Ammonia Concentration In Water Research Articles

Digestible protein levels and metabolic responses in juvenile piapara (Megaleporinus obtusidens)

The piapara (Megaleporinus obtusidens) is an omnivorous fish with great market potential. However, little is known about its dietary requirements. This study aimed to determine the effects of dietary protein on growth and physiological indicators in piapara. Three hundred piapara juveniles (24.0 ± 1.3 g) were distributed in 20 tanks of 130-L (15 fish/tank) provided with continuous aeration and water. Five isoenergetic diets (14.0 MJ/kg) were formulated to contain increasing levels of digestible protein (21, 24, 27, 30, and 33% DP). After 77 days, weight gain and ammonia concentration in water were found to increase linearly with increasing digestible protein (DP) level (p<0.05). Protein productive value (PPV) reached a maximum at 28.4% DP. No relationship was found between DP level and serum ammonia, liver alanine aminotransferase (ALT) activity, hepatosomatic index (HSI), liver glycogen (GL) or liver lipid (LL) content (p>0.05). Mesenteric fat index (MFI) and liver malic enzyme (ME) activity followed a quadratic pattern (p<0.05) and reached a maximum at 25.8% and 27.1% DP, respectively. Muscle lipid (ML) content decreased linearly with increasing DP level (p<0.05), whereas liver glucose-6-phosphate dehydrogenase (G6PD) activity decreased linearly as DP level increased (p<0.05). Results showed that a diet containing 28.4% PD provides better crude protein retention efficiency and reduces amino acid deamination in M. obtusidens. Low protein diets increased energy retention efficiency, whereas fish fed high protein diets had higher ammonia excretion.

Tunable and ultrasensitive sensor covering terahertz to telecommunication range based on a Fabry–Perot interference of graphene plasmonic waves

We present an ultrasensitive tunable terahertz (THz) sensor that comprises monolayer graphene-based gratings integrated with a Fabry-Perot (FP) cavity through precisely numerical modeling. Due to the vertical polarization of the incident light on the graphene gratings, they act as an electric dipole, which causes interference in the propagation of plasmonic waves, and provides an excellent foundation for a wide range of ultrasensitive refractive index (RI) sensing with an ultra-high-quality factor (Q). The main advantage of the proposed structure is not only sensing a wide range of refractive indices but due to its unique physical mechanism, it covers electromagnetic waves from a few terahertz to 300 THz, including the telecommunication bands. The primary physical mechanism in the proposed sensor is the FP interference in its active area. Also, due to the extreme sensitivity of FP interference (FPi) to the (RI) of the medium and the active area, the proposed structure owns an ultra-high sensitivity and Q. Our full-wave electromagnetic simulations demonstrate a frequency sensitivity of up to 83 THz per RI unit (RIU) and a high value of Q near 275. In addition, the proposed structure for index sensing has the functionality to be tuned in any desired frequency of interest from THz to the Mid-IR range and telecommunication band, which entirely covers 1–300 THz. The chemical potential of graphene can be electrically controlled to tailor the sensing capability and incident frequency. According to the applied gate voltage, the proposed structure can detect ammonia concentration in water with a high sensitivity of 70–85 THz/RIU and a quality factor of more than 275. The error of the ammonia concentration sensing is smaller than 0.5%. In addition, the proposed structure can detect different types of matter, including various microfluidics, air, gasoline, liquid paraffin, ethanol, glycerin, and glucose. The graphene plasmonic grating method suggested here is a good contender for on-chip integrated THz to mid-IR, including telecommunication bio-sensors.

Rapid and sensitive detection of ammonia in water by a long period fiber grating sensor coated with sol-gel silica.

