Alicja Machnicka

Use of Hydrodynamic Disintegration to Accelerate Anaerobic Digestion of Surplus Activated Sludge

Hydrodynamic disintegration of activated sludge resulted in organic matter and polymers transfer from the solid phase into the liquid phase. Disintegration by hydrodynamic cavitation had a positive effect on the degree and rate of excess sludge anaerobic digestion. Also, addition of a part of anaerobic digested sludge containing adapted microorganisms resulted in acceleration of the process. The disruption of cells of foam microorganisms and addition to the digestion process led to an increase of biogas production.

Mesophilic-thermophilic fermentation process of waste activated sludge after hybrid disintegration.

Abstract The previously received results of individual processes of hydrodynamic and alkaline disintegration were decisive significant for the conducted research task. The combination of hydrodynamic cavitation (30 minutes duration of the process) and alkaline (pH ≈ 9) to the destruction of activated sludge caused a significant release of organic matter about 1383 mg/dm3 in comparing to individual processes. Such increase in the SCOD value resulted in a significant growth the efficiency of biogas yield in a two-stage mesophilic-thermophilic processes. The increase in yield was from 26 to 38% depending on the volume of disintegrated sludge. The effect of the two-stage fermentation resulted activated sludge hygienisation. The microbiological analysis of the influence of the fermentation with the different volume of hybrid disintegrated sludge was based on microbiological indicators: Salmonella spp. and coliphages. The obtained results prove the effectiveness of the two-stage digestion process compared to single mesophilic fermentation which not always completely eliminates the above indicators. Abstrakt Decydujące znaczenie dla przeprowadzonego zadania badawczego miały wyniki badań dotyczące jednostkowych procesów dezintegracji hydrodynamicznej i alkalizacji. Połączenie kawitacji hydrodynamicznej (30 minut trwania procesu) i alkalizacji (przy pH ≈ 9) w celu destrukcji osadu czynnego powodowało znaczące uwolnienie materii organicznej o 1383 mg/dm3 w porównaniu do jednostkowych procesów. Tak duży wzrost wartości ChZT przełożył się na istotny wzrost wydajności produkcji biogazu w procesie dwustopniowej fermentacji mezofilowo-termofilowej. Wzrost wydatku wyniósł od 26 do 38% w zależności od udziału osadu dezintegrowanego. Działanie dwustopniowej fermentacji skutkowało higienizacją osadu czynnego. Analiza mikrobiologiczna wpływu procesu fermentacji ze zróżnicowanym udziałem osadu dezintegrowanego hybrydowo została dokonana zgodnie ze wskaźnikami mikrobiologicznymi: Salmonella spp. oraz colifagi. Otrzymane wyniki świadczą o skuteczności prowadzenia procesu dwustopniowego w porównaniu z fermentacją jednostopniową mezofilową, po której nie zawsze następuje całkowita eliminacja ww. wskaźników.

Impact of Alkalization of Surplus Activated Sludge on Biogas Production

Abstract Large amounts of sludge are produced in biological wastewater treatment plants. Since the sludge is highly contaminated, it has to undergo proper stabilization before it is disposed or utilized in an environmentally safe way. On the whole, the aim of bacterial cell disintegration is the release of cell contents in the form of an aqueous extract. Chemical disintegration of surplus activated sludge by alkalization results in destruction and disruption of the flocs and microorganisms as well as increase concentration of organic matter in supernatant. The mesophilic anaerobic sewage sludge digestion is an established process, most often applied at medium and large municipal sewage treatment plants. Four major steps of anaerobic digestion are distinguished. The first hydrolysis step leads to solubilization of insoluble particulate matter and biological decomposition of organic polymers to monomers or dimers. The hydrolysis step is recognized as the rate-limiting step of the following second and third steps, the processes of acidogenesis and acetogenesis. Chemical disintegration activates biological hydrolysis and, therefore, it can significantly increase the stabilization rate of the secondary sludge. It has been shown that when the activated sludge was subjected to alkalization to pH 9.0 value, the COD concentration increased from 101 to 530 mg/dm3 in sludge supernatant. The paper presents a potential application of chemical disintegration for sewage sludge (mainly activated sludge) to upgrading biogas production. Abstrakt Osady, powstające w procesie oczyszczania ścieków, poddaje się procesom przeróbki i unieszkodliwiania w celu zmniejszenia ich objętości oraz pozbawienia ich szkodliwego wpływu na środowisko. Fermentacja metanowa jest jedną z najczęściej stosowanych metod biodegradacji materii organicznej zawartej w osadach ściekowych. W ostatnich latach odnotować można duże zainteresowanie badaczy działaniami wspomagającymi proces stabilizacji beztlenowej. Największe zainteresowanie dotyczy intensyfikacji procesu produkcji biogazu na drodze dezintegracji głównie mechanicznej, np. z wykorzystaniem ultradźwięków, homogenizacji nożowej czy też dezintegracji hydrodynamicznej. Oprócz fizycznych metod dezintegracji istnieje możliwość wykorzystania do tego celu procesów chemicznych - zakwaszania lub alkalizacji. W pracy starano się wykazać i określić wpływ jednej z metod dezintegracji - alkalizacji - osadu czynnego na proces stabilizacji beztlenowej. Dodatek substancji alkalizującej, np. wodorotlenku sodu, do osadu czynnego powoduje destrukcję kłaczków osadu oraz zmiękczanie ścian komórkowych mikroorganizmów budujących osad czynny, co w konsekwencji prowadzi do ich lizy. Uwalniana w ten sposób materia organiczna stanowi szybko i łatwo rozkładalny produkt, który w znacznym stopniu przyspiesza pierwszą fazę procesu stabilizacji beztlenowej, tj. fazę hydrolityczną. Konsekwencją tego jest przyspieszenie i wydłużenia fazy metanogennej, dzięki czemu zwiększa się ilość wyprodukowanego biogazu. Na podstawie uzyskanych wyników można wnioskować, że dezintegracja alkaliczna bardzo dobrze nadaje się do wstępnego kondycjonowania osadów. Znacznie zwiększona ilość wyprodukowanego biogazu, jak również niska cena NaOH zachęca do korzystania z tego procesu jako wstępnego przygotowania osadów przed ich stabilizacją.

