Increase In Nitrification Rate Research Articles

The Dark Side of Microbial Processes: Accumulation of Nitrate During Storage of Surface Water in the Dark and the Underlying Mechanism.

ABSTRACTIn densely populated cities with limited land, storage of surface water in underground spaces is a potential solution to meet the rising demand of clean water. In addition, due to the imperative need of renewable solar energy and limited land resources, the deployment of floating solar photovoltaic (PV) systems over water has risen exponentially. In both scenarios, microbial communities in the water do not have access to sunlight. How the absence of sunlight influences microbial community function and the water quality is largely unknown. The objective of this study was to reveal microbial processes in surface water stored in the dark and water quality dynamics. Water from a freshwater reservoir was stored in the dark or light (control) for 6 months. Water quality was monitored at regular intervals. RNA sequencing was performed on the Illumina MiSeq platform and qPCR was used to substantiate the findings arising from the sequencing data. Our results showed that storage of surface water in the dark resulted in the accumulation of nitrate in the water. Storage in the dark promoted the decay of algal cells, increasing the amount of free nitrogen in the water. Most of the free nitrogen was eventually transformed into nitrate through microbial processes. RNA sequencing-based microbial community analyses and pure culture experiments using nitrifying bacteria Nitrosomonas europaea and Nitrobacter sp. revealed that the accumulation of nitrate in the dark was likely due to an increase in nitrification rate and a decrease in the assimilation rate of nitrate back into the biomass.IMPORTANCE Microbial communities play an essential role in maintaining a healthy aquatic ecosystem. For example, in surface water reservoirs, microorganisms produce oxygen, break down toxic contaminants and remove excess nitrogen. In densely populated cities with limited land, storing surface water in underground spaces and deploying floating solar photovoltaic (PV) systems over water are potential solutions to address water and energy sustainability challenges. In both scenarios, surface water is kept in the dark. In this work, we revealed how the absence of sunlight influences microbial community function and water quality. We showed that storage of surface water in the dark affected bacterial activities responsible for nitrogen transformation, resulting in the accumulation of nitrate in the water. Our findings highlight the importance of monitoring nitrate closely if raw surface water is to be stored in the dark and the potential need of downstream treatment to remove nitrate.

Effects of Nitrogen Deposition: Results of a Temporal‐Spatial Analysis of Deciduous Forests in South Sweden

Abstract: We studied permanent plots in deciduous forests in two provinces of South Sweden, Skåne (127 plots) and Småland (116 plots). Vegetation data were sampled in 1983 and 1993 and used to calculate weighted averages of Ellenberg indicator values for light, reaction (pH) and nitrogen. Soil samples were collected from all plots in 1993 for determination of pH, organic matter content and potential net nitrogen mineralization (minN). Data on minN were also available for 66 plots in Skåne from 1983. Nitrogen deposition is considerably higher in Skåne than in Småland. The same holds true for total minN, minNH4+, minNO3‐‐, and the proportion of total minN due to nitrate (nitrification ratio). According to the comparison of average Ellenberg indicator values between 1983 and 1993, the stands had become darker (not in the heavily managed plots), more acid and nitrogen rich, except at the most acid sites where only minor changes could be observed. The nitrification ratio was significantly higher in 1993 than in 1983. Mean soil nitrification ratios were determined for the most common species in both regions. The means were higher in Skåne than in Småland. It is likely that nitrogen deposition causes an increase in nitrification rate and nitrification ratio. This ratio is a significant determinant of the species composition in deciduous forests.

Microbial C and N transformations during drying and rewetting of coniferous forest floor material

Microbial C and N transformation rates in air-dried and subsequently rewetted coniferous forest floor material were examined in a laboratory incubation study. Gross N transformation rates were determined through parallel 15NH 4 + and 15NO 3 − enrichment experiments. After drying of the litter for 12 d to a water content of 10% of dry weight, CO 2 respiration, net N mineralization and nitrification rates were strongly restricted. Microbial biomass C was reduced to 67% of the amount in the continuously moist material. Remoistening of the dry litter to a water content of 340% resulted in a flush in C and net N mineralization within a few hours after rewetting. The increase in net N mineralization could be attributed to a larger increase in gross N mineralization relative to the increase in gross N immobilization. Gross N immobilization had increased to the same rate as gross N mineralization after 26 h, and a small secondary peak in respiration and microbial C was observed 48 h after rewetting. It was concluded that both biomass-derived substrate with a low C-to-N ratio and `nonbiomass'-derived substrate with a high C-to-N ratio have been released, and metabolized, as a result of the drying–rewetting treatment. Despite the very extreme drying treatment, the mineralization flush after rewetting could not compensate for the large reduction in CO 2 and mineral N production during dry conditions due to its short duration. Since there was no increase in nitrification rate after drying and rewetting, the NO 3 − concentration at the end of the incubation was strongly reduced due to the extremely slow net nitrification rates during desiccation.

