Artificial Aeration Research Articles

Performance comparison of different types of constructed wetlands for the removal of pharmaceuticals and their transformation products: a review.

This paper presents a comprehensive and critical comparison of four types of constructed wetlands (CWs): free water surface CW (FWSCW), vertical flow CW (VFCW), horizontal flow CW (HFCW), and hybrid CW (HCW) for the removal of 29 pharmaceuticals (PhCs) and 19 transformation products (TPs) using a global data compiled for 247 CWs reported in 63 peer-reviewed journal papers. Biodegradation (aerobic being more efficient than anaerobic) is the major removal mechanism for 16 out of 29 PhCs besides the influence of other processes (e.g., adsorption/sorption, plant uptake, and photodegradation). The HCW performed better followed by VFCW, HFCW, and FWSCW. The comparatively better removal in HCW might be due to the coexistence of aerobic and anaerobic conditions and longer hydraulic retention time considering more than one compartment enhances the removal of PhCs (e.g., diclofenac, acetaminophen, sulfamethoxazole, sulfapyridine, trimethoprim, and atenolol), which are removed under both conditions and adsorption/sorption processes. The augmentation in dissolved oxygen by the application of artificial aeration improved the removal of PhCs, which are degraded under aerobic conditions. Furthermore, the better performance of aerated CWs could be due to the establishment of various microenvironments with different physicochemical conditions (aerobic and anaerobic), which facilitated the contribution of both aerobic and anaerobic metabolic pathways in the removal of PhCs. The removal of some of the PhCs takes place by the formation of their TPs and the nature of these TPs (persistent or non-biodegradable/biodegradable) plays a major role in their removal process.

Artificial soil aeration increases soil bacterial diversity and tomato root performance under greenhouse conditions

AbstractSoil aeration can enhance soil enzyme activity and plant growth. These effects may be caused by variations in soil microbial diversity and plant root development. However, little is known about the responses of soil microbial composition, structure, and diversity and plant root development to artificial soil aeration. The aims of this study were to examine the composition, structure, and diversity of rhizosphere bacterial communities and tomato root morphology under four aeration volumes in combination with drip‐tubing placed at two different soil depths. The aeration volumes (V) were 0, 0.5, 1, and 1.5 times (CK, V1, V2, and V3, respectively) the standard aeration volume. The drip irrigation tube burial depths were 15 (D15) and 40 cm (D40). The results demonstrated that soil aeration had a significant influence on root performance (root morphology and activity) and soil bacterial diversity in the tomato root zone. In comparison with the CK treatment, V3 soil aeration increased root length, surface area, tip number, and activity by 7.9%, 6.3%, 14.5%, and 7.0%, respectively. The abundance‐based coverage estimator, Chao index, and Shannon diversity increased by 5.3%, 4.7%, and 3.5%, respectively. The abundance of Acidobacteria increased and that of Gammaproteobacteria decreased in response to the soil aeration treatments; conversely, Geobacteraceae and Halanaerobiaceae were eliminated. Moreover, different subsurface tubing placement depths changed the rhizosphere bacterial community. The results indicate that soil aeration ameliorates hypoxic conditions and provides benefits to soil bacterial communities and root morphology.

Prediction of dissolved oxygen in a fishery pond based on gated recurrent unit (GRU)

Dissolved oxygen (DO), an important water quality indicator in aquaculture, affects the survival rate of aquatic creatures and the yield of aquatic production. Therefore, it is important to predict DO in fishery ponds for applying artificial aeration with low energy and cost. Recently, deep learning models, such as recurrent neural network (RNN), long short-term memory (LSTM), and gated recurrent unit (GRU), are often used to predict the trend of time series, but it is unclear which one of them is more suitable for prediction of DO in fishery ponds. In this work, the RNN model, LSTM model, and GRU model were used to build three DO predicting models. The performance of the three models were compared by mean absolute error (MAE), mean square error (MSE), mean absolute percentage error (MAPE), and the coefficient of determination (R2). The performance of RNN is worse result than LSTM and GRU. The four evaluation indicators of GRU are 0.450 mg/L, 0.411, 0.054, and 0.994, and the four indicators of LSTM are 0.407 mg/L, 0.294, 0.059, and 0.970, which shows that the performance of GRU is similar to LSTM, but the time cost and number of parameters used for GRU is much lower than LSTM. It is concluded that the GRU has overall better performance and can be applied to practical applications.