A sensitive ammonia sensor based on long-period fiber grating (LPFG) is designed and manufactured for the detection of ammonia concentration in water. Femtosecond laser direct writing technology is used to write LPFGs on standard single-mode silica fiber. A thin layer doped with basic dyes is coated on the optical fiber for sensing by using the sol-gel method. The thicknesses of sol-gel layers, which play a key role in the sensitivity of the LPFG sensor, were carefully studied. Experimental results show that LPFG with a functional layer of ∼340 nm has the best sensing performance, and the detection limit is 0.08 ppm. The response time of the sensor is less than one minute, and the sensor has good repeatability with a short recovery time. Compared with other organic molecules and ions in water, the proposed LPFG sensor has not only good reusability, but also selectivity for the detection of ammonia.

Influence of diet and feeding strategy on the performance of nitrifying trickling filter, oxygen consumption and ammonia excretion of gilthead sea bream (Sparus aurata) raised in recirculating aquaculture systems

Gilthead sea bream (Sparus aurata) was raised in six individual recirculating aquaculture systems (RAS) whose biofilters’ performance was analyzed. Fish were fed with three different diets (a control diet, a fishmeal-based diet (FM), and a plant meal-based diet (VM)) and with three different feeding strategies (manual feeding to apparent satiation, automatic feeding with restricted ration, and auto-demand feeding). For every combination of diet and feeding strategy, the mean oxygen consumption, ammonia excretion, and ammonia removal rate were determined. Fish fed with the VM diet consumed the most oxygen (20.06 ± 1.80 gO2 consumed kg−1 day−1). There were significant differences in ammonia excretion depending on the protein content and protein efficiency of the diet, as well as depending on feeding strategy, which in turn affected ammonia removal rates. Fish fed by auto-demand feeders led to the highest mean ammonia removal rate (0.10 gN-TAN removed m−2 biofiltration area day−1), while not leading to peaks of high ammonia concentration in water, which preserve fish welfare and growth.

Optical Detection of Ammonia in Water Using Integrated Up-Conversion Fluorescence in a Fiberized Microsphere

A novel optical sensor for ammonia concentration in water is demonstrated using up-conversion (UC) fluorescence intensity ratio (FIR). The sensor element consists of (i) an Er3+-Yb3+ co-doped tellurite glass microsphere integrated inside a section of suspended tri-core hollow fiber (STCHF) and (ii) the pH indicator phenol red. When 980 nm pump is coupled into the microsphere, the Er3+ ions produce green and red UC emissions. Exposure to ammonia results in a strong increase in the 560 nm absorption of the phenol red, which acts as a filter for the green emission, while the red emission is unaffected. A simple linear relation between the FIR and the ammonia aqueous concentration has been established.

Analysis of Ammonia in Kali Lamong River Estuary Surabaya during Pandemic Covid-19

Water quality monitoring is an important instrument in the management of freshwater resources because they offer essential information about the physical, chemical, and biological water resources status, determining patterns and changes over time, and identifying emerging water quality issues especially in a specific situation. This study investigates the ammonia concentration in Kali Lamong river estuaries Surabaya to comprehensive the level of pollution that occurs during pandemic Covid-19. This research was conducted in the river downstream of Kali Lamong in the dry season. Sampling has occurred in 3 stations. Each station has 3 sampling sites that were ¼ of the left side, ½ from the side of the left, and ¼ of the right side. The measurement ammonia in water was measured by SNI 06-6989.30-2005 method. The laboratory result depicted the highest of ammonia concentration (0.765 mg/L) at B1 site. The ammonia concentration in water was <0.02 to 0.13 mg/L in another site. The water sampling result was classified based on PP number 22 of 2021 implementation of protection and management of environment in sixth appendix about national water quality standard with third-class purpose.

