatment plant, the process of substrate entering the bioreactor (different amounts may enter at different times). The software implementation of the proposed algorithm for solving the corresponding model problem in Python is carried out. The results of computer experiments on the study of the efficiency of wastewater treatment in biological treatment reactors for different operating conditions of facilities are presented. In particular, such processes were considered with taking into account the unevenness of the load, because the maximum cleaning loads are in the morning and in the evening. The task was solved to simulate a real situation and show how cleaning takes place at the maximum load at a certain time of the day. The results obtained will be useful for calculations in the design of biological treatment facilities or in the reconstruction of existing bioreactors for their prospective operation under new operating conditions.

Performance of a Solar-Driven Photocatalytic Membrane Reactor for Municipal Wastewater Treatment

The increasing demand for efficient wastewater treatment technologies, driven by global population growth and industrialisation, highlights the necessity for advanced, reliable solutions. This study investigated the efficacy of a slurry photocatalytic membrane reactor (PMR) for the advanced removal of organic pollutants, quantified via chemical oxygen demand (COD), under natural and simulated solar light irradiation. Employing two variants of iron-doped titania as photocatalysts and a polysulfone-based polymeric membrane for the separation process, the investigation showcased COD removal efficiencies ranging from 66–85% under simulated solar light to 52–81% under natural sunlight over a 7 h irradiation period. The overall PMR system demonstrated COD removal efficiencies of 84–95%. The results confirmed the enhanced photocatalytic activity afforded by iron doping and establish solar-powered slurry PMRs as an effective, low-energy, and environmentally friendly alternative for the advanced treatment of municipal wastewater, with the research providing valuable insights into sustainable water management practices.

Utilization of native Chlorella strain in laboratory-scale raceway reactor for synthetic wastewater treatment: A study in batch and continuous modes with multi-substrate modeling

Despite of the possibility to include microalgae in civil wastewater treatment process, the practice is still not common due to the lack of available instruments to implement it. In this study, a straightforward comprehensive approach for dealing with microalgal wastewater treatment involving an original kinetic model is proposed. A first set of batch cultures of a native strain of Chlorella was firstly carried out to obtain the kinetic parameters: maximum growth factor (μmax) and half-saturation constant (Ks), for each limiting nutrient. Maximum growth factor values of 0.0279 for PO43−, 0.0319 h−1 for NH4+, 0.0352 h−1 for glucose, and 0.0263 h−1 for the overall medium were found. Regarding the Ks, values of 1.08 mg L−1, 27.70 mg L−1, 1.34 mg L−1, were found for PO43−, NH4+ and glucose respectively, and a value of 2.8 % of the total nutrients for the overall medium. These parameters were used to set a multi-substrate kinetic model able to predict the growth in batch and in continuous operation within a laboratory scale raceway reactor. The removal capabilities of the microalgae for each addressed pollutant were evaluated in a batch system and in a continuous system at dilution rates of 0.0025, 0.005, 0.01 and 0.015 h−1. This comprehensive approach represents a significant step towards addressing the continuous treatment of wastewater utilizing microalgae.

Superiority of basalt fibers with different modifications in contact oxidation reactor for wastewater treatment: Exploration of microbial community and underlying mechanism

Modified basalt fiber (MBF) has been employed as biological carrier to strengthen wastewater treatment. However, few studies focused on the superiority of different MBFs and their microbial mechanisms. In this study, after surface coating and chemical grafting, four MBFs and BF were applied as carriers in contact oxidation reactors. Surface roughness and area of MBFs increased in relation to original BF. Compared to BF group, MBFs could improve nutrients removal performance and stability, probably owing to impacts on microbial community structure. Specifically, calcium coating (Ca-MBF) contributed to the highest ammonium removal in average (72.25%), due to the relative more stimulation on Nitrosomonas and Nitrospira. Improvement on nitrification in Ca-MBF group resulted in the most significant increase of total nitrogen removal by 9.72% (p < 0.05) compared to BF. In contrast, chemical grafting was more inclined to enhance denitrification, particularly in PEI-MBF group, which was 34.62% higher (p < 0.05) than BF. The most enrichment on denitrification bacteria was also observed in PEI-MBF group (51.29%), including Zoogloea, Flavobacterium, and Acinetobacter, causing promotion on microbial denitrification. Besides, chemical grafting brought about more phosphate accumulating organisms like Thauera, Acinetobacter, and Pseudomonas, increasing total phosphorus removal compared to BF by 4.27–18.53%. Nevertheless, the highest phosphorus removal was discovered with Ca modification, inconsistent to the lowest microbial abundance, suggesting that more physical absorption sites by Ca modification was the major reason for enhancement on phosphorus removal. This work provided insights into application potential of different modified BFs for wastewater treatment.