Combining artificial aeration and biological zeolite mulch for nitrogen removal from eutrophic water bodies

Abstract Endogenous nitrogen pollution can be a major cause of eutrophication. Nitrogen species release from sediments can be reduced by biologically-enforced zeolite mulch or water column aeration. This study was about their combined effects. Water and surface sediment samples from the Yangzhou ancient canal were aerated and biozeolite mulching was applied separately and in combination for 81 days, while the nitrogen species removal rate was recorded. The combination of aeration and biozeolite mulching removed >95% of the ammoniacal-nitrogen in 15 days. This was better than either the blank control or biozeolite mulch without aeration. The ammoniacal-nitrogen concentration was lowered faster by combined treatment than by aeration alone. Nitrate nitrogen was only detected during aeration between days 10 and18, and reached lower concentration in the presence of biozeolite. Nitrate was formed during aeration but its concentrations were higher and more variable in the absence of biozeolite; that is, mulching stabilized nitrate formation. The total nitrogen concentration reached its lowest levels after 81 days with biozeolite treatment alone, with 78% total nitrogen removal, whereas combined aeration with biozeolite achieved 41%. This shows that biozeolite mulching can remove nitrogen in eutrophic waters, even without aeration.

Modeling sediment oxygen demand in a highly productive lake under various trophic scenarios.

Hypolimnetic oxygen depletion in lakes is a widespread problem and is mainly controlled by the sediment oxygen uptake (SOU) and flux of reduced substances out of the sediments (Fred). Especially in eutrophic lakes, Fred may constitute a major fraction of the areal hypolimnetic mineralization rate, but its size and source is often poorly understood. Using a diagenetic reaction-transport model supported by a large data set of sediment porewater concentrations, bulk sediment core data and lake monitoring data, the behavior of Fred was simulated in eutrophic Lake Baldegg. Transient boundary conditions for the gross sedimentation of total organic carbon and for hypolimnetic O2 concentrations were applied to simulate the eutrophication and re-oligotrophication history of the lake. According to the model, Fred is dominated by methanogenesis, where up to70% to the total CH4 is produced from sediments older than 20 years deposited during the time of permanent anoxia between 1890 and 1982. An implementation of simplified seasonal variations of the upper boundary conditions showed that their consideration is not necessary for the assessment of annual average fluxes in long-term simulations. Four lake management scenarios were then implemented to investigate the future development of Fred and SOU until 2050 under different boundary conditions. A comparison of three trophic scenarios showed that further reduction of the lake productivity to at least a mesotrophic state is required to significantly decrease Fred and SOU from the present state. Conversely, a termination of artificial aeration at the present trophic state would result in high rates of organic matter deposition and a long-term increase of Fred from the sediments of Lake Baldegg.

The effect of Yucca schidigera extract dietary supplementation on growth performance, feed and protein utilization of European seabass, Dicentrarchus labrax, fingerlings

A total of 180 apparent healthy European seabass, Dicentrarchus labrax, fingerlings (5.0±0.5 g fish-1) were used to investigate the effect of different levels of Yucca, Yucca schidigera, extract (YE) on growth performance, feed utilization and survival rate. Yucca extractwere used at level of 0, 0.25, 0.50 and 1 g YE kg-1 diet for 45 days. The fish were reared in twelve glass aquaria (three replicates per treatment), measuring (70x40x30 cm; approximately 70 liters each) at an initial stocking density of 15 fish aquarium-1. The aquaria were supported with artificial aeration and the water exchange rate was 15% with saline ground water (32‰). The results indicated that YE dietary supplementation significantly improved final weight, weight gain and specific growth rate in groups fed on 0.50 and 1 g YE kg-1 diet compared to the control. Feed intake tended to increase with all groups fed on YE supplemented diet. The feed conversion ratio and protein efficiency ratio improved significantly with the highest two level of YE compared to the control. From the above mentioned, it can be concluded that YE can be used at level of 1 g YE kg-1 diet as feed additive in sea bass fingerlings diet for improving growth performance and FCR and protein metabolism and maintaining survival rate.

