Janusz A. Tomaszek

Dentrification and oxygen consumption in bottom sediments: factors influencing rates of the processes

Rates of denitrification and oxygen consumption were measured in the sediment of four reservoirs in south-eastern Poland using an in situ chamber method. The in situ denitrification rate was calculated from the total N2 flux from sediment, and the rate of oxygen consumption from the differences as a function of time in dissolved oxygen concentration in overlying water enclosed within in situ chambers. Denitrification rates for all the investigated lakes reached 1100 μmol N2 m−2 h−1, and were similar to values reported for eutrophic reservoirs. The rate of oxygen consumption ranged from about 141 to 1890 μmol O2 m−2 h−1. The factors influencing the rate of dentrification and oxygen consumption in bottom sediment such as light, temperature, nitrate and dissolved oxygen concentrations, pH in overlying water and available organic matter in the sediment were investigated. Dentrification rates were enhanced under natural light conditions. Temporal variations in dentrification rate and oxygen consumption appeared to be dominated by temperature. The rates of both processes were greater at 23 °C compared to 12 °C. The higher the concentration of nitrate in overlying water and organic matter in sediment, the greater the rate of dentrification. Orgenic matter concentration did not influence the oxygen consumption rate. Production of nitrous oxide, as the intermediate product of denitrification, was not observed, possibly due to the pH of overlying water (>7.3). A correlation between denitrification rate and oxygen consumption rate was found.

Denitrification in Sediments of a Lake Erie Coastal Wetland (Old Woman Creek, Huron, Ohio, USA)

Denitrification in Old Woman Creek estuary (Lake Erie) sediments was measured by an in vitro N2-flux method with intact cores and by an in situ chamber method. In both methods, nitrogen gas, the end product of denitrification, was measured directly by gas chromatography. The in situ approach allowed measurement of denitrification directly over short time intervals but its use was limited to shallow depths. Denitrification rates measured with in situ chambers agreed well with those from in vitro intact cores when temperatures in the estuary remained constant. However, the two methods could not be accurately compared during the spring when temperature increased rapidly, because of the 4-day pre-incubation time needed for sparging for the in vitro method. In vitro denitrification rates ranged from ca 40 to 135 μmole N2 m−2 h−1 in October 1993 and from 66 to 428 μmole N2 m−2 h−1 in May and July 1994. Oxygen consumption rates in these experiments ranged from 0.71 to 3.0 mmole O2 m−2 h−1. Denitrification rates tended to decrease along the flow axis but differences among stations were usually not significant. In situ N2 accumulation rates ranged from 45 μmole N2 m−2 h−1 in dark chambers during October 1993 up to apparent values of 2,100 μmole N2 m−2 h−1 in May 1994, immediately after the water temperature had rapidly increased to 27°C. These calculated values included gas-solubility corrections due to the water-temperature increases. In situ measurements of denitrification rates in transparent chambers were 76–79% higher than rates measured in a similar dark chamber. The results suggest that denitrification is an important sink for nitrogen in Old Woman Creek estuary and that environmental conditions such as temperature, light, and available substrate affect denitrification rates.

A simple model of nitrogen retention in reservoirs

The total nitrogen mass balance was studied over a two-year period in two reservoirs located in south-eastern Poland. Theobserved nitrogen retention (Nret) inthe reservoirs ranged from 0.18 to 2.12g m-2d-1 (mean 0.83g m-2d-1) in case of theRzeszów Reservoir and from -0.02 to0.41 g m-2d-1 (mean 0.13g m-2d-1) in case of the SolinaReservoir, while the percentage retention(Nret) ranged from 7 to 42% (mean22%) and -15 to 73% (mean 35%),respectively. A good relationship betweenNret and nitrogen loads was observedfor the Solina Reservoir. The data obtainedby the author and collected from theresearches of 6 other reservoirs located insouthern Poland were used to develop anempirical model suitable to predict thenitrogen seasonal dynamics in a reservoir.The model allows for the determination ofboth the annual mean Nret value andits seasonal variation in a reservoir.

In situ chamber denitrification measurements in reservoir sediments: an example from southeast Poland

Abstract Spatial and temporal variations in rates of denitrification were measured in sediments of four man-made lakes, Rzeszow, Solina, Besko, and Wilcza Wola in southeastern Poland using in situ chamber method. Denitrification rate was calculated from the total N2 flux out of the sediment taking into account the correction for the released N2 flux because of the changes in nitrogen solubility. Nitrogen, the final product of denitrification, was measured directly by gas chromatography. N2O, the intermediate product of denitrification, was not observed. Denitrification rates for all the investigated lakes ranged from about 25 to 1100 μmol N2 m−2 h−1 and resembled the values reported for eutrophic reservoirs. Denitrification rates at the upper Rzeszow reservoir stations were generally higher than at the lower ones. Spatial variations in denitrification rates were also observed between stations for Solina and Besko reservoirs. The rates of denitrification for Wilcza Wola reservoir were found to be very low, probably because of compact sediment structure and low substrate availability. Denitrification rate was enhanced under natural light conditions. Temporal variations in denitrification rates appeared to be dominated by temperature. The results suggest that denitrification is an important sink for nitrogen and that environmental conditions such as temperature, light, and available substrate affect denitrification rates. The results presented in this paper indicate that the in situ chamber method should be a useful tool in the studies of denitrification in an aquatic environment.