RAINBOW TROUT: BIOTECHNOLOGICAL AND GENETIC ASPECTS OF FARMING AND BREEDING

An important problem of fish farming in is the accumulation of organic matter and ammonia in the water reservoir. Breeding work in fish populations is carried out using both mass selection and individual selection in families (family selection). Data on the genetic characteristics of trout, such as natural polyploidy and high genetic variability at quantitative traits, are presented. The purpose of the review is to consider the issues of modern technology for fish breeding to show the fesibility of bacterial water purification during its recirculation in water systems, to summarize the latest achievements of genetics and biotechnology that have found application in industrial fish farming in the country. The review considers biotechnological solutions to the problem of the accumulation of organic substances and ammonia in water by fish breeding and selection of effective bacterial strains that make it possible to utilize these harmful substances, thus, reducing their concentration in water to an acceptable level. In this regard, the Dyadobacter sp. and Janthinobacterium sp., which, when used in combination, provide a comfortable environment for growing Rainbow Trout. At the same time, the concentration of ammonia in water declines from 13.2 ± 2.1 μg/ml to 8.8 ± 1.8 μg/ml, which meets the normative values. Thus, the review presents a detailed picture of the biological characteristics of trout fish, showing their potential for further genetic, breeding, and biotechnological research.

Activation of peroxymonosulfate by cobalt doped graphitic carbon nitride for ammonia removal in chloride-containing wastewater

• The Co-g-C 3 N 4 /PMS/Cl process is an effective method for ammonia removal. • Cl • is proved to play a major role in ammonia removal. • Ammonia is mainly converted to nitrogen gas. • The Co-g-C 3 N 4 catalyst exhibits a great stability and reusability. Ammonia is one of the main nitrogen pollutants in water, and a low concentration of ammonia in water is relatively difficult to remove. The catalytic system activating peroxymonosulfate (PMS) by the cobalt doped graphitic carbon nitride (Co-g-C 3 N 4 ) was established for the oxidation of ammonia. The high removal efficiency of 98.3% for ammonia can be achieved, and total nitrogen removal efficiency was approximately 76.1% in the Co-g-C 3 N 4 /PMS/Cl process. Sulfate radical (SO 4 •− ) was generated during the Co-g-C 3 N 4 /PMS process, reacting with chloride ions to produce chloride radical (Cl • ), which was identified as the main radical species for the transformation of ammonia to nitrogen gas. Moreover, Co-g-C 3 N 4 had a good stability and can be recycled and reused owing to the Co-N bond. The results demonstrated the Co-g-C 3 N 4 /PMS/Cl process was an efficient and promising method for the removal of ammonia in chloride-containing wastewater under ambient conditions.

Nitrogen fertilizer reduction in combination with Azolla cover for reducing ammonia volatilization and improving nitrogen use efficiency of rice.

BackgroundExcessive nitrogen (N) application rate with low N use efficiency (NUE) caused a considerable amount of N losses, especially ammonia volatilization (AV). Proper N fertilizer reduction (RN) could significantly reduce AV. However, continuous RN led to a nutrient deficiency in the soil and therefore negatively impacted the NUE and rice yield. Paddy Azolla, a good green manure, is considered as a promising measure to decrease AV and improve NUE and grain yield of rice. However, there is limited information on the integrated effects of RN and Azolla cover on the AV, NUE, and rice yield, especially in the highly fertilized rice-growing systems.MethodsThe experiment was conducted including eight treatments: the control (without N fertilizer and Azolla cover), Azolla cover without N fertilizer (A), farmer’s N application rate (FN), FN + Azolla cover (FNA), 15% RN from FN (RN15), RN15 + Azolla cover (RN15A). 30% RN from FN (RN30), RN30 + Azolla cover (RN30A). The integrated effects of N fertilizer reduction and Azolla cover on AV, NUE, and rice grain was evaluated.ResultsRN15A and RN30A substantially reduced total AV by 50.3 and 66.9% compared with FN, respectively, primarily due to the lower surface water ammonia concentrations and pH. RN improved the efficiency of Azolla cover on reducing AV, with 4.1–9.9% higher than for FN. Compared with the FN, RN15A and RN30A enhanced apparent N recovery efficiency (ANRE) by 46.5 and 39.1%, which might be responsible for the lower NH3 emission and the increased total N uptake / total chemical N applied. Furthermore, RN15A and RN30A reduced yield-scaled volatilization by 52.3 and 64.3% than for FN, respectively. Thus, combining 15–30% RN with Azolla cover may be a way to reduce AV and improve ANRE without decreasing rice grain yield.