The role of concentrations gradients on phosphorus and iron dynamics from chemically-dosed horizontal flow wetlands for tertiary sewage treatment.

This study examined the dynamics of iron (Fe) and phosphorus (P) transformations from the surface sludge accumulated in tertiary horizontal flow (HF) treatment wetlands (TW) chemically dosed for P removal. Site surveys showed P was stored in HF TW with and without artificial aeration on average, with instances of P release in the non-aerated site. Controlled experiments revealed storing TW surface sludge for over 24 hours resulted in limited oxygen and nitrate concentrations, resulting in both P and Fe release. The rate of P release increased with increasing water-sludge P concentration gradients, and the reaction could take as little as 10 minutes. Convection had no impact on P transformation rates. The findings suggest mitigation strategies could include the manipulation of the biogeochemical environment by managing oxygen and nitrate concentrations within the wetlands. A better understanding of links between Fe, P, and nitrate is needed to test proactive mitigation strategies for small wastewater treatment plants.

Artificial aeration of stepped spillways by crest piers and flares for the mitigation of cavitation damage

Stepped spillways are one of the oldest spillway designs dating back to 500 B.C. With technical advances in Roller Compacted Concrete (RCC) construction, the stepped spillway has become increasingly popular over recent decades. However, the use of this spillway is limited to a maximum safe unit discharge of 25 m2/s due to the risk of cavitation. In order to increase the discharge capacity on stepped spillways, various crest pier designs were introduced for flow aeration, thereby reducing the risk of cavitation damage. These pier designs were investigated on two physical models, constructed on a scale of 1:15 and 1:50, both with a standard ogee crest profile which transit to a stepped spillway chute. Air concentration was recorded along the pseudo-bottom, while pressures were measured at the step riser. The results of the 1:15 scale model indicated that the implementation of a short bullnose pier increased the safe unit discharge capacity to 30 rm/s. The innovative Flaring Gate Pier design, which was adapted on existing spillways in China, with reported design prototype unit discharges exceeding 200 m2/s, was investigated on the 1:50 scale model. Based on the experimental results of the current study, the safe unit discharge capacity (i.e. a discharge satisfying the relevant criteria defined for this study) was increased to 50 m2/s with an X-shape Flare Gate Pier (FGP) on the spillway crest.

Life cycle assessment and costing of wastewater treatment systems coupled to constructed wetlands

This study evaluates the environmental and economic performance (ecoefficiency) of two decentralized, small-scale, wastewater treatment systems coupled to constructed wetlands. System One comprises a vertical and a horizontal flow wetland. System Two comprises a vertical subsurface flow wetland with artificial aeration. A life cycle assessment based on data from two actual pilot structures was carried out. The functional unit was 1 m3 of treated water over a 20-year long lifetime. The systems were modeled in open LCA software, with the aid of Ecoinvent 3.3 data, and the impact assessment was based on the ReCIPe method. Results have demonstrated that foreground emissions such as direct greenhouse gas released from the septic tank and nutrients released in the effluent have driven potential impacts related to Climate Change, Photochemical Oxidants, and Freshwater Eutrophication. Artificial aeration reduces the area required for the installation of the system and electricity consumption was responsible for only 7% of total Climate Change related potential impact. Technologies that reduce direct (foreground) liquid and airborne emissions will improve the environmental performance of the systems. The analysis of the aerated wetland has shown that the operation stage had the greatest environmental impact potential for all analyzed impact categories, with results varying between 64% for Human Toxicity and 100% for Freshwater Eutrophication. The life cycle cost per cubic meter of treated sewage for the aerated system was 1.8 times smaller than that of the system without aeration. Thus, aeration is cost-effective for small-scale wastewater treatment systems coupled to constructed wetlands.

