Application of (super)cavitation for the recycling of process waters in paper producing industry

In paper production industry, microbial contaminations of process waters are common and can cause damage to paper products and equipment as well as the occurrence of pathogens in the end products. Chlorine omission has led to the usage of costly reagents and products of lower mechanical quality. In this study, we have tested a rotation generator equipped with two sets of rotor and stator assemblies to generate developed cavitation (unsteady cloud shedding with pressure pulsations) or supercavitation (a steady cavity in chocked cavitation conditions) for the destruction of a persistent bacteria Bacillus subtilis. Our results showed that only supercavitation was effective and was further employed for the treatment of waters isolated from an enclosed water recycle system in a paper producing plant. The water quality was monitored and assessed according to the chemical (COD, redox potential and dissolved oxygen), physical (settleable solids, insolubles and colour intensity) and biological methods (yeasts, aerobic and anaerobic bacteria, bacterial spores and moulds). After one hour of treatment, a strong 4 logs reduction was achieved for the anaerobic sulphate reducing bacteria and for the yeastsa 3 logs reduction for the aerobic bacteriaand a 1.3 logs reduction for the heat resistant bacterial spores. A 22% reduction in COD and an increase in the redox potential (37%) were observed. Sediments were reduced by 50% and the insoluble particles by 67%. For bacterial destruction in real industrial process waters, the rotation generator of supercavitation spent 4 times less electrical energy in comparison to the previously published cavitation treatments inside the Venturi constriction design. In paper production industry, microbial contaminations of process waters are common and can cause damage to paper products and equipment as well as the occurrence of pathogens in the end products. Chlorine omission has led to the usage of costly reagents and products of lower mechanical quality. In this study, we have tested a rotation generator equipped with two sets of rotor and stator assemblies to generate developed cavitation (unsteady cloud shedding with pressure pulsations) or supercavitation (a steady cavity in chocked cavitation conditions) for the destruction of a persistent bacteria Bacillus subtilis. Our results showed that only supercavitation was effective and was further employed for the treatment of waters isolated from an enclosed water recycle system in a paper producing plant. The water quality was monitored and assessed according to the chemical (COD, redox potential and dissolved oxygen), physical (settleable solids, insolubles and colour intensity) and biological methods (yeasts, aerobic and anaerobic bacteria, bacterial spores and moulds). After one hour of treatment, a strong 4 logs reduction was achieved for the anaerobic sulphate reducing bacteria and for the yeastsa 3 logs reduction for the aerobic bacteriaand a 1.3 logs reduction for the heat resistant bacterial spores. A 22% reduction in COD and an increase in the redox potential (37%) were observed. Sediments were reduced by 50% and the insoluble particles by 67%. For bacterial destruction in real industrial process waters, the rotation generator of supercavitation spent 4 times less electrical energy in comparison to the previously published cavitation treatments inside the Venturi constriction design

Vpliv velikosti delcev organskih komunalnih odpadkov na proizvodnjo bioplina

V Sloveniji postaja problematika komunalnih odpadkov vedno bolj aktualna, saj je ravnanje z odpadki eno najslabše rešenih nalog v okviru varstva okolja. Odlaganje na deponije je trenutno najbolj običajna praksa ravnanja s komunalnimi odpadki. Posledica neprimernega ravnanja z odpadki je tudi prekomerno sproščanje metana iz odlagališč, zato bo potrebno poiskati primernejše rešitve. V tej raziskavi smo ugotavljali, kakšna je potencialna produkcija metana iz organskih komunalnih odpadkov glede na njihovo različno granulacijo (delci različnih velikosti:>100 mm, 40-100 mm, 10-40 mm in 100 mm, 40-100 mm, 10-40 mm and <10 mm). We determined volatile solids (VS), total solids (TS), total organic carbon (TOC), kjeldahl nitrogen (TKN), NH+4 and C/N ratio of the samples. Before and after incubation we determined chemical oxygen demend (COD). Following the biomethane potential test (BMP) we calculated parameters like: methane potential, methane yield and max. velocity of methane production. The results show that the particle size has the strongest influence on metan potential of organic waste and the grinding pretreatment is needed before biogas production process

Kavitacija kot potencialna tehnologija za revitalizacijo odpadnih voda: primer povečanega sproščanja hranil iz odpadnega biološkega mulja papirne industrije