Mobile digital colorimetry for the determination of ammonia in aquaculture applications

Because of the increasing need for healthy and safe foods, the interest for aquaculture is growing. This is a low carbon trace approach to produce animal protein, but the efficiency of a farm depends on controlling a set of parameters related to the quality of the water. One of the most important parameters to keep under control in water is the concentration of ammonia, which increases by the accumulation of fish excretions and the decomposition of leftover food. Determining the ammonia concentration in water often requires expensive equipment and experienced technicians, which is prohibitive for many aquaculture producers. We present a methodology to estimate the ammonia concentration of the water from an aquaculture pond. First, we prepare a water sample using a filter and three chemical reagents. The water sample acquires a coloration that is related to the concentration of ammonia in the water. Then, a mobile application is used to capture an image of the colored sample, which is subjected to a digital colorimetry procedure to estimate the ammonia concentration in the water sample. This approach requires inexpensive consumables, and the aquaculture producer requires little training to perform the measurements. Also, the mobile device is something that the aquaculture producer may already have. Even though the camera sensors in commercial mobile devices are far from being accurate measuring instruments, the tests conducted shown that our methodology can estimate the ammonia concentration in water with enough accuracy to determine when the water in the aquaculture pond needs to be replaced.

Prediction of ammonia concentration in water based on microwave spectroscopy

Ammonia is a common pollutant in water as the result of runoff in agricultural areas where it is applied as fertilizer. It must be monitored regulary for safety purpose. The current testing technique does not allow on-site measurement as the equipment are bulky, the measurement process is time-consuming and tedious with additional mixing reagents. In this study, the presence of ammonia in distilled water is estimated from open-ended coaxial probe in the range of 200 MHz to 14000 MHz. Experimental results were obtained from two set of samples with seven different ammonia concentration each. The measurements are repeated thrice hence producing forty-two data sets with 550 points. Both curve fitting and multiple regression analysis were considered to perform valid ammonia concentration projection. Validation based on 5-fold and 10-fold cross validation suggested the feasibility of the technique as it presents root mean square error (RMSE) which is less than 0.02 in the ammonia prediction. Detection method based on open-ended probe would be convenient, simple and accurate method for in-situ determination of ammonia concentration.

Real-time advanced spectroscopic monitoring of Ammonia concentration in water

A direct method for real-time monitoring of Ammonia (NH3) concentration in fish ponds is demonstrated in this study. The method is based on monitoring the spectral signature of pure NH3 in the mid and far infrared (MIR and FIR, respectively) spectrum. A vacuum pump was used to evaporate the pond water. The evaporated water was transferred to a special gas cell for spectroscopic measurement. A linear relationship between NH3 concentration during the evaporation process and the detected signal was found. NH3 concentrations in the order of 1 PPM were detected with excellent agreement (<± 5%) to conventional methods. Further improvement model can be achieved if longer interaction paths are used. The advantages of the presented method are: direct measurement of NH3 rather than the indirect calculations and measurements currently used. Better accuracy, and real-time operation is achieved with no maintenance required. The disadvantages of the suggested method are: need for calibration and minor complexity with the vacuum unit.