Effect of combined stress (salinity + hypoxia) and auxin rooting hormone addition on morphology and growth traits in six Salix spp. clones

Willows plantations development could be an alternative for hydro-halomorphic soils but it is limited by combined stress salinity + hypoxia (main stressor under waterlogging conditions). We studied the effects of saline stress, alone or interacting with hypoxia, on growth, morphology and rooting process of six willows clones, assessing also whether rooting hormone (H, Indol Butyric Acid) contributes enhancing rooting under combined stress. Three hybrids of Salix matsudana × Salix alba (Sm×Sa), two of Salix babylonica × Salix alba (Sb×Sa) and a Salix nigra (Sn4) clone were evaluated in hydroponics. Ten treatments were generated combining salinity [moderate (MS): 5 dS/m, and high (HS): 10 dS/m]; hypoxia (with or without artificial aeration, HypO), and presence or absence of H. After 120 days, shoot and root biomass, root number and length, and hypertrophied lenticel number were evaluated. Contrary to what was expected, Sm×Sa and Sb×Sa hybrids showed no adverse additive effects of combined stress compared with saline stress; whereas in Sn4, S + HypO favored root biomass production increasing number and elongation of roots. Salinity was the main limiting factor for root production, being only MS conditions compatible with rooting, although limited. There was no common response in relation to H addition. In Sn4, H potentiated the effects of MS + HypO on root biomass, increasing number of roots. However, it had no positive effect on biomass production in the remaining hybrids, producing a higher root number but shorter in length. More effort is needed to understand the physiological mechanisms behind the response to combined stress in willows.

Enhanced nitrogen removal by the integrated constructed wetlands with artificial aeration

Abstract The removal of organic pollutants, ammonia, and phosphorus from seriously polluted river water has been extensively explored using various traditional integrated constructed wetland systems. However, the removal efficiency of nitrogen was extremely low due to the limited oxygen concentration of these traditional systems. Herein, a novel pilot-scale integrated constructed wetland system (CWs), which consisted mainly of a biotic contacting oxidization pre-treatment (BCO), an artificial aeration vertical sub-surface flow CWs, and a horizontal subsurface flow CWs were applied to enhance the removal of total nitrogen (TN) under high hydraulic loading through artificial aeration. Results showed that, with the application of the novel CW systems, a total of 64.97% removal of TN was achieved with the average inflow of 11.39 mg/L and hydraulic load of 1.67 m3 ⋅ m−2 ⋅ d−1. Further analysis showed that the contributions of BCO, AVFCWs and HF CWs to TN removal were 13.86%, 15.97% and 35.36%, respectively. Besides the TN removal, the CW systems can also obtained about 75% of ammonia removal, within which artificial aeration vertical subsurface flow CWs unit occupied about 60% of contribution. Flowing by the application of this systems, the concentrations of ammonia and nitrate in the outflow decreased to 2.66 and 2.01 mg/L, respectively. The study indicated that the integrated constructed wetland system applied can be an efficiently potential technique for the removal of COD, NH4-N and TP from some rural wastewater.

From Saprotrophic to Clear Water Status: the Restoration Path of a Degraded Urban Lake