Needle-Felt Coir fibre: A natural substitute for synthetic media in anaerobic fixed film reactors for wastewater treatment

In the past, studies have been conducted to evaluate different materials as filter media during anaerobic treatment of wastewater. The present study aims to assess the viability of using needle-felt coir fibre as a biofilm carrier in an anaerobic baffled reactor for organic-rich wastewater treatment. Real wastewater from a canteen with chemical oxygen demand (COD) - 1400±560 mg/L, and suspended solids (SS) - 397±23 mg/L after stabilization was treated for six months in a pilot scale unit with the carrier medium. The high porosity (90%) and specific surface area (1450±299 m2/m3) of the medium enabled COD (66%) and SS (70.5%) removal along with biogas recovery, at a lower hydraulic retention time of 14 hrs. The metagenomic sequence analysis revealed rich and diverse bacteria and methanogenic archaea in the carrier medium and settled sludge. Compared to the commonly used synthetic media, the needle-felt coir fibre carrier has technical, environmental, and economic advantages. Therefore, needle-felt coir fibre might be a sustainable replacement for conventional synthetic media in anaerobic wastewater treatment systems.

Nitrate increases the capacity of an aerobic moving-bed biofilm reactor (MBBR) for winery wastewater treatment.

We used bench-scale tests and mathematical modeling to explore chemical oxygen demand (COD) removal rates in a moving-bed biofilm reactor (MBBR) for winery wastewater treatment, using either urea or nitrate as a nitrogen source. With urea addition, the COD removal fluxes ranged from 34 to 45 gCOD/m2-d. However, when nitrate was added, fluxes increased up to 65 gCOD/m2-d, twice the amount reported for aerobic biofilms for winery wastewater treatment. A one-dimensional biofilm model, calibrated with data from respirometric tests, accurately captured the experimental results. Both experimental and modelling results suggest that nitrate significantly increased MBBR capacity by stimulating COD oxidation in the deeper, oxygen-limited regions of the biofilm. Our research suggests that the addition of nitrate, or other energetic and broadly used electron acceptors, may provide a cost-effective means of covering peak COD loads in biofilm processes for winery or another industrial wastewater treatment.

Feasibility of replacing proton exchange membranes with pressure-driven membranes in membrane electrochemical reactors for high salinity organic wastewater treatment

Membrane electrochemical reactor (MER) shows superiority to electrochemical oxidation (EO) in high salinity organic wastewater (HSOW) treatment, but requirement of proton exchange membranes (PEM) increases investment and maintenance cost. In this work, the feasibility of using low-cost pressure-driven membranes as the separation membrane in MER system was systematically investigated. Commonly used pressure-driven membranes, including loose membranes such as microfiltration (MF) and ultrafiltration (UF), as well as dense membranes like nanofiltration (NF) and reverse osmosis (RO), were employed in the study. When tested in a contamination-free solution, MF and UF exhibited superior electrochemical performance compared to PEM, with comparable pH regulation capabilities in the short term. When foulant (humic acid, Ca2+ and Mg2+) presented in the feed, UF saved the most energy (43 %) compared to PEM with similar removal rate of UV254 (∼85 %). In practical applications of MER for treating nanofiltration concentrate (NC) of landfill leachate, UF saved 27 % energy compared to PEM per cycle with the least Ca2+ and Mg2+ retention in membrane and none obvious organics permeation. For fouled RO and PEM with ion transport impediment, water splitting was exacerbated, which decreased the percentage of oxidation for organics. Overall, replacing of PEM with UF significantly reduce the costs associated with both the investment and operation of MER, which is expected to broaden the practical application for treating HSOW.

Enhancement of denitrification by sulfur-based carrier in sequencing batch reactor (SBR) for advanced wastewater treatment

This study was to enhance the nitrogen removal efficiency in the sequencing batch reactor (SBR) process by adding sulfur-based carriers. The nitrogen removal efficiency of the control group was compared with that of the experimental group through a two-series operation of SBR1 without carrier and SBR2 with the carrier under the condition of no external carbon source. A total nitrogen (T-N) removal efficiency of 6.6%, 72.6%, and 79.9% was observed in SBR1, SBR2 (5%), and (10%), respectively. The T-N removal efficiency was improved in the system with carriers, which showed an increase in the removal efficiency of approximately 91.7%. The results suggest that the inclusion of the carrier led to an elevation in the sulfur ratio, implying an augmented surface area for sulfur-based denitrifying microorganisms. Additionally, CaCO3 contributed essential alkalinity for sulfur denitrification, thereby preventing a decline in pH. Regardless of the carrier, the efficiency of organic matter removal surpassed 89%, indicating that the sulfur-based carrier did not adversely affect the biological reaction associated with organic matter. Therefore, autotrophic denitrification was successfully performed using a sulfur carrier in the SBR process without an external carbon source, improving the nitrogen removal efficiency.