Considerations of impact of Venturi effect on mesophilic digestion.

Abstract Hydrodynamic cavitation caused by the Venturi effect is one of the most promising methods of sewage sludge pre-treatment. This study has been carried out to investigate the effect of hydrodynamic cavitation on disintegration of activated sludge foam and mesophilic fermentation. Cavitation was generated in standard Venturi tube with the diameter ratio β = d0/d1 = 0.30, working at σ = 0.249. Detailed Computational Fluid Design (CFD) analysis in class of k-∈ model of internal flow has been presented. Obtained analytical investigation results confirmed the effect of strong disruption of microorganism cells and release of free organic substance into the liquid phase. After a short (30 minutes) pre-treatment, chemical oxygen demand increased by 8.63 times while Müller’s disintegration degree was 50%. Moreover, undertaken mesophilic digestion trials brought significant improvement in biogas production.

Infrared wave analysis after hydrodynamic and acoustic cavitation as effective method of confirming sewage sludge destruction.

The efficiency of disintegration of sewage sludge cells microorganisms were characterized using biochemical parameters such as COD, phosphate, ammonium nitrogen and proteins. The investigated process was additionally assessed using the coefficient DD (Degree of Disintegration). It has been demonstrated that a 30-min of hydrodynamic and ultrasonic disintegration causes the soluble COD value increased about 300 mg /L and 190 mg /L (average), while the degree of disintegration reached 24% and 21%, respectively. The efficiency of sewage sludge hydrodynamic and ultrasonic disintegration was confirmed by increased release of phosphate (V) (from 4 to 54 mg PO3− 4/L and to 50 mg PO3− 4/L, respectively), ammonium nitrogen (from 1.5 to 4 mg N-NH+ 4/L and to 3.5 mg N-NH+ 4/L, respectively) and proteins (from 5 to 70 mg/L and to 60 mg/L, respectively). The effectiveness of surplus activated sludge disintegration was tested in the infrared spectrum. Changes in absorbance at the specified wavelength attest to a release of i.e., amines, amino acids, amide groups (proteins), phosphates, ammonium salts of carboxylic acid, etc. during disintegration time. Revealing these chemical groups in over-sludge liquids attests to a destructive influence of hydrodynamic and ultrasonic cavitation on activated sludge microorganisms and effective cells lysis.

Escherichia Coli in Sewage Sludge - Detection Method / Escherichia Coli W Osadach Ściekowych - Metoda Wykrywania

