Stanisław Wacławek

Simple spectrophotometric determination of monopersulfate.

A simple, sensitive and accurate spectrophotometric method has been developed and validated for the determination of monopersulfate (MPS) which is an active part of potassium monopersulfate triple salt that has the commercial name - Oxone. This work proposes a spectrophotometric determination of monopersulfate based on modification of the iodometric titration method. The analysis of absorption spectra was made for the concentration range from 1.35 to 13.01 ppm of MPS (with a detection and quantification limit of 0.41 and 1.35 ppm, respectively) and different pH values. The influence of several anions on the measurement was also investigated. Furthermore, the absorbance of iron and cobalt (often used as free radical initiators) proved to have no effect on the measurement of MPS concentrations. On the basis of the conducted studies, we propose 395 nm as an optimal wavelength for the determination of MPS concentrations.

The impact of peroxydisulphate and peroxymonosulphate on disintegration and settleability of activated sludge.

ABSTRACT Chemical treatment processes have mostly been considered as an efficient way for biosolid minimization. The improvement of sludge dewatering was more a welcome side-effect of these sequential processes. In this study, heat-activated sodium peroxydisulphate (PDS) and potassium peroxymonosulphate (MPS) were applied in order to disintegrate waste activated sludge (WAS). PDS and MPS treatment of WAS results in the polymer transfer of organic matter from the solid phase to the liquid phase. Our research work was done for chemical disintegration of WAS by PDS and MPS in doses of 0.2%, 0.4%, 0.6%, 0.8% and 1% (169.5, 339.0, 508.5, 678.0 and 847.5 mg ) activated at temperatures of 60°C and 90°C for 30 min. The application of these methods causes the soluble chemical oxygen demand value to increase in the supernatant. In addition, there was a positive influence on the sludge volume index which decreased for the highest doses of PDS of over 63% and 77% and MPS of over 78% and 82% through heat activation at temperatures of 60°C and 90°C, respectively. Furthermore, MPS was more successful in the floc particle destruction, therefore it caused a higher sludge settlement acceleration (sedimentation/compaction speed) than PDS. The experimental results demonstrated that the application of heat-activated PDS and MPS may become a novel effective way of processing sewage sludge.

Gum karaya (Sterculia urens) stabilized zero-valent iron nanoparticles: characterization and applications for the removal of chromium and volatile organic pollutants from water

This paper illustrates a method for the stabilization of nanoscale zerovalent iron (NZVI) suspensions with a “green” biopolymer, Gum Karaya (GK). The stability, sedimentation, aggregation behavior and reactivity towards Cr(VI) and volatile organic compounds using NZVI–GK (GK stabilized NZVI) and bare NZVI, were assessed. The stabilization mechanism of NZVI–GK was demonstrated using ATR-FTIR, XRD, XPS, TEM, SEM, TGA and particle size analysis. The NZVI–GK nanoparticle suspension was found to be stable for at least three months, suggesting a superior stability rendering property of GK which forms a scaffold to prevent NZVI from aggregating. Batch experiments, centred on Cr(VI) reduction and degradation of volatile organic compounds, confirmed that NZVI–GK was more reactive than bare NZVI. Furthermore, XPS and ICP-MS results revealed that Cr(VI) was reduced to Cr(III) by NZVI–GK and the remaining Cr(III) in solution was adsorbed onto GK, thereby completely removing chromium from the contaminated water. Our study suggests that an important role is played due to the attributes of GK (which include non-toxicity, biodegradability and cost-effectiveness) in conjunction with the ability of NZVI to remove all chromium viz. [Cr(VI) and Cr(III)] coupled with the total degradation and removal of VOCs (cis-1,2-dichloroethene, perchloroethene and trichloroethene) from water.

Green Synthesis: Nanoparticles and Nanofibres Based on Tree Gums for Environmental Applications

Abstract The recent advances and potential applications of nanoparticles and nanofibres for energy, water, food, biotechnology, the environment, and medicine have immensely conversed. The present review describes a ‘green’ method for the synthesis and stabilization of nanoparticles and ‘green electrospinning’ both using tree gums (arabic, tragacanth, karaya and kondagogu). Furthermore, this review focuses on the impending applications of both gum stabilized nanoparticles and functionalized membranes in remediation of toxic metals, radioactive effluents, and the adsorptive removal of nanoparticulates from aqueous environments as well as from industrial effluents. Besides, the antibacterial properties of gum derivatives, gum stabilized nanoparticles, and functionalized electrospun nanofibrous membranes will also be highlighted. The functionalities of nanofibrous membranes that can be enhanced by various plasma treatments (oxygen and methane, respectively) will also be emphasized.

