3 research outputs found
Structure and diversity of nitrifying microbial community in biofilm
No full textV procesu čiščenja odpadne vode na čistilnih napravah je proces nitrifikacije ključen za odstranjevanje enega od najpomembnejših hranil-dušika- z nitrifikacijskimi bakterijami. Spremljali smo proces nitrifikacije ter prisotnost, pestrost in stabilnost mikrobnih združb na osnovi zaporedij 16S rRNA in specifičnih funkcionalnih genov (npr. amoA) v industrijskih in laboratorijskih reaktorjih z imobilizirano biokulturo. Zanimalo nas je predvsem kako se združba nitrifikacijskih bakterij v imobilizirani biokulturi ali biofilmu na prosto plavajočih plastičnih nosilnih elementih Kaldnes v biofilmu odziva glede na različno kvaliteto odpadne vode ter letni čas. Mikrobno združbo na CČN Domžale-Kamnik (CČN DK) smo analizirali z metodo TRFLP in s sekvenciranjem genov za 16S rRNA in genov amoA. Z analizo TRFLP smo ugotovili, da se je, kljub nihanju strukture združbe v času, vzpostavila določena razlika med vzorci iz pilotnih sistemov z mehansko čiščeno in sintetično odpadno vodo, sama velikost (industrijski vs. mini reaktor) sistema pa ni bila pomembna. Še bolj očitna razlika med združbami, ki so bile izpostavljene različnim odpadnim vodam, se je pokazala z analizo funkcionalnega nitrifikacijskega gena amoA. In sicer so se zunanji industrijski reaktor in mini pilotni reaktorji, obremenjeni z mehansko čiščeno odpadno vodo, razlikovali tako po sestavi kot po pestrosti nitrifikacijskih mikroorganizmov. Pestrost splošne 16S rRNA mikrobne združbe je bila višja v reaktorjih z mehansko čiščeno odpadno vodo, medtem ko so reaktorji z sintetično odpadno vodo imeli večjo pestrost nitrifikacijske (amoA) mikrobne združbe. Na podlagi rezultatov sklepamo, da ima kvaliteta odpadne vode večji vpliv na sestavo združbe kot pa dejavniki okolja kot sta temperatura ali pa velikost reaktorjev.In the process of treating waste water in biological treatment plants, the nitrification process is crucial for the removal of one of the most important nutrients, i.e. nitrogen, using nitrification bacteria. The aim of our work was to produce a study of the process of nitrification itself, including an analysis of the presence, diversity and stability of microbial communities based on the 16S rRNA sequences and specific functional genes (eg. amoA) in industrial-scale and laboratory-scale reactors with immobilized bioculture. Industrial-scale reactors treat wastewater of temporary variable composition under different weather conditions, while the microbial population of wastewater treatment plants are often studied in controlled laboratory-scale systems with defined influent at a constant temperature. 16S rRNA and ammonia oxidising amoA-gene-defined bacterial community structure was investigated in industrial-scale and laboratory-scale moving bes biofilm reactor (MBBR) treating municipial wastewater or synthetic ammonium solition. Nitrification activity, 16S rRNA and amoA gene TRFLP profiles were comparable between industrial and laboratory-scale reactors with municipial wastewater. Reactors with synthetic ammonium solution exhibited higher nitrification and higher relative abundance of Nitrosomonadaceae and Nitrospiraceae families but only small changes in general bacterial community structure was detected compared to MBBR reactors treating municipial wastewater. Nitrosomonas europea lineage dominated in reactors treating municipial wastewater, whilu uncultivated Nitrosomonas-like sequences prevailed in reactors with synthetic ammonia solution. These results suggest that influent type has a stronger influence on community structure than operational conditions, such as temperature or reactor size
Integral analysis of hydrodynamic cavitation effects on waste activated sludge characteristics, potentially toxic metals, microorganisms and identification of microplastics
No full textWastewater treatment plants, the last barrier between ever-increasing human activities and the environment, produce huge amounts, of unwanted semi-solid by-product - waste activated sludge. Anaerobic digestion can be used to reduce the amount of sludge. However, the process needs extensive modernisation and refinement to realize its full potential. This can be achieved by using efficient pre-treatment processes that result in high sludge disintegration and solubilization. To this end, we investigated the efficiency of a novel pinned disc rotational generator of hydrodynamic cavitation. The results of physical and chemical evaluation showed a reduction in mean particle size up to 88%, an increase in specific surface area up to 300% and an increase in soluble COD, NH-N, NO-N, PO-P up to 155.8, 126.3, 250 and 29.7%, respectively. Microscopic images confirmed flocs disruption and damage to yeast cells and Epistilys species due to mechanical effects of cavitation such as microjets and shear forces. The observed cell ruptures and cracks were sufficient for the release of small soluble biologically relevant dissolved organic molecules into the bulk liquid, but not for the release of microbial DNA. Cavitation treatment also decreased total Pb concentrations by 70%, which was attributed to the reactions triggered by the chemical effects of cavitation. Additionally, the study confirmed the presence of microplastic particles and fibers of polyethylene, polyethylene terephthalate, polypropylene, and nylon 6 in the waste activated sludge
The use of hydrodynamic cavitation for waste-to-energy approach to enhance methane production from waste activated sludge
No full textAnaerobic digestion in wastewater treatment plants converts its unwanted end product – waste activated sludge into biogas. Even if the process is well established, pre-treatment of the sludge can further improve its efficiency. In this study, four treatment regimes for increasing methane production through prior sludge disintegration were investigated using lab-scale cavitation generator and real sludge samples. Three different cavitating (attached cavitation regime, developed cloud shedding cavitation regime and cavitation in a wake regime) and one non-cavitating regime at elevated static pressure were studied in detail for their effectiveness on physical and chemical properties of sludge samples. Volume-weighted mean diameter D[4,3] of sludge\u27s particles decreased by up to 92%, specific surface area increased by up to 611%, while viscosity (at a shear rate of 3.0 s) increased by up to 39% in the non-cavitating and decreased by up to 24% in all three cavitating regimes. Chemical changes were more pronounced in cavitating regimes, where released soluble chemical oxygen demand (sCOD) and increase of dissolved organic matter (DOM) compounds by up to 175% and 122% were achieved, respectively. Methane production increased in all four cases, with the highest increase of 70% corresponding to 312 mL CH g COD. However, this treatment was not particularly efficient in terms of energy consumption. The best energy balance was found for the regime with a biochemical methane potential increase of 43%