Biotechnological Approaches for Intensification of Ammonium Removal During Drinking Water Treatment

Background. Nitrogen-containing substances are the most common components of groundwater of Ukraine. It was detected, that ammonium may impact on the process of water disinfection, the appearance of nitrite in the distribution system and the problem with the taste and smell of water. The presence of high concentrations of nitrites and nitrates in water can cause methemoglobinemia in children that causes cyanosis and asphyxia. So, there is an urgent demand of developing approaches to intensification of ammonia removing from drinking water. Objective. The aim of these studies is to examine the characteristics of biotechnological processes of nitrogen compounds removing from drinking water in its purification with charge BIOFILTER. Methods. The object of the study was underground water from wells located in the Khmelnitsky region. The initial concentration of ammonia in water was 2.16 mg/dm 3 , nitrite – 0.48 mg/dm 3 , nitrate – 4.5 mg/dm 3 . Investigation of removing of nitrogen-containing substances was conducted on a pilot plant, consisting of aerator, closed contact tank and model filters with charge BIOFILTER. Water was saturated with oxygen in water aerator then came to closed contact tank, where the following parameters were gauged: the concentration of dissolved oxygen, ammonia, nitrites and nitrates. The concentration of dissolved oxygen, ammonia, nitrites and nitrates were controlled in the output water. The pilot plant was set up and worked on the well. Results. It is shown that when the concentration of oxygen decreased from 8.0 to 6.4 mg/dm 3 , a sharp decrease in nitrate concentrations from 4.5 to 3.9 mg/dm 3 was observed. A gradual decrease of nitrates concentrations was observed with increasing doses of consumed oxygen. It was suggested that the nitrification process was passing simultaneously with a process of denitrification as evidenced by a sharp decrease in the concentration of nitrates with a decrease in the oxygen dissolved in water. Conclusions. A decrease in dissolved oxygen concentration violates theoretical ratio of nitrate content in water was experimentally confirmed. The actual content of nitrates in the treated water was less than the theoretical, indicating the passage of denitrification process simultaneously with a process of nitrification. The less concentration of dissolved oxygen in the water at the outlet of the filter, the deeper denitrification is held.

An ammonia sensor based on Lossy Mode Resonances on a tapered optical fibre coated with porphyrin-incorporated titanium dioxide

The development of a highly sensitive ammonia sensor is described. The sensor is formed by deposition of a nanoscale coating of titanium dioxide, containing a porphyrin as a functional material, onto a tapered optical fibre. The titanium dioxide coating allows coupling of light from the fundamental core mode to a lossy mode supported by the coating, thus creating a Lossy Mode Resonance (LMR) in the transmission spectrum. A change in the refractive index of the coating caused by the interaction of the porphyrin with ammonia causes a change in the centre wavelength of the LMR, allowing concentrations of ammonia in water as low as 0.1ppm to be detected, with a response time of less than 30s.

High sensitivity sol-gel silica coated optical fiber sensor for detection of ammonia in water.

A high sensitivity ammonia sensor based on a tapered small core singlemode fiber (SCSMF) structure for measurement of ammonia concentration in water is reported. Two tapered SCSMF fiber structures with different waist diameters of 23 µm and 13.5 µm are fabricated by using a customized microheater brushing technique. The silica based material prepared by the sol-gel method is used as a coating applied to the surface of the tapered fiber structures. To investigate the influence of the coating thickness on the sensitivity to ammonia in water, silica coatings with different thicknesses (2-pass and 8-pass coatings) are deposited on the surface of the fiber sensor with a waist diameter of 23 µm. Experiments demonstrate that the sensor with a thicker (8-pass) silica coating shows better sensitivity of 0.131 nm/ppm to ammonia compared to that of 0.069 nm/ppm for the thinner silica coating (2-pass). To further improve the sensor sensitivity, the taper waist diameter is reduced. For an 8-pass coating (249nm at the taper waist section) applied to a tapered SCSMF structure based fiber sensor with a reduced waist diameter of 13.5 µm. Experimental results show that the sensitivity to ammonia is significantly improved to 2.47nm/ppm. The best measurement resolution for ammonia concentration in water is estimated to be 4 ppb while the response and recovery times are less than 2 and 5 minutes respectively. The proposed sensor also offers good performance in terms of repeatability and good selectivity for sensing ammonia compared to that of other common ions and organic molecules in water.