The study was conducted on Długie Lake in Olsztyn, which for 20 years since the mid-1950s served as a domestic and storm wastewater receiver, which led to its complete degradation. The discontinuation of wastewater inflow in 1976 caused a change in the trophic state from saprotrophic to hypertrophic. Evident improvement of water quality was possible only after the implementation of proper restoration techniques. Długie Lake was subjected to artificial aeration with thermal destratification (1987–2000). After all opportunities to improve water quality in the lake by artificial aeration (low phosphorus sorption capacity of sediment) had been exhausted, it was decided that a phosphorus inactivation method using the coagulant PAX 18 be used (2001–2003). Before restoration, the nutrient concentration in the near-bottom water layer of Długie Lake was very high at 22.9 mg TN L−1 and 3.50 mg TP L−1. The average amount of chlorophyll a was ca. 200 μg L−1, and the Secchi disc visibility did not exceed 1 m. In 2017, 14 years after termination of the lake restoration process, the total phosphorus concentration at the bottom was 0.21 mg P L−1 on average, and the total nitrogen was 1.5 mg N L−1. The mean transparency of the water oscillated around approximately 5 m, and the amount of chlorophyll a was 1.86 μg L−1. Studies have shown that the most important step in reclamation is to prevent pollutants from entering the lake to the maximum extent possible and to use a combination of several reclamation methods as a matter of good practice. Stable environmental conditions have developed in the lake, and the values of chlorophyll a and the Secchi disk visibility indicate that the lake has reached a mesotrophic state.

Fate and removal of antibiotics and antibiotic resistance genes in hybrid constructed wetlands

Hybrid design and artificial aeration has been widely applied in wetlands, but little is known about their effectiveness in the removal of antibiotics and antibiotic resistance genes (ARGs). Here we investigated the performance of various mesocosm-scale constructed wetlands (CWs) with artificial aeration and hybrid design in removal of antibiotics and ARGs from antibiotics-spiked domestic sewage. Four hybrid constructed wetland systems with zeolite as substrate and Iris tectorum Maxim as plant were set up to have different artificial aeration designs. The aqueous removal efficiencies of total antibiotics ranged from 87.4% to 95.3%, while those of total ARGs varied from 87.8% to 99.1%. The mass removal of antibiotics by the CWs was attributed mainly to the microbial degradation. The present study imply that sorption of substrates and biological processes could be the two main mechanisms for ARGs elimination. The results from this study showed the hybrid CWs with artificial aeration could enhance treatment efficiencies of antibiotics and ARGs as well as conventional pollutants.

Constructed wetland microcosms as sustainable technology for domestic wastewater treatment: an overview.

Constructed wetland microcosms (CWMs) are artificially designed ecosystem which utilizes both complex and ordinary interactions between supporting media, macrophytes, and microorganisms to treat almost all types of wastewater. CWMs are considered as green and sustainable techniques which require lower energy input, less operational and maintenance cost and provide critical ecological benefits such as wildlife habitat, aquaculture, groundwater recharge, flood control, recreational uses, and add aesthetic value. They are good alternatives to conventional treatment systems particularly for smaller communities as well as distant and decentralized locations. The pH, dissolved oxygen (DO), and temperature are the key controlling factors while several other parameters such as hydraulic loading rates (HLR), hydraulic retention time (HRT), diversity of macrophytes, supporting media, and water depth are critical to achieving better performance. From the literature survey, it is evaluated that the removal performance of CWMs can be improved significantly through recirculation of effluent and artificial aeration (intermittent). This review paper presents an assessment of CWMs as a sustainable option for treatment of wastewater nutrients, organics, and heavy metals from domestic wastewater. Initially, a concise note on the CWMs and their components are presented, followed by a description of treatment mechanisms, major constituents involved in the treatment process, and overall efficiency. Finally, the effects of ecological factors and challenges for their long-term operations are highlighted.

Physico-chemical and biological aspects of a serially connected lab-scale constructed wetland-stabilization tank-GAC slow sand filtration system during removal of selected PPCPs