Abstract Escherichia coli is Gram-negative optionally anaerobic roads which belongs to Enterobacteriaceae family. Includes in a physiological bacterial flora of human and warm-blooded animals large intestine. Escherichia coli is being met in abiotic elements of the environment so as waters, wastewater, sewage sludge, soil and the food. This bacterium is showing the pathogenicity in named terms for the peoples, triggering diseases mainly: gastrointestinal tract and urinary. Quality and quantitative proposed detections method of the bacteria E. coli contains five/six steps: - appointment dry suspended solid, - preparation averaged, test of sample and resuscitation of bacteria, - making dilutions, - enrichment and differentiation in chromogenic-selective medium, - enumerating the amount of cfu E. coli in 1 g of a dry weight, - optionally, the biochemical identification Abstrakt Escherichia coli jest Gram-negatywną, względnie beztlenową pałeczką należącą do rodziny Enterobacteriaceae. Wchodzi w skład fizjologicznej flory bakteryjnej jelita grubego człowieka oraz zwierząt stałocieplnych. Spotyka się ją w elementach abiotycznych środowiska, takich jak wody, ścieki, osady ściekowe, gleba i żywność. Bakteria ta w określonych warunkach wykazuje chorobotwórczość dla człowieka, wywołując głównie schorzenia układów pokarmowego i moczowego. Proponowana metoda jakościowa i ilościowa wykrywania bakterii E. coli zawiera pięć/sześć etapów: - oznaczenie suchej masy osadu, - przygotowanie próbki uśrednionej i badawczej oraz przywrócenie bakteriom aktywności fizjologicznej, - wykonanie rozcieńczeń, - namnażanie i identyfikacja na podłożu chromogennym-selektywnym, - wyliczenie ilości jtk E. coli w 1 g suchej masy osadu, - opcjonalnie identyfikacja biochemiczna.

FORMATION AND PROPERTIES OF DBC/PLA MICROFIBRES

In this study, a solution of dibutyrylchitin (DBC)/polylactide (PLA) blend micro and nanofibres were successfully fabricated using blends of 2,2,2-trifluoroethanol (TFE) as solvents. Fibres were produced from the solutions by electrospinning. The DBC/PLA blend solutions in various ratios were studied for electrospinning into micro/nanofibres. The morphology of the micro and nanofibres was observed by scanning electron microscope (SEM). The biggest diameters of DBC/PLA fibres were obtained for the blended microfibres in ratios of 10/90 and 25/75. The smallest diameter was observed for pure polymers. The antibacterial properties were examined for materials obtained by electrospinning. In the experiments, materials with antibacterial properties were made. It is likely that the electrospun micro and nanofibres will be used in the native extracellular matrix for tissue engineering.

Disintegration as a key-step in pre-treatment of surplus activated sludge

This study has been carried out to investigate the effect of microwave, alkalization and freezing on surplus activated sludge disintegration (release of organic/inorganic substances into the supernatant) and mesophilic fermentation. After applying pre-treatments, chemical oxygen demand increased by 7–35 times, disintegration degree was 35–47%, proteins by 5–25, carbohydrates by 2–3, phosphates 7–22 and ammonium by 3–16 times. Disintegration by microwave, alkalization and freezing has a positive effect on the rate of sludge anaerobic digestion. Biogas production increased by: 62; 49 and 58%, for microwave radiation, alkalization and freezing, respectively. The conducted research shows that the application of disintegration as a pre-treatment of surplus activated sludge is an effective method, allowing for practical using sewage sludge.

Investigation of the effectiveness of nutrient release from sludge foam after hybrid pretreatment processes by IR analysis and EDX Quantification

ABSTRACT One of the problems in wastewater treatment technologies is the formation of foam/scum. It is thought that filamentous microorganisms are responsible for foam formation and foam elimination/destruction can be carried out by various methods, among which disintegration is included. Hybrid disintegration (chemical decomposition and hydrodynamic cavitation) of foam microorganisms results in the transfer of phosphates, ammonium nitrogen, magnesium and potassium from the foam solids into the liquid phase. Application of both methods as a hybrid pretreatment process caused an increase in the concentration of phosphates of about 650 mg  L−1 and ammonium nitrogen of about 30 mg  L−1. The concentration of Mg2+ and K+ in the solution increased from 6.8 and 26.1 mg Mg2+ L−1 to 32.2 and 82.2 mg K+ L−1, respectively. The presence of nutrients and metal cations in the solid phase of foam was acknowledged by EDX Quantification. The confirmation of physico-chemical changes and release of cellular matter as a result of cellular lysis (hybrid disintegration) was done by infrared analysis. It was demonstrated that the disintegration of foam permits the removal of a part of nutrients in the form of struvite.

Efficiency of biological phosphorus removal by filamentous bacteria

Abstract Phosphorus removal in wastewater treatment plant is carried out by chemical precipitation, advanced biological treatment or a combination of both. One of the biggest problems with high concentration of phosphorus in water environment is eutrophication. Activated sludge flocs have a heterogeneous structure, which consist of a variety of microorganisms. Filamentous bacteria are normally present in the activated sludge and have ability to assimilation of phosphorus. In this study phosphorus accumulation by isolated filamentous bacteria from activated sludge foam was present.