Wastewater recycling and sludge removal in the paper industry account for about 60 % of all process costs. New and environmentally friendly wastewater treatment techniques are, therefore, continually being developed. Cavitation exploitation is currently a well-investigated topic that is also interesting for the paper production industry. This study investigates efficiency of hydrodynamic cavitation alone and in combination with the addition of NaOH for the treatment of secondary pulp and paper mill sludge in order to enhance nutrient release. First, two laboratory-scale devices were tested: the blow-through and the rotating hydrodynamic cavitation generator. The latter set-up proved to be more efficient: therefore, further experiments were performed on its pilot-scale version. The results showed an increase of soluble chemical oxygen demand (CODs) by 514 mg/L, total nitrogen (Nt) by 17.4 mg/L, and total phosphorous (Pt) by 2.3 mg/L. To further increase nutrient release combination of cavitation and sludge sample alkalinization was tested. The addition of NaOH and 30 min cavitation of secondary sludge (500 L) significantly improved CODs and Nt release by 2400 mg/L and 120 mg/L, respectively. Microbiological photos revealed a definite disintegration of sludge flocks. According to our estimates, 1.9 kg of released CODs from alkaline pre-treated and cavitated sludge would cost only one euro

inhibition by phenolic degradation products

In this study anaerobic digestion of selected lignocellulosic substrate, namely brewery spent (BSG), was studied. In order to facilitate anaerobic digestion several types of pretreatrment methods were tested such as: mechanical, chemical (alkali anc acid) and thermo-chemical. The anaerobic digestion experiments were carried out in asemi-continuous stirred bioreactors with the organic loading rates between 2.9 and 3.9 kgCODm-1d-1 (1.9 and 2.5 kgvss m-3d-1 respectively) and corresponding hydraulic retention times of 33-39 days. Biogas production and composition, pH, COD, TSS and VSS, short chain fatty acids and phenolic compounds were measured. A significant inhibition of biogas production occured, depending on the type of substrate pretreatment. There are indications that p-cresol is responsible for process inhibition when its concentration in the reaction mixture exceeds critical value between 115 and 240 mlL-1. Anaerobic digestion of chemically pretreated BSG (acid and alkali) and untreated-raw BSG was inhibited between the days 56 and 63 of the experiment, followed by thermo-chemically pretreated BSG on day 112 and mechanically pretreated BSG on day 126. Analyses of the substrates showed no phenolic compounds either in raw-untreated BSG or pretreated substrates, therefore the recorded p-cresol is an intermediate degradation product, responsible for process inhibition.Pivovarniške tropine so zaradi visokega bioplinskega potenciala izredno atraktivne za proces anaerobne razgradnje. Vendar pa so zaradi vsebnosti lignina težko biorazgradljive, ker nekateri produkti delujejo zaviralno na metanogene bakterije in arheje. Poskusi anaerobne razgradnje so se izvajali v polkontinuirnih pretočnih reaktorjih s popolnim premešanjem (CSTR) v mezofilnem območju (37 °C)delovni volumen reaktorjev je bil 30 litrov. Za inokulum smo uporabili sveže anaerobno metanogeno blato iz predelave prašičje gnojevke. Kot substrat smo uporabili pivovarniške tropine s 6,5 % s.s. lignina z velikostjo delcev 1-4 mm v kombinaciji s pivovarniško odpadno vodo (masno razmerje 1:2). Substrat je bil predhodno obdelan z naslednjimi tehnikami: mehanska, kemična (kisla in alkalna) in termo-kemična (kisla). V vzorcih, odvzetih iz biokemičnih reaktorjev enkrat tedensko, smo analizirali amonij, kratkoverižne maščobne kisline, kemijsko potrebo po kisiku in vsebnost aromatskih spojin. Dnevno se je izvajala meritev pH vrednosti in produkcija bioplina. Meritve produkcije bioplina so se izvajale online z merilcem pretoka bioplina ADM 2000. Opisana tehnika se je obnesla kot zelo učinkovita (povprečna proizvodnja bioplina 550 L/kg TSS), vendar pa so se po določenem času anaerobne razgradnje substrata pojavile težave z inhibicijo. Le-to pripisujemo sproščanju in kopičenju p-krezola in deloma fenola, vzporedno pa tudi ocetne in propionske kