Effect Of Aeration Research Articles

Effects of aeration on water quality in agricultural reservoirs in the northern Great Plains

Lerminiaux J, Norton B, Wilson RJ, Rimas R, Lavender TM, Finlay K. 2024. Effects of aeration on water quality in agricultural reservoirs in the northern Great Plains. Lake Reserv Manage. 40:264–284. Aeration of agricultural reservoirs is an encouraged practice in the northern Great Plains of Canada as it can improve water quality by reducing pathogenic bacteria and algal abundance. Cattle also prefer aerated water, resulting in greater weight gain. Despite its known benefits, agricultural reservoir aeration is still not uniformly adopted, largely given its cost of installation and maintenance. Wind powered aeration has been shown to be an eco-friendly and sustainable way to increase oxygen levels in agricultural reservoirs, but the mechanisms by which this aeration can improve water quality are not well documented. By comparing 5 aerated agricultural reservoirs to 5 unaerated agricultural reservoirs, we evaluated whether wind-powered aeration improves water quality. We measured dissolved oxygen, nitrogen, and phosphorus, algal biomass (as chlorophyll a), cyanobacteria abundance, and algal toxins (microcystin, anatoxin-a, and β-N-methylamino-L-alanine) in the aerated and unaerated agricultural reservoirs on a weekly basis over a 12-week period from mid June through August 2022. We found that the aerators were able to mix the water column and add oxygen to deeper regions of the agricultural reservoir, but this did not result in consistent improvements to any measured water quality parameter. The observed lack of a strong response to aeration suggests that this practice may provide only minimal water quality benefits, but aeration may still prove beneficial for deep (>2 m) and sheltered agricultural reservoirs that do not regularly mix from wind effects alone.

Organic Pollutants Removal in a Hybrid Constructed Wetland Wastewater Treatment Plant with an Aeration System

This study presents the efficiency of TSS and organic pollutants (BOD5 and COD) removal in a hybrid constructed wetland wastewater treatment plant (VF-HF type) with an aeration system. This study was conducted over 6 years (2017–2022) in a facility with a capacity of 4.5 m3/day located in southeastern Poland and designed to treat real domestic wastewater from a school building. The studied facility consists of a three-chambered septic tank, a pumping station with an aeration system, and two beds with vertical and horizontal flow planted with giant miscanthus and willow. As a result of artificial aeration, the dissolved oxygen concentration in wastewater after mechanical treatment increased significantly, by an average of 1.18 mg O2/L, and was negatively correlated with wastewater temperature. The cumulative pollutant removal effects of the treatment plant (primary settling tank + VFCW + HFCW) were 81% for TSS, 98% for BOD5, and 89% for COD. There was no statistically significant effect of aeration on the organic pollutant removal effects in the VF bed, and such an effect was found for the temperature of wastewater entering the VF bed. The TSS, BOD5, and COD removal effects in the VF bed and BOD5 in the VF-HF system were positively correlated with air temperature. The technological reliability of the treatment plant was 98% for TSS and 100% for BOD5 and COD. The use of artificial aeration of wastewater makes it possible to achieve high organic pollutant removal efficiency in SSF CWs and to compensate for limitations due to the reduction in the area of constructed wetland beds.

Influence of toilet flushing water when using an on-site faecal sludge treatment combining electrocoagulation-flotation and anaerobic digestion

Addressing the need for sustainable sanitation in public transport and tourism, this study evaluates electrocoagulation-flotation (ECF) combined with anaerobic digestion (AD) for treating synthetic human faecal sludge (FS). Especially the effects of influent aeration and the use of either rainwater or tap water for flushing on the efficiency of pollutant removal and methane production were investigated. In detail, flushing with rainwater combined with influent aeration resulted in the highest removal efficiency of total COD (tCOD), non-soluble COD (nsCOD), total nitrogen (TN), and total phosphate (TP) of 55 %, 27 %, 22 %, and 75 %, respectively, during ECF treatment, compared to 48 %, 15 %, 14 %, and 63 %, respectively, when tap water was used. As such, post-treatment is mainly necessary for the removal of TN. Combining flushing with rainwater and influent aeration also resulted in the highest faradeic efficiency (107 %) and the most insoluble iron coagulant formation. In contrast, the application of influent aeration during ECF of FS produced using rainwater flushing led to a decrease in methane production from 354 mL/g VS (when no aeration is applied) to 281 mL/g VS during subsequent AD. In conclusion, this study demonstrates that ECF can be applied as a good pre-treatment for sanitation water due to the high nsCOD and TP removal, by which ECF could replace, e.g., a septic tank. Furthermore, the potential of combining ECF with AD is demonstrated in view of energy recovery.

Looking deeper into the effects of scouring and aeration on membrane aerated biofilms: Analysis of nitrogen conversion, oxygen profiles and nitrous oxide emissions

This study investigated the effects of aeration and scouring strategies on the performance of Membrane Aerated Biofilm Reactors (MABRs) and the distribution of oxygen and nitrous oxide in the biofilm. Four flat sheet MABRs were operated with synthetic feed under different conditions: two with intermittent aeration (iMABR) and two with continuous aeration (cMABR). Scouring was induced by bubbling dinitrogen gas through the reactor bulk at low and high frequencies (LF and HF). In the iMABRs, a partial nitritation biofilm initially developed, but the biofilm adapted to the aeration strategy over time and became nitrifying. The cMABRs directly developed a nitrifying biofilm without a significant phase of partial nitritation. Limiting oxygen availability improved the overall performance with regards to total nitrogen (TN) removal by providing a better environment for anaerobic ammonium oxidation (Anammox) while limiting complete nitrification.Oxygen profiles were measured in the iMABR over time at different biofilms depths, showing that intermittent aeration led to various oxygen concentrations and temporal variations in the oxygen availabilities at different depths of the biofilm. Also, N2O emissions from the MABRs differed greatly between the different systems, but still remained lower compared to other reactor configurations for nitrogen removal, making the MABR technology a worthy alternative. The results showed large differences between the operating strategies of the MABRs and can help to gain more insight into the specific properties of MABRs for nitrogen removal.

Effect of Aeration and External Carbon Source on Nitrogen Removal and Distribution Patterns of Related-Microorganisms in Horizontal Subsurface Flow Constructed Wetlands

Nitrogen pollution of surface water is still a critical issue worldwide. In this study, a total of four treatments were conducted in horizontal subsurface flow constructed wetlands (HSSFCWs) to explore the removal rate of nitrogen in the carbon-deficient wastewater, including combination of aeration and external carbon source (CW_CA), external carbon source (CW_C), aeration (CW_A), and control group without aeration and carbon source (CW_CK). Results showed that the removal rates of total nitrogen (TN) in the enhanced treatments were increased compared with CW_CK. The highest removal rates of COD (66.56%), NH4+-N (73.51%), NO3−-N (79.31%), and TN (76.19%) were observed in the CW_CA treatment. The bacterial community structure at the fore and rear ends of HSSFCWs was simultaneously changed in the CW_CA and CW_C treatments, respectively. The highest richness index at both the fore and rear ends of HSSFCWs was found in the CW_CA treatment. The richness and diversity indices of CW_C declined at the fore ends of HSSFCWs, but increased at the rear ends of HSSFCWs. Furthermore, the functional bacteria and genes significantly changed among different treatments. At the fore ends of HSSFCWs, the highest relative abundance of nitrifiers and absolute abundance of amoA and nxrA were obtained in CW_A, and the highest relative abundance of denitrifying bacteria and absolute abundance of nirS, nirK, nosZ were found in CW_C. However, at the rear ends of HSSFCWs, the highest relative abundance of nitrifiers and denitrifying bacteria as well as the absolute abundance of related genes were also observed in the CW_CA treatment. Overall, CW_CA improved the nitrogen removal rate by increasing the abundance of nitrogen-converting functional microbes and the genes associated with nitrification and denitrification.

Effects of Nitrogen Input and Aeration on Greenhouse Gas Emissions and Pollutants in Agricultural Drainage Ditches

Understanding the patterns of greenhouse gas emissions and the changes in pollution load in terrestrial freshwater systems is crucial for accurately assessing the global carbon cycle and overall greenhouse gas emissions. However, current research often focuses on wetlands and rivers, with few studies on agricultural drainage ditches, which are an important part of the agricultural ecosystem. Investigating the greenhouse gas emission patterns and pollution load changes in agricultural drainage ditches can help accurately assess the greenhouse effect of agricultural systems and improve fertilization measures in farmlands. This study explored the effects of nitrogen input and aeration on the pollution load and greenhouse gas emission processes in paddy field drainage ditches. The results showed that aeration significantly reduced the concentration of ammonium nitrogen (NH4+) in the water, decreased the emissions of nitrous oxide (N2O) and methane (CH4), and slightly increased the emission of carbon dioxide (CO2), resulting in an overall reduction of the global warming potential (GWP) by 34.02%. Nitrogen input significantly increased the concentration of ammonium nitrogen in the water, slightly reduced the emissions of N2O and CH4, and increased the CO2 emissions by 46.60%, thereby increasing the GWP by 15.24%. The drainage ditches reduced the pollution load in both the water and sediment, with the overall GWP downstream being 9.34% lower than upstream.

Changes in chemical fractionation of copper and zinc in soil as a function of incubation moisture content and organic matter amendments

Copper and zinc are essential micronutrients that are potentially toxic when present in excess in soils. Their bioavailability depends on their speciation in soil, but this may vary with environmental conditions. Aeration and hence redox conditions, and organic matter amendments are among the factors likely to cause variation on metal fractionation. We have monitored the chemical fractionation of both native and added copper and zinc in a clay loam top soil during a 5-month laboratory incubation. The effects of aeration (moist soil or flooded) and addition of two organic matter amendments, alfalfa straw or leaf compost, were studied. Metal spike was more labile than legacy metal, and was slowly redistributed over the incubation period. Organic matter caused short-lived flushes of metals, attributed to metal chelation with soluble organic matter. This effect was greater for straw than for more stable compost. There was no evidence that added organic matter increased the capacity of soil organic matter to immobilise metal. Flooding solubilized soil metal (hydr)oxides, releasing legacy Cu and Zn, but with less effect on the capacity to immobilise metal spike. Effects of flooding and organic matter addition were not additive. Both metals appear to be precipitated as sulphides under reducing conditions, and accounted for in the acid soluble phase. Monitoring the dynamics of metal distribution gives a more comprehensive understanding of underlying processes than would a single measurement, and is closer to in campo conditions than slurry microcosms.

Effect of pure oxygen aeration on soluble microbial products production in activated sludge system under the toxic condition of phenol

Soluble microbial products (SMP) contribute most of effluent organic matter (EfOM) in biological treatment processes. These products cause membrane fouling and generate disinfection by-products. This study investigated the effect of pure oxygen aeration on the production and characteristics of SMP under the toxic condition of phenol. Two sequencing batch reactors with pure oxygen (O-SBR) and air (A-SBR) aeration were used in the experiments. Results showed that the effluent chemical oxygen demand values of O- and A-SBR were 36.11 ± 1.54 and 42.44 ± 1.42 mg/L, respectively. SMP was the dominant component of EfOM. The various aeration types caused differences in the contents of extracellular polymeric substances (EPS) and SMP in the two SBRs. The content of loosely bound EPS (LB-EPS) in A-SBR was higher than that in O-SBR by 25%, whereas the tightly bound EPS content in A-SBR was lower than that in O-SBR by 19%. Pure oxygen aeration decreased 15% of humic acids, 42% of polysaccharides, and 29% of protein contents of SMP compared with air aeration, but it did not change the functional groups of SMP. SMP concentration was positively correlated with LB-EPS. Pure oxygen aeration caused the low contents of LB-EPS and SMP. This study showed the effect of pure oxygen aeration on SMP reduction, which can be useful for toxic industrial-wastewater biological treatment.

Különböző gyepkezelések hatásának cönológiai és természetvédelmi vizsgálati eredményei üde gyepen

In grassland management systems, the various agrotechnical elements have to be used in many cases on "primitive grasslands", where the coordination of agricultural and nature conservation tasks is necessary. Here, animal husbandry is the main aspect, which includes the long-term preservation of the quality of the pasture, as well as the most economical use of the pasture and keeping the animals as cheap as possible. The tests were carried out on a grassy area on the border of the settlement of Aba. We examined the vegetation of 8 plots of the same size in the area and the quantitative and qualitative composition of the biomass produced there. In this thesis, we provide data on the vegetation composition and evaluation of the following treatments. The plots and treatments were as follows: I. plot-ventilated; II. parcel-relaxed; III. plot loosened and ventilated; ARC. parcel control; V. plot-ventilated and 15 t/ha manure; VI. plot loosened and 15 t/ha manure; VII. plot loosened, ventilated and 15 t/ha manure; VIII. plot loosened, ventilated and 30 t/ha manure. In each plot, 5 ceenological recordings were made using 4 x 4 m quadrats. The estimated coverage of each species was given in %, taking into account the proportion of grasslands and other species. Among Borhidi's plant ecological indicators, the species were evaluated based on the NB (relative values of nitrogen demand) and WB (relative soil water and soil moisture indicator numbers). The social behavior types (SZMT) were also defined based on Borhidi's work, and the nature conservation value categories (TVK) were defined according to Simon. The lifestyle analysis was performed based on Pignatti's lifestyle types. Based on the data, the composition of the vegetation of each plot changed significantly compared to the data of the control plot IV. A direct proportionality can be discovered between the increase in the cover value of the dominant lawn grasses, primarily Festuca arundinacea, Dactylis glomerata, Alopecurus pratensis, and Fabaeceae species (e.g. Lathyrus tuberosus, Lotus corniculatus) and the amount of applied nutrients. Based on the coenological survey of the eight examined areas, the control area (IV.) showed the most natural state, which was confirmed by the species composition and number of species. The IV. plots are close to I., II. and III. for plot recordings, which proves that aeration and loosening do not worsen the condition of the lawn, but rather promote the preservation of its natural state. The VII-VIII. plots have the smallest number of species, but based on the life form spectrum, naturalness indicators, nature conservation value categories and social behavior types, they are not very disturbed habitats. No significant difference can be detected between the effect of lawn loosening and lawn aeration, but III. plot, where both treatments were carried out, was closer to the control area. Regarding the effect of the lawn management methods, it was possible to produce a starting data set in the long term (with the same environmental conditions). Overall, the study gave valuable results regarding the age of change occurring during the application of different lawn management methods, and was also effective from an economic point of view.

Observation of Excess Air Discharge in the Budikdamber Pond Aeration System on the Real Effect of Tilapia Fish Health (Oreochromis spp.)

DO levels are needed by fish organisms for metabolic processes, so the value changes quickly. So, giving aeration all the time and siphonization every day is the best treatment in maintaining water quality for growth. However, a study revealed that there is a negative side to excessive aeration until it reaches a saturation point. The results of the study on the process and level of exposure related to gas bubble disease caused by hyperoxia. The first symptom is the presence of gas bubbles under the skin, gas bubbles appear on most of the fins, along the lateral line, gills and in the eyes. Currently, another research is being conducted to prove the real effect of excess aeration, specifically on the health of Tilapia in closed ponds at normal ambient temperatures. In the closed water pond system, air flow is given at 25 mg/L (first pool), 40 mg/L (second pool), and 54 mg/L (third pool), with variable treatment of feed, water quality (temperature & pH). , and the same volume. The focus of the type of fish that will be observed in this research is Tilapia, with a duration of observation for ± 1 month. The maximum DO measurement results at a normal ambient temperature of 25.6 °C pool water is 8.2 mg/L. The optimum DO level in the first pond that is aerated with an air flow of 25 L/m is ± 7.9 mg/L, the optimum DO level in an aerated pond with an air flow of 40 L/m is ± 8.1 mg/L, and the optimum DO level in an aerated pond with an air flow rate of 54 L/m is ± 8.1 mg/L. No matter how big the air flow from the aerator is put into the water, the DO level will not exceed the value of 8.2 mg/L as long as the water temperature is not lower than 25 °C. Tilapia in ponds containing the highest DO levels at normal ambient temperature conditions of this pond water (24.4 – 25.9 °C), grows and develops very well, in fact there is no adverse effect on health.

Effect of hydrodynamic aeration on bioelectricity generation from photoautotrophic Spirulina platensis in biophotovoltaic devices

A biophotovoltaic (BPV) device is a type of bioelectrochemical cell that shows potential for renewable energy production using photosynthetic exoelectrogenic microorganisms. However, the technology currently has limitations due to its relatively low power output and high dependence on biofilm attachment. Thus, this paper examines the effect of hydrodynamic aeration on the bioelectricity generation of BPV devices. Aeration is widely applied in microalgae cultivation to improve the mixing effect between microalgae cells, culture medium, and air bubbles. The methodology involves the cultivation of Spirulina platensis, device fabrication, voltage measurement in both non-aeration and aeration modes, and the use of polarization curves to determine the device performance under a gradually rising external load. The BPV devices are affected by abnormal voltage drop under high external loads, which is called power overshoot. The use of aeration successfully solved the power overshoot issues over time, but it also resulted in a gradual reduction in the voltage output and power density of the BPV devices. During aeration, the BPV devices produced a peak power density of 0.121 ± 0.056 mWm−2 on Day 1, which declined to 0.048 ± 0.025 mWm−2 on Day 13. The blowing of air bubbles had some side effects on BPV devices, including causing the attachment of Spirulina cells to the container walls and accelerating the evaporation of the culture medium. This study emphasizes the role of hydrodynamic aeration in the bioelectricity generation process and opens up possibilities for wider application of BPV devices in renewable energy production.

Enhanced in situ production of Fenton reagent's by nanobubble aeration and sacrificial iron anodes in the electro-Fenton process

Wastewater treatment is currently focused on the development of simple, safe, cost-effective technologies for the complete destruction of persistent organic pollutants. A novel reagent-free electro-Fenton process by integrated nano-bubble aeration and sacrificial iron anode is proposed, which improves mass transferability of large content dissolved oxygen (10.55mgL−1) in the electrolyte and then quickly transported oxygen to the electrode surface. The synergistic effect of nanobubble aeration and sacrificial iron anodes can product a highly efficient hydrogen peroxide (H2O2) (310 mgL−1) and enhanced electrochemically driven reduction of Fe2+ at pH 3.5 and current density 55 mAcm−2. The degradation of phenol (100 mgL−1) with hydroxyl radicals (⋅OH) generated in situ is described by a pseudo first-order kinetics mode and was fast (0.036 min−1), which obtained a remarkable decolorization of over 58.7 % in 60 min. With nanobubble aeration and sacrificial iron anode, the catalytic decomposition of H2O2 to ⋅OH by Fe2+ was more powerful, achieving a cost-effective and green design without reagents.

On the effect of aeration on laser ranging measurements of free water surface

Aerated flows pose both challenges and opportunities in the measurement of free water surface. In this study, an amplitude-modulated continuous wave scanning LIDAR device was used to measure a distance from the device sensor to the water column surface subjected to different degrees of aeration, while reference measurements were performed by high-speed imaging. Different aeration conditions were generated by variation of the air flow rate supplied to the liquid and by using perforated plates with different hole arrangements. The LIDAR device was shown to produce level readings consistently below visible water levels. The measurement error of the LIDAR method is largely determined by the volume fraction of air in water and was lowest at about 0.1 air volume fraction. The error increases linearly until a very high air volume fraction (i.e., above 0.55), while the LIDAR method also performs poorly in unaerated water. Although the measurement uncertainty of LIDAR in the range of aerated water is by at least an order of magnitude higher than in the case of measuring dry solid surfaces, the method is viable for free surface measurement under low to moderate aeration conditions that don't produce excessive foaming.

Treatment of cow manure from exercise pens: A laboratory-scale study of the effect of air injection on conventional and alternative biofilters

Woodchips in stand-off pads for wintering cows have been applied in countries like Ireland and New Zealand. Their primary role is to protect soils by effectively filtering nutrients during wet conditions, while ensuring a healthy and comfortable environment for the cows. The stand-off pad concept has the potential to be adopted in Canada to provide year-long outdoor access to tie-stall dairy cows. The objective of this study was to evaluate the effect of alternative filtering materials and bed aeration under controlled laboratory conditions. Twelve biofilter columns (0.3 m in diameter and 1-m high) were installed in 12 environmentally-controlled chambers (1.2-m wide by 2.4-m long), and divided into four treatments: a bed of conventional woodchips or an alternative mix of organic materials (sphagnum peat moss, woodchips and biochar) with and without aeration (flux rate set at 0.6 m3/min/m2). Approximately 0.6 L of semi-synthetic dairy manure and 1 L of tap water were poured on the biofilters during two experimental periods of 4 weeks, simulating the effect of either winter or summer conditions (room temperature below or over 10 °C) on the retention of nutrients and fecal bacteria. Results showed that the alternative biofilters under both summer and winter conditions were more efficient in removing COD, SS, TN, and NO3–N than conventional biofilters (maximum efficiencies of 97.6%, 99.7%, 96.4%, and 98.4%, respectively). Similarly for E. coli, they achieved a minimum concentration of 1.8 Log10 CFU/100 ml. Conventional biofilters were more efficient for PO4–P removal with a maximum efficiency of 88.2%. Aeration did not have any significant effect under the tested temperature conditions. Additional factors such as media adaptation time as well as aeration flow during this period should be considered.

Effect of aeration on low-substrate CANON process

The completely autotrophic nitrogen removal over nitrite (CANON) is a new type of nitrogen removal process developed in recent years. The control of dissolved oxygen (DO) in this process is relatively stringent, especially in low-substrate wastewater treatment. However, the results of studies on the operation of the process in different aeration modes are still controversial, and investigations on biofilm type CANON reactors are limited. In this study, a pilot-scale CANON bioreactor filled with suspended carriers was investigated on the treatment of wastewater at low ammonium concentrations, and the effect of the aeration mode on autotrophic nitrogen removal was evaluated. Seven conditions with various aeration on/off times and DO levels were tested. The results showed that an intermittent aeration with a 20-min/20-min aeration on/off time and DO concentrations of 1.0–1.3 mg/L at the end of the aeration period was appropriate, potentially inhibiting nitrite oxidizing bacteria (NOB) and keeping the total nitrogen (TN) removal rate at a relatively high level of 76.7% ± 2.5%. In the optimal aeration mode, the reactor achieved effluent TN and NH4+-N concentrations of (11.1 ± 3.3) mg/L and (3.6 ± 2.3) mg/L, respectively, with a hydraulic retention time of 12 h and an influent NH4+-N concentration of (48.6 ± 9.4) mg/L at 30.1°C ± 2.2°C. The results of metagenomic sequencing for microorganisms on carriers indicated that the main nitrogen removal bacteria in the reactor were Proteobacteria, Planctomycetes, and Nitrospirae. The NOB genus Nitrospira was completely inhibited by intermittent aeration. Candidatus Kuenenia had strong adaptability to low-concentration wastewater.

Effects of micro-bubble aeration on the pollutant removal and energy-efficient process in a floc–granule sludge coexistence system

Abstract To investigate energy-saving approaches in wastewater treatment plants and decrease aeration energy consumption, this study successfully established a floc–granule coexistence system in a sequencing batch airlift reactor (SBAR) employing micro-bubble aeration. The analysis focused on granule formation and pollutant removal under various aeration intensities, and compared its performance with a traditional floc-based coarse-bubble aeration system. The results showed that granulation efficiency was positively associated with aeration intensity, which enhanced the secretion of extracellular polymeric substances (EPSs) and facilitated granule formation. The SBAR with the micro-aeration intensity of 30 mL·min−1 showed the best granulation performance (granulation efficiency 52.6%). In contrast to the floc-based system, the floc–granule coexistence system showed better treatment performance, and the best removal efficiencies of NH4+-N, TN, and TP were 100.0, 77.0, and 89.5%, respectively. The floc–granule coexistence system also enriched higher abundance of nutrients removal microbial species, such as Nitrosomonas (0.05–0.14%), Nitrospira (0.14–2.32%), Azoarcus (2.95–12.17%), Thauera (0.43–1.95%), and Paracoccus (0.76–2.89%). The energy-saving potential was evaluated, which indicated it is feasible for the micro-aeration floc–granule coexistence system to decrease the aeration consumption by 14.4% as well as improve the effluent.

Responses of greenhouse gas emissions to aeration coupled with functional membrane during industrial-scale composting of dairy manure: Insights into bacterial community composition and function

Greenhouse gas (GHG) emissions from manure management processes deserve more attention. Using three industrial-scale experiments, this study comprehensively evaluated the effects of different aeration coupled with semi-permeable membrane-covered strategies on the structure and function of bacterial communities and their impact on GHG emissions during dairy manure aerobic composting. The succession of the bacterial communities tended to be consistent for similar aeration strategies. Ruminiclostridium and norank_f__MBA03 were significantly positively correlated with the methane emission rate, and forced aeration coupled with semi-permeable membrane-covered decreased GHG emissions by inhibiting these taxa. Metabolism was the most active function of the bacterial communities, and its relative abundance accounted for 75.69%–80.23%. The combined process also enhanced carbohydrate metabolism and amino acid metabolism. Therefore, forced aeration coupled with semi-permeable membrane-covered represented a novel strategy for reducing global warming potential by regulating the structure and function of the bacterial communities during aerobic composting of dairy manure.

