Search results for "nitrifikaatio"
showing 10 items of 29 documents
Seasonal cycle of benthic denitrification and DNRA in the aphotic coastal zone, northern Baltic Sea
2020
Current knowledge on the seasonality of benthic nitrate reduction pathways in the aphotic, density stratified coastal zone of the Baltic Sea is largely based on data from muddy sediments, neglecting the potential contribution of sandy sediments. To gain a more comprehensive understanding of seasonality in this part of the Baltic Sea coast, we measured rates of benthic denitrification, anammox and dissimilatory nitrate reduction to ammonium (DNRA) monthly in the ice-free period of 2016 in both sandy and muddy aphotic sediments, northwestern Gulf of Finland. No anammox was observed. The seasonal cycle of denitrification in both sediment types was related to the hydrography-driven development …
The effects of different combinations of fixed and moving bed bioreactors on rainbow trout (Oncorhynchus mykiss) growth and health, water quality and…
2019
Abstract The effect of bioreactor design on nitrification efficiency has been well studied, but less is known about the overall impacts on water quality. Besides nitrification, submerged fixed bed bioreactors (FBBR) trap fine solid particles, whereas moving bed bioreactors (MBBR) grind solids, possibly increasing solids and particle accumulation in the system. In this experiment, the effects of different combinations of fixed bed and moving bed bioreactors on water quality, solids removal, particle size distribution, fish health based on histopathological changes and nitrification efficiency were studied in laboratory scale recirculating aquaculture systems (RAS) with rainbow trout (Oncorhy…
Methylophaga and Hyphomicrobium can be used as target genera in monitoring saline water methanol-utilizing denitrification.
2016
Abstract Which bacterial taxonomic groups can be used in monitoring saline water methanol-utilizing denitrification and whether nitrate is transformed into N2 in the process are unclear. Therefore, methylotrophic bacterial communities of two efficiently functioning (nitrate/nitrite reduction was 63–96 %) tropical and cool seawater reactors at a public aquarium were investigated with clone library analysis and 454 pyrosequencing of the 16S rRNA genes. Transformation of nitrate into N2 was confirmed using 15N labeling in incubation of carrier material from the tropical reactor. Combining the data with previous study results, Methylophaga and Hyphomicrobium were determined to be suitable targe…
Denitrification and dissimilatory nitrate reduction to ammonium in a lake receiving wastewater effluent
2015
Denitrifikaatio ja DNRA (dissimilatory nitrate reduction to ammonium) ovat nitraattia pelkistäviä prosesseja, jotka yleensä esiintyvät hapettomissa olosuhteissa, kuten järvien sedimenteissä ja alusvesissä. Denitrifikaatiossa syntyy typpikaasua, joka poistuu ilmakehään, kun taas DNRA:n lopputuote on ammonium, joka jää veteen. Luonnollinen denitrifikaatio voi poistaa typpeä jätevedenpuhdistamon poistovedestä, mutta DNRA:n rooli on vähemmän tunnettu. Näiden prosessien tutkiminen voi auttaa jätevedenpuhdistuksen kehittämisessä. Tässä Pro Gradu –työssä tutkittiin denitrifikaation ja DNRA:n prosessinopeuksia sekä nopeuksien korrelaatioita erilaisten vedenlaatumuuttujien kanssa. Tutkimuspaikkana o…
Sediment diffusion method improves wastewater nitrogen removal in the receiving lake sediments
2018
Sediment microbes have a great potential to transform reactive N to harmless N2, thus decreasing wastewater nitrogen load into aquatic ecosystems. Here, we examined if spatial allocation of the wastewater discharge by a specially constructed sediment diffuser pipe system enhanced the microbial nitrate reduction processes. Full-scale experiments were set on two Finnish lake sites, Keuruu and Petäjävesi, and effects on the nitrate removal processes were studied using the stable isotope pairing technique. All nitrate reduction rates followed nitrate concentrations, being highest at the wastewater-influenced sampling points. Complete denitrification with N2 as an end-product was the main nitrat…
Functional gene pyrosequencing reveals core proteobacterial denitrifiers in boreal lakes
2015
Denitrification is an important microbial process in aquatic ecosystems that can reduce the effects of eutrophication. Here, quantification and pyrosequencing of nirS, nirK, and nosZ genes encoding for nitrite and nitrous oxide reductases was performed in sediment samples from four boreal lakes to determine the structure and seasonal stability of denitrifying microbial populations. Sediment quality and nitrate concentrations were linked to the quantity and diversity of denitrification genes, the abundance of denitrifying populations (nirS and nosZ genes) correlated with coupled nitrificationdenitrification (Dn), and the denitrification of the overlying water NO3 − (Dw) correlated with the n…
Startup and effects of relative water renewal rate on water quality and growth of rainbow trout (Oncorhynchus mykiss) in a unique RAS research platfo…
2018
Abstract The aquaculture industry is growing fast but facing two major challenges: a shortage of suitable locations for growth and the need to reduce environmental impacts. One solution for both these challenges is inland production through recirculating aquaculture systems (RAS). The RAS technique is rather new, and several practical issues need to be solved. In this study, an experimental platform, consisting of ten individual RAS units, was built for small-scale testing of different RAS designs and operation methods, and two preliminary experiments were conducted. In the first experiment, the capability of different chemical additions (sodium nitrite, ammonium chloride and/or cane sugar)…
The effect of plants on microbes, water quality, and fish performance in an aquaponic system
2023
Aquaponics is a way to utilize the nutrient-rich effluents from recirculating aquaculture systems (RAS) by combining hydroponics, i.e. soilless plant farming, with RAS. The plants in aquaponics can be grown as a single or mixed plant species together with fish. In this dissertation, I investigated if plant growth is affected in aquaponics compared to hydroponics and if the plants affected the growth and microbial communities in rainbow trout (Oncorhynchus mykiss) or water quality in aquaponics compared to RAS. The first experiment was conducted by pairing lettuce (Lactuca sativa) with mint (Mentha spicata), rucola (Diplotaxis tenuifolia), or wormwood (Artemisia absinthium) and growing them …
Tracing activation efficiency of the bio-filtration bacteria in a recirculating aquaculture system using stable isotope analysis
2016
One challenge in starting a new recirculation aquaculture system (RAS) is to find the most efficient method to activate the nitrifying bacterial biofilm in the bio-filtration system. It has been suggested that chemical startup with ammonia and nitrite surpasses the “cold start” method where biofilm originates from the fish introduced to the un-activated system. However, there is no information on how the start-up method affects the actual nitrification activity of the bio- filtration system. The objectives of this study were to evaluate how different activation techniques affect the overall function and the nitrification activity of the bio-filtration units, and the interactions between het…
Denitrifying microbial communities along a boreal stream with varying land-use
2019
Streams have an important role in regulating nitrogen (N) transportation from terrestrial ecosystems to downstream waters. Here, we examined how catchment land-use affects potential denitrification rates and the function and composition of denitrifier communities in boreal stream sediments, using stable isotope incubations and qPCR and 454-pyrosequencing targeted on nirS, nirK and nosZ genes. Although land-use influenced the water chemistry as higher nitrite + nitrate (NO x − ) concentration at the agriculture-affected sampling point, sediment organic matter content was found to be the key factor in regulating potential denitrification rates. However, the abundance as well as the diversity …