The Impact of Component Modification of “Double Bottom Filter” Recirculation System to Concentration of Ammonia in Water and Survival Rate at Rearing Media of Blue Devil Fish (Chrysiptera cyanea)

Blue devil (Chrysiptera cyanea), blue damselfish, is a variety of marine ornamental fish. In rearing ornamental fish, water quality management is required to maintain the optimal condition of water quality. Filtration and recirculation are proven as preeminent ways to manage the optimal condition of water quality in aquarium as the vessel for rearing ornamental fish. Simple recirculation system double bottom filter was applied in this research with treatments of components modification of the system. The objective of the research was to identify the concentration of ammonia in rearing media of blue devil (C. cyanea) using recirculation system double bottom filter with several modification components. The treatments are i.e. (1) no recirculation/aeration only (treatment A), (2) system with components of sand and dacron (treatment B), (3) sand and sponge (treatment C). The result showed that the ammonia concentration in system A (control) was 0.890 mg/L, system B (sand and dacron) was 0.129 mg/L, and system C (sand and sponge) was 0.7 mg/L. The highest value of survival rate was in system B (components sand and dacron) which valued 90%. As the conclusion, component sand and dacron in recirculation system double bottom filter provided better performance in reducing ammonia in rearing media of blue devil (C. cyanea) which also confirmed with the survival rate value.

Trace ammonium removal by liquid–liquid membrane contactors as water polishing step of water electrolysis for hydrogen production from a wastewater treatment plant effluent

AbstractBACKGROUNDThis work evaluates hollow fiber liquid–liquid membrane contactors (HFMC) as a polishing step for the removal of low levels of ammonium from water purified by (or being supplied to) a membrane distillation unit in order to fulfil the conductivity requirements of hydrogen production by water electrolysis.RESULTSThe influence of the operating conditions (flow, pH, ammonium concentration, buffer capacity) were evaluated under a closed‐loop setup in order to achieve a reduction of total ammonia concentration in water, from 15 to 1 mg L−1 to assure the production of water in the membrane distillation with a conductivity lower than 1 µS cm−1. These values were used to validate a numerical algorithm describing the system performance. In order to reach the ammonia concentration requirements and considering the low concentration of bicarbonate (low pH buffer capacity) in the treated water a buffer agent was added to the working solution.CONCLUSIONSHFMC technology is a suitable solution to remove low levels of ammonium from water to values as low as 1 mg L−1NH3 through appropriate control of pH. The ammonium removal efficiency of the HFMC was improved by raising the pH or the flow rate. Finally, the model proposed provides a good description of the membrane contactor performance with minimal deviations when compared with experimental results. © 2016 Society of Chemical Industry

Effects of altering dietary protein content in morning and evening feedings on growth and ammonia excretion of red drum (Sciaenops ocellatus)