A serially connected lab-scale Greater duckweed constructed wetland (CW)-stabilization tank (ST)-GAC sandwich slow sand filtration system was tested to remove four widely detected pharmaceuticals and personal care products (PPCPs) from natural water with a spiked concentration of 25 μg/L. High removals were achieved rapidly (93.5–100%), being on average 95.9%, 99.1%, 98.1% and 97.4% for DEET, paracetamol, caffeine and triclosan (n = 3), respectively. Except for DEET, no significant difference was observed between overall removals with and without artificial aeration in CW tank (p > 0.05), showing good stability of the system. COD was considerably removed under aeration and final TOC removal was 64.7%. Nitrite, nitrate, ammonia and phosphate were not detected at the end of the test (day 26). The microbial community structure in three connected units of the tested system showed differences and good stability after the aerators were removed. Proteobacteria was the most dominant phylum among the 47 phyla found. Microbes attaching to the Greater duckweed contributed more to the microbial community structure in CW and ST tanks than original natural water. However, at the end of the run, the structural differences among three units decreased. After aeration stopped, phylum composition became more stable in ST tank while CW tank showed small structural variation throughout the test. Various correlations were found between detected phyla, among which Proteobacteria and Bacteroidetes showed a significant negative correlation (R = −0.73, p < 0.001, FDR corrected). Good removal of target PPCPs and stability of the system show the potential application of this combined treatment process.

Improvement in the Hydrochemical Regime of Small Urban Water Bodies under Conditions of Artificial Aeration (on the Example of Lake Telbin)

Improvement in the Hydrochemical Regime of Small Urban Water Bodies under Conditions of Artificial Aeration (on the Example of Lake Telbin)

Oxygen Regime Control in Water Body Amelioration

An important aspect of water body amelioration is the control of the oxygen regime in water mass. Pollution of water bodies deteriorates their oxygen regime, and the natural inflow of oxygen through the free surface is not enough to compensate for oxygen consumption for pollutant oxidation. Water pollution by various substances causes damage resulting from a decrease in the ecological safety of urban water bodies. Data of World Health Organization (WHO) show that the contact of the population with polluted water bodies causes spreading of deceases, such as cholera, diarrhea, dysentery, hepatitis A, typhoid, and poliomyelitis, and creates considerable health risks.In this context, the artificial aeration of water mass with the use of aeration systems, which improve water quality, is gaining in importance. Most widespread among such aeration systems are diffused-air aerators, in which air supplied by a compressor passes through perforated diffuser plates. The size of the perforation is often chosen with no appropriate hydraulic substantiation. The size of the resulting air bubbles, no doubt, depends on the size of perforation holes; however, the available design relationships give contradictory results depending on the immersion depth of the diffuser plate and the working pressure, which determines air discharge velocity from diffuser plate perforations. This shows that the studies along this line are of scientific and practical importance.This article presents the analysis of the existing relationships for determining the size of air bubbles that form when air is pumped into water through nozzles of different diameters at different pumping rates; the analysis has shown the results of such calculations to differ considerably. Buckingham π-theorem was used to construct dimensionless groups, determining the relationship between the size of bubbles and the factors that govern the outflow of air into water. Dimensionless groups were used to obtain a formula for calculating the size of air bubbles at the aeration of water mass.

Effects of Temperature on the Embryonic Development of Octopus vulgaris

The effect of two temperatures (14°C and 18°C) and incubation systems (artificial versus female care) on the embryonic development of Octopus vulgaris was studied. Octopuses (six females and two males) were captured in the Ria of Vigo (Northwest Spain). Egg batches were divided into two groups: one left with female care, and others were incubated with artificial aeration. The results indicate that the type of incubation did not affect the embryonic development, whereas temperature had a marked effect on it. The duration of embryonic development was 40 days at 18°C and 67 days at 14°C. Results suggest that a reduction of around 24 days °C–1 can be obtained when O. vulgaris embryos are incubated into the temperature tolerance range of this species. Results showed that temperature modulated in a different form the embryonic development, at least until stage XIII, where embryos at 18°C showed lower values of eggs and embryo length than embryos at 14°C. The proportion of arm/total length was 21% higher in embryos at 14°C compared with 18°C, suggesting that in the first phases of embryo development, muscle development is favored at low temperature. Results showed that embryos at 14°C and 18°C had no differences in two critical processes, that is, nervous system synthesis (measured through eye synthesis) and organogenesis (measured through mantle length). The fact that there were no differences between hatchlings developing from embryos at both experimental temperatures demonstrates that O. vulgaris embryos can be favored if spawn occurs at relatively low temperatures.