Impact of peroxydisulphate on disintegration and sedimentation properties of municipal wastewater activated sludge

In the study, a thermally activated sodium peroxydisulphate (PDS; Na2S2O8) was applied in order to disintegrate wastewater activated sludge (WAS). Chemical disintegration of WAS results in organic matter and polymer transfer from the solid phase to the liquid phase. Soluble chemical oxygen demand (SCOD) is often used to characterise the disintegration efficiency of WAS flocs and microorganisms cells. The present study was conducted in order to chemically disintegrate WAS using PDS in doses of 0.2 %, 0.4 %, 0.6 %, 0.8 % and 1.0 % activated at temperatures of 50°C, 70°C and 90°C for 30 min. The temperature rise induced the PDS to form free radicals, which resulted in an increase in SCOD, i.e. for the highest dose of PDS, the SCOD value attained 2140 mg dm−3 (almost a 15-fold increase over the WAS value). A further positive effect from using this method was a decrease in the sludge volume index (SVI) from 89.8 cm3 g−1 to 30.6 cm3 g−1. On the basis of the results obtained, it may be concluded that thermally activated PDS is suitable for disintegration and has a positive impact on WAS sedimentation properties.

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.

Electrospun fibers based on Arabic, karaya and kondagogu gums

Nanofibers of natural tree polysaccharides based on three gums namely Arabic (GA), karaya (GK) and kondagogu (KG) have been prepared for the first time using electrospinning. Electrospinning solutions were prepared by mixing gum solutions of GA, GK & KG with eco-friendly polymers such as polyvinyl alcohol (PVA) or polyethylene oxide (PEO). The present study focuses on the effect of electrospinning blended solutions of GA, GK or KG with PVA or PEO, additives which influence system parameters and process parameters. This has important effects on the electrospinning process and the resulting fibers whose morphology and physicochemical properties were evaluated. The mass ratios of 70:30 to 90:10 for PVA: GA, PVA: GK and PVA: KG were observed to establish an optimum blend solution ratio in order to fabricate uniform beadless nanofibers with an average diameter of 240±50, 220±40 and 210±30nm, respectively. Various structural and physicochemical properties of the electrospun fibers were investigated. Furthermore, the comparisons of various functionalities of the untreated and plasma treated electrospun fibers were assessed. The methane plasma treated nanofibers were shown to be of extremely specific surface area, improved water contact angle, high surface porosity and roughness and superior hydrophobic properties compared to untreated fibers.

Use of Various Zero Valent Irons for Degradation of Chlorinated Ethenes and Ethanes

Abstract Amongst all of the reducing agents that can be used in environmental remediation, zero valent iron (ZVI) is one of the most common due to its environmental acceptance, high reaction rate, good availability, and long-term stability. Moreover, ZVI mobility, stability and reactivity can be enhanced by the application of a DC electric current, ie electrokinetics (EK). In the study, six various slurries containing different ZVI were tested for their efficacy for chlorinated ethenes and ethanes degradation. Chlorinated compound concentrations, pH, oxidation-reduction potential (ORP) and conductivity were determined during the long-term kinetic test. Kinetic rate constants calculated for the degradation of three chlorinated ethenes (PCE, TCE and cis-DCE) concluded that EK brings substantial contribution to chlorinated compounds degradation. Nano-scale zero valent iron STAR had the highest reaction rates compare to the other ZVI tested. The performed study could serve as a preliminary assessment of various available ZVI before in-situ application.

The Impact of Oxone on Disintegration and Dewaterability of Waste Activated Sludge.

Biochemical parameters such as soluble chemical oxygen demand (SCOD), phosphate, ammonium nitrogen and proteins are often used to characterize the efficiency of disintegration of waste activated sludge (WAS) flocs and microorganism cells. In this study, the chemical disintegration using peroxymonosulfate (MPS, Oxone) and thermally activated MPS, were evaluated for the destruction of WAS. Our study was conducted for chemical disintegration of WAS by MPS in doses between 84.7 - 847.5 mg/g(TS) activated by temperatures of 50, 70 and 90 °C over 30 minutes. The application of these methods causes an increase in the soluble COD value and protein concentration in the supernatant. Also, they positively influence the sludge volume index (SVI) which decreased from 89.8 to 17.2 ml/g. Our research work confirmed that the application of thermally activated MPS may become a new effective way of improving sewage treatment and sewage sludge processing.