Implications of natural coagulants and the development of a chemical coagulation reactor for dairy wastewater treatment with product recovery from waste sludge

Implications of natural coagulants and the development of a chemical coagulation reactor for dairy wastewater treatment with product recovery from waste sludge

Fe loading 3D micro-meso-porous carbon sphere derived from natural cellulose of sawdust activating peroxymonosulfate for degradation of enrofloxacin

Fe loading 3D micro-meso-porous carbon sphere (Fe@3C-2N) was derived from natural cellulose of sawdust and melamine through sodium alginate and ferric chloride cross-linking followed by carbonization processes, which served as peroxymonosulfate (PMS) activators for enrofloxacin (ENR) degradation. The cellulose was produced by the delignification of sawdust with sodium chlorite. The delignification of sawdust and the addition of melamine increased the porosity and electron transport capacity of Fe@3C-2N. When the dosages of Fe@3C-2N and PMS were 0.60 g L−1 and 0.20 g L−1 respectively, the degradation rate of ENR (20 mg L−1) reached 92.17 % within 80 min, suggesting the satisfactory activation performance of PMS. The good structural stability of Fe@3C-2N makes it suitable for use as packing in continuous flow reactors for wastewater treatment. Quenching experiments and electron paramagnetic resonance (EPR) suggested that SO4•− and 1O2 were the dominant reactive oxygen species (ROSs) in Fe@3C-2N/PMS system. X-ray photoelectron spectroscopy (XPS) revealed that Fe3C, pyrrolic N and graphitic N were the potential active sites.

Unveiling the hidden diversity and functional role of Chloroflexota in full-scale wastewater treatment plants through genome-centric analyses

Abstract The phylum Chloroflexota has been found to exhibit high abundance in the microbial communities from wastewater treatment plants (WWTPs) in both aerobic and anaerobic systems. However, its metabolic role has not been fully explored due to the lack of cultured isolates. To address this gap, we use publicly available metagenome datasets from both activated sludge (AS) and methanogenic (MET) full-scale wastewater treatment reactors to assembled genomes. Using this strategy, 264 dereplicated, medium- and high-quality metagenome-assembled genomes (MAGs) classified within Chloroflexota were obtained. Taxonomic classification revealed that AS and MET reactors harbored distinct Chloroflexota families. Nonetheless, the majority of the annotated MAGs (166 MAGs with &amp;gt;85% completeness and &amp;lt; 5% contamination) shared most of the metabolic potential features, including the ability to degrade simple sugars and complex polysaccharides, fatty acids and amino acids, as well as perform fermentation of different products. While Chloroflexota MAGs from MET reactors showed the potential for strict fermentation, MAGs from AS harbored the potential for facultatively aerobic metabolism. Metabolic reconstruction of Chloroflexota members from AS unveiled their versatile metabolism and suggested a primary role in hydrolysis, carbon removal and involvement in nitrogen cycling, thus establishing them as fundamental components of the ecosystem. Microbial reference genomes are essential resources for understanding the potential functional role of uncultured organisms in WWTPs. Our study provides a comprehensive genome catalog of Chloroflexota for future analyses aimed at elucidating their role in these ecosystems.

A review of modified and hybrid anaerobic baffled reactors for municipal wastewater treatment with a focus on emerging contaminants

This review discusses municipal wastewater treatment using anaerobic baffled reactors (ABRs) and modified ABRs to remove C, N, P and emerging contaminants.

Response of the nitrification sludge to oxytetracycline and operating the nitrifying reactor for oxytetracycline wastewater treatment

The nitrify-based technology has already been regarded as an economical and efficient strategy to remove nitrogen. This study investigated different oxytetracycline (OTC) concentrations inhibited the nitrifying process of an aerobic wastewater treatment system in short-term shocks. The stability of ammonia nitrogen removal had declined trend and demonstrated nitrite accumulation when the concentration of oxytetracycline was 0,1,2,5,10,20mg/L, respectively. And the ammonia oxidation reaction time decreased from 240 min to 120 min. Mixed liquid suspended solids (MLSS) decreased by 50.69%, 48.53%, 74.28%, 65.03%, and 72.97%, respectively. Compared to control OTC (0 mg/L), S-PN decreased from 2.256 mg·gVSS-1 to 0.016 mg·gVSS-1, 0.294 mg·gVSS-1, 0.094 mg·gVSS-1, 0.649 mg·gVSS-1, 0.349 mg·gVSS-1. Total EPS decreased from 7.795 mg·gVSS-1 by 17.00%, 32.91%, 45.09%, 43.04%, and 29.57%, respectively. High-throughput sequencing analyses showed that Proteobacteria and Bacteroidetes were the most phylum. The relative abundance of Nitrospira decreased as the OTC concentration increased, while that of Comamonas increased.