The significance of denitrification in relation to external loading and nitrogen retention in a mountain reservoir

Nitrogen retention (Nret) and denitrification were studied in the mesotrophic Solina reservoir (south-east Poland) between spring and autumn in 2002 and 2003. Nret was calculated on the basis of the input-output mass balance. The rate of denitrification was measured using the 15N isotope pairing technique in two types of areas; in deep areas, where the bottom sediment makes contacts with the hypolimnion (Dprof), and in the unstratified shallows (Dlitt). The calculated daily load of removed nitrogen (Dtot) varied somewhat from 11.0 to 19.1 mg N m–2 day–1 with a standard deviation of 3.0 mg N m–2 day–1. The limited oscillation noted for Dtot results from the major participation of the deep areas of the reservoir, which are characterised by stable Dprof, as distinct from Dlitt, which varied seasonally from 5.8 mg N m–2 day–1 in November to 109.9 mg N m–2 day–1 in August. The primary factor limiting the denitrification rate was temperature, the other being availability of substrates, mainly organic matter. Nitrogen retention ranged seasonally between –25.0 and 175.9 mg N m–2 day–1. The contribution of denitrification to Nret ranged from 9.0% to 49.8% (mean 16.4%). On average, only 4.9% of the nitrogen external load was denitrified (range 2.6–7.9%, s.d. 1.5%). After comparing obtained data with others available in the literature, we concluded that reservoirs, estuaries and highly-loaded lakes in a river system experience a more limited contribution of Dtot to Nload than is the case in natural lakes.

A study on the use of the BioBall® as a biofilm carrier in a sequencing batch reactor.

Described in this study are experiments conducted to evaluate the removal of organics and nutrients from synthetic wastewater by a moving bed sequencing batch biofilm reactor using BioBall® carriers as biofilm media. The work involving a 15L-laboratory scale MBSBBR (moving bed sequencing batch biofilm reactor) model showed that the wastewater treatment system was based on biochemical processes taking place with activated sludge and biofilm microorganisms developing on the surface of the BioBall® carriers. Classical nitrification and denitrification and the typical enhanced biological phosphorus removal process were achieved in the reactor analyzed, which operated with a volumetric organic loading of 0.84-0.978gCODL(-1)d(-1). The average removal efficiencies for COD, total nitrogen and total phosphorus were found to be 97.7±0.5%, 87.8±2.6% and 94.3±1.3%, respectively. Nitrification efficiency reached levels in the range 96.5-99.7%.

Carbon and nitrogen and their elemental and isotopic ratios in the bottom sediment of the Solina-Myczkowce complex of reservoirs

Carbon and nitrogen and their elemental and isotopic ratios in the bottom sediment of the Solina-Myczkowce complex of reservoirs The studies concerned the ecosystem of the Solina-Myczkowce cascade of reservoirs. While the elemental C:N ratio was higher in the Solina Reservoir branches and in the Myczkowce Reservoir (>10), the values for stations located near the Solina Dam were low (<10). Markedly, the lowest values for δ13C were noted in the Myczkowce Reservoir (-28.5‰), and these contrasted with the higher values found in the Solina Reservoir (ca. -27‰). δ15N varied from 2‰ in the upper Solina to above 3.5-4‰ downstream. While the data obtained indicate the autochthonous origin of sedimentary matter, primary production influences the properties of the bottom sediments in the lower part of the Solina reservoirs.

Denitrification in the sediment of a eutrophic reservoir measured with the isotope pairing technique

Denitrification in the sediment of a eutrophic reservoir measured with the isotope pairing technique Denitrification rates in the bottom sediment of the Rzeszów Reservoir (southeastern Poland) were measured using the isotope pairing technique. At the stations studied rates were reported in the range of about 26 to 610 μmol N2 m-2 h-1, with the figures generally highest in summer. Simple and multiple regression analyses of relationships with selected abiotic factors gave rise to a model that revealed a statistically significant influence on rates of denitrification in the bottom sediment of the Rzeszów Reservoir due to concentrations of nitrate in overlying water, temperature, and the organic matter content in the sediment. The present study confirms that nitrate concentration in the overlying water is the main factor controlling sedimentary denitrification.

The distribution and isotopic composition of carbon and nitrogen as indicators of organic-matter fluxes in the Solina Reservoir (south-east Poland)

The feasibility of using carbon and nitrogen isotope ratios of sediment organic matter (OM) to elucidate the source and fate of bottom sediment was studied in the Solina Reservoir (south-east Poland). Horizontal and vertical changes in OM, total organic carbon (TOC) and total nitrogen (TN) content, as well as δ15N and δ13C values, in bottom sediments were analysed to establish the extent to which these sediments are terrestrial or internal in origin. Increased proportions of TOC along with slight decreases in TN were noted in the surface layer of shallow water sediment compared with the profundal sites. Upstream shallower C : N and δ15N values amounted to ~15 and ~2‰, respectively, pointing to the allochthonous origin of the OM. In turn, profundal C : N ratios of less than 10 and δ15N values of ~4‰ indicated autochthonous sediment. Values for δ13C did not differ between stations and ranged from –27.39 to –27.66‰. It is therefore suggested that the sediment from the upper shallower stations contains more allochthonous, refractory OM, whereas the profundal stations have planktonic OM enriching the sediment. This combined with the vertical distribution observed for δ15N signalled an intensification of eutrophication over the past few years.

Comparison between Sequencing Batch and Continuous Flow Activated Sludge Systems

After introducing fundamentals of periodic processes occurring in sequencing batch reactor (SBR) a comparison of SBR to plug flow reactor (PFR) and completely mixed flow reactor (CMFR) was made.