Effect of Aeration on the Cavitation Characteristics of the Control Valve in Hydro-Driven Ship Lifts

In hydro-driven ship lifts, plunger valves and fixed cone valves are the most suitable structures for achieving accurate flow control under a wide range of flow conditions. In order to inhibit cavitation in these valve structures, experiments were conducted in which forced aeration was applied before the valve. The cavitation phenomena and aerated flow regime were observed through a transparent glass pipe, and the cavitation noise characteristics were recorded using a hydrophone. The test results show that aeration can reduce the valve working cavitation number, albeit to a limited degree (<5%). Based on the sound velocity theory of aerated flow and the experimental results, the relationship between the aeration concentration and the cavitation inhibition efficiency was obtained. When the aeration concentration is approximately 0.1%, cavitation can be significantly inhibited via forced aeration before the valve. Once the aeration concentration reaches 0.9%, the cavitation inhibition efficiency becomes saturated. The research results presented in this paper provide a reference for the cavitation inhibition of industrial valves.

Impact of different electrodes, mediators, and microbial cultures on wastewater treatment and power generation in the microbial desalination cell (MDC).

Microbial desalination cell (MDC) can treat wastewater and saline water simultaneously and generate power. The aim of the present research work was to identify the critical factors influencing COD reduction and power generation from the MDC reactor and to optimize the control parameters. The experimental study was conducted by using medium to high-strength wastewater from distillery and brewery industry in batch-wise operation. The maximum voltage of 702 mV and current of 2.16 mA were observed for the carbon brush electrode. The mediated aeration process with the presence of potassium ferricyanide was reported in 87% COD reduction and 992 mV voltage generation. The presence of the microbial culture provided 82% COD reduction and 51% TDS reduction. The maximum current density (CD) of 0.04 mA/cm2 was observed for carbon brush, and a maximum power density (PD) of 15.56 mW/cm2 was found with aeration and potassium ferricyanide mediator. This study provided insight towards the impact of the electrode materials and the effects of mediator, aeration, and microbial culture on MDC performance.

Removal of Ammonium and Phosphate from Synthetic Wastewater of Complex Fertilizer Industry Through Struvite Crystallization Process

The complex fertilizer industry produces wastewater which contributes to the pollution of water bodies because it contains high levels of phosphate and ammonium concentrations and high TKN (Total Kjeldahl Nitrogen) which contains organic nitrogen. The organic nitrogen contained in the complex fertilizer wastewater is urea so it can be hydrolyzed to ammonium using the urease enzyme. The ammonium formed from the hydrolysis of urea will then react with magnesium and phosphate to form struvite, a crystal of Magnesium Ammonium Phosphate (MAP). The purpose of this study was to determine the effect of aeration and the enzyme urease in the removal of ammonium and phosphate in complex fertilizer synthetic wastewater through struvite precipitation. Struvite precipitation was carried out in a batch reactor which had a working volume of 0.5 L with variations in aeration rate, aeration time, and the addition of urease enzyme from Jack bean peas (Canavalia ensiformis). Residual ammonium and phosphate levels were analyzed and struvite crystal formation (MAP) was determined using Scanning Electron Microscope (SEM) and X-ray diffraction (XRD). The results showed that the aeration reactor was able to form struvite crystals and remove the ammonium and phosphate content in the synthetic wastewater of complex fertilizers. The removal of ammonium with a molar ratio of [Mg2+] : [NH4+] : [PO43-] 1:2:1 reached 61-77% at high aeration rates because a lot of ammonium was released into the air. The phosphate removal reached 99%. The urease enzyme was proven to be able to hydrolyze urea into ammonium and increase the pH value and affect the shape of the resulting struvite crystals. The precipitate product obtained was struvite crystals which were confirmed by analysis using SEM-EDX and XRD.