INFECÇÃO POR Kudoa sp. NA MUSCULATURA ESQUELÉTICA DE Genyatremus luteus Blochii,1795 (PERCIFORME: HAEMULIDAE), PEIXE AMAZÔNICO

Os mixosporídios são parasitos celulares encontrados nos diversos órgãos dos peixes de água doce ou estuarinos. Este grupo é economicamente importante por ser causador de doenças em inúmeros peixes, incluindo aqueles de valor comercial. Kudoa é destaque neste grupo por causar mioliquefação pós-mortem no pescado tornando-os impróprios para o consumo humano e, por isso, o conhecimento acerca deste gênero é de extrema importância. O objetivo deste trabalho foi descrever e caracterizar morfologicamente ogênero Kudoa Meglitsch, 1947 encontrado na musculatura esquelética em Genyatremus luteus. Foram coletados 22 espécimes de Genyatremus luteus, no município de São Caetano de Odivelas, nordeste paraense. Após a captura, os animais foram acondicionados em sacos plásticos com aeração artificial e transportados vivos ao Laboratório de Pesquisa Carlos Azevedo (LPCA), na Universidade Federal Rural da Amazônia, onde foram mantidos em aquários. Os animais foram anestesiados, sacrificados e, posteriormente, necropsiados para avaliação em microscopia de luz (ML). Fragmentos de musculatura esquelética foram retirados e esporos isolados, tetracapsulados, com corpo quadrangular ou pseudoquadrangular, determinantes do gênero Kudoa foram encontrados. Estes fragmentos contendo parasitos foram colhidos e fixados, desidratados, diafanizados e impregnados em parafina liquida. Foi realizado corte histológico e coloração em H&amp;E, permitindo evidenciar a formação cística no interior e entre as fibras musculares. Estudos complementares estão sendo realizados para identificação da espécie encontrada, a fim de aumentar o conhecimento sobre o estado de sanidade dos peixes da região Amazônica no estado do Pará. PALAVRAS-CHAVE: Genyatremus luteus, Mioliquefação pós-mortem, Myxozoa.

Optimizing the performance of organics and nutrient removal in constructed wetland–microbial fuel cell systems

No studies have reported the operation optimization of constructed wetland–microbial fuel cell (CW–MFC) systems in terms of pollutant removal under the influence of multiple factors. Multifactor orthogonal experiment (L25(55)) was designed in this study to investigate the influence of multiple factors on the CW–MFC performance and determine the optimal operating conditions for the organics and nutrient removal. The tested factors include volume ratio of granular graphite in the substrates (A), dissolved oxygen (DO) concentration in the cathode zone (B), hydraulic retention time (HRT) (C), effluent reflux ratio (D), and external resistance (E). The results showed that the sequence and degree of the influence of the tested factors were C** > B** > E** > D* > A for chemical oxygen demand (CODCr) removal, C** > B** > D* > E > A for ammonia nitrogen (NH3-N) removal, C** > D** > B** > E* > A* for total nitrogen (TN) removal, and C** > D* > B > A > E for total phosphorus (TP) removal (* denotes significant influence (0.01 < p < 0.05) and ** denotes extremely significant influence (p ≤ 0.01)). HRT was found to be the most influential factor for pollutant removal in CW–MFCs with a contribution of over 50% for CODCr, NH3-N and TP removal, and over 45% for TN removal. The optimal operating conditions for CODCr, NH3-N, TN and TP removal in CW–MFCs were quite different from each other. Comprehensively considering the treatment efficiency of pollutant, treatment capacity of wastewater, and energy consumption from artificial aeration, the selected comprehensive optimal operating conditions for CW–MFCs were A = 20%, B = 1.5 mg/L, C = 1.5 days, D = 50%, and E ≤ 250 Ω. Moreover, incorporating the MFC significantly enhanced the organics and nitrogen removal in CWs by 8.72–11.04% CODCr and 9.78–12.04% TN.