Evaluation of the nitrification rates of microbead and trickling filters in an intensive recirculating tilapia production facility

Downflow floating polystyrene bead (microbead) and trickling media biofilters were tested simultaneously using common influent water from a 53-m 3 fish rearing tank stocked with tilapia ( Oreochromis Nilotica×Aurea) at a density of 168 kg m −3. The physical characteristics of the two bio-filter media used were: (1) 1.0 mm diameter polystyrene spheres with a density of 16 kg m −3 with a specific surface area of 3936 m 2 m −3 (referred to as microbeads); and (2) 5.1 cm diameter polyethylene packing material (Norpak) with a specific surface area of 164 m 2 m −3. Nitrification rates increased linearly with influent total ammonia nitrogen (TAN) concentrations up to a concentration of 2.5 mg l −1 for both the microbead and trickling filters. There was no further increase in nitrification rate above 2.5 mg l −1 that was statistically significant. The trickling filter had a specific nitrification rate 7.5 times higher than the microbead filter, although volumetric nitrification rates were 3.2 times greater for the microbeads than the trickling filter. The study failed to show any relationship for either type of filter between the hydraulic loading rate and the nitrification rate at hydraulic loading rates between 469 and 1231 m 3 m −2 day −1.

Nitrification of landfill leachate using suspended-carrier biofilm technology

The possibility of nitrifying municipal landfill leachate using suspended-carrier biofilm technology was studied in three laboratory-scale reactors filled with three different types of carrier media. The effects of the temperature and the hydraulic retention time (HRT) on the volumetric nitrification rate were investigated. Steady-state nitrification rates were obtained in the processes after approximately 1 month of operation. The nitrification rate showed a rather weak dependence on the temperature, the rate at 5°C being approximately 77% of the rate at 20°C. The HRT had a more pronounced effect on the rate of nitrification, showing a considerable increase in nitrification rate with a decreased HRT. The highest efficiency was achieved for a carrier media consisting of small cubes of macroporous cellulose. A maximum nitrification rate of 40 g (NH + 4-N)/(m 3 reactor h) was obtained by use of this carrier at 20°C, an HRT of 14 h and a carrier filling degree of 10% of the reactor volume.

Reduction of ammonia volatilization from urea by rapid nitrification

Abstract Loss of NH3 from urea fertilizer in a cultivated sandy desert soil was evaluated by using various fertilizer treatment regimes. The nitrification of added urea increased with the pretreatment of (NH4)2SO4. The increase in nitrification rate was directly related to the amount of (NH4)2SO4 added. These results suggested that when urea was applied after sufficient increase in nitrification rate, i.e., 3 to 5 weeks after the pretreatment with NR+ 4 fertilizers, the NH+ 4 produced by the hydrolysis of urea was quickly nitrified, leaving low concentration of NH+ 4 in soil and resulting in decreased losses of NH3. Among the different NH+ 4 containing or forming fertilizers, (NH4)2SO4 was significantly better in arresting NH3 loss from a subsequent application of urea. The decreased loss of N was reflected in higher yields of pearl millet.

Nitrification in soils incubated with pig slurry or ammonium sulphate

The effects of temperature, moisture content and the addition of pig slurry on nitrification in two soils were studed. There was no accumulation of NO 2 −-N under the incubation conditions investigated and the accumulation of NO 3 −-N was linear for additions of 50–250 μg NH 4 +-N g − soil, either as ammonium sulphate or as pig slurry. Nitrate formation was treated as a single step, zero order process to enable a rate constant to be calculated. Nitrification rate increased with increasing moisture content up to the highest level tested, soil water potential −8.0 kPa, corresponding to approximately 60% of water holding capacity in both soils. Measurable nitrification was found in both soils at the lowest moisture content (soil water potential −1.5 MPa) and temperature (5° C) tested. The nitrification rate constant in soils treated with 50 μg NH 4 +-N g − soil was not significantly affected ( P = 0.05) by the form of ammonium added. Addition of 250 μg NH 4 +-N as ammonium sulphate caused a marked inhibition of nitrification at all moisture contents and temperatures. Addition of 250 μg NH 4 +-N as pig slurry caused a marked increase in nitrification rate, the increase being greater at the higher temperatures and moisture contents.