Two consecutive 8-week growth trials were undertaken to compare effects of different feeding regimes in which dietary protein content was varied on a daily or weekly basis on growth performance, protein utilization and nitrogenous waste production of red drum (Sciaenops ocellatus). Three isoenergetic practical diets were formulated to contain 30% (P30), 35% (P35) or 40% (P40) crude protein (CP) levels (dry-matter basis) and fed to juvenile fish in these two experiments. In the first trial (trial 1), the P40 diet together with the P35 or P30 diet were alternatively fed in the morning (a.m.) and evening (p.m.) to form five different experimental treatments (amP40/pmP40, amP35/pmP40, amP40/pmP35, amP30/pmP40, amP40/pmP30). In trial 2, the amP40/pmP40, amP35/pmP40, amP40/pmP35 treatments of trial 1 were repeated, and two new treatments were added by alternating the P40 diet daily (DP40/DP35) or weekly (WP40/WP35) with the P35 diet. Juvenile red drum (average initial weight of 2.98 g/fish in trial 1 or 3.44 g/fish in trial 2) were stocked as groups of 15 fish in 110-L aquaria containing brackish water (7 g/L) and operated as a recirculating system. Fish in triplicate aquaria were fed each dietary treatment at a rate approaching apparent satiation for 8 weeks. Nitrogenous waste was evaluated by monitoring water ammonia concentration (g/kg body weight) 6-h postprandial at the end of the first growth trial. Replacing the P40 diet with the P30 diet in the morning (a.m.) or evening (p.m.) feeding significantly (p < 0.05) reduced fish growth performance; whereas, weight gain of red drum fed the P40 diet both at a.m. and at p.m. showed no significant (p ≥ 0.05) differences compared to fish fed the P35 diet at a.m. and the P40 diet at p.m. or fish fed the P40 diet at a.m. and the P35 diet at p.m., or fish fed the P40 diet and P35 diet alternating on a daily or weekly basis. Indices of body condition as well as protein intake, protein efficiency ratio, protein productive value and muscle ratio did not vary remarkably among experimental treatments. Plasma thyroid hormones triiodothyronine (T3) and tetraiodothyronine (T4) as well as ammonia concentrations also did not show significant (p ≥ 0.05) differences among experimental treatments; however, water ammonia production 6-h post a.m. or p.m. feeding from fish fed the P40 diet were significantly (p < 0.05) higher than those of fish fed the P35 or P30 diets.

Factors influencing nitrification in point-of-use BioSand filters

The BioSand filter (BSF) is a point-of-use treatment technology used in developing countries to improve drinking water quality. Studies on the BSF to date have mainly focused on bacterial, protozoan and virus reduction and less on the filter's effect on chemical contaminants that may also affect human health. This study explored the potential for nitrification in field-scale trials of four BSFs treating water from a covered drilled well in rural Cambodia. The effect of raw water ammonia concentration (0.4 to 18 mg-N/L) and filter idle time (2 and 24 h) were investigated. Incomplete nitrification was observed in both control and test BSFs as inferred from nitrite and nitrate measurements. At the highest ammonia loading (18 mg-N/L), the sum of ratios of nitrite and nitrate in BSF effluent exceeded the World Health Organization's limit by as much as 40%, but only due to the presence of 1.5 mg-N/L nitrate in the influent. Three methods for minimizing nitrite and nitrate in filtered water were evaluated, including wasting certain fractions of filtered water that may have higher concentrations, cleaning the BSFs and allowing filtered water to aerate for a period of time. None of these methods were deemed to sufficiently counteract potential nitrification.

The effects of dredging on nitrogen balance in sediment-water microcosms and implications to dredging projects

Sediment dredging is a controversial technology for eutrophication control. It is necessary to understand its environmental effectiveness and mechanisms. In this study, sediments from un-dredged (UDR), fresh-dredged (FDR) and post-dredged (PDR, 3 years later) regions of Dongqian Lake were collected to compose sediment-water microcosms for evaluating the effects of dredging on nitrogen cycling. From 0 to 19 days, ammonia in the overlying water greatly increased in UDR (603.1%) and FDR (269.3%), but slightly in PDR (88.7%). The increase of ammonia concentration in water was negatively correlated with DO which was higher in two dredged groups than that in un-dredged groups. These results suggest that dredging could lead to ammonia release to water column in a short term, while ammonia release risk is low few years after dredging. In addition to high DO content, high Eh values, low pH and sediment porosity in two dredged groups may weaken the attenuation of nitrate. TN contents in both sediment and overlying water indicate that nitrogen lost in un-dredged group while had no significantly change in two dredged groups, indicating the ability of nitrogen removal in dredged groups was weakened. Our study suggests that dredging may have potentials to weaken nitrate and/or nitrogen removal from lake systems over years. For this, we should pay more attention on dredging area in dredging projects. Moreover, dredging is better to be conducted in low temperature seasons after blocking external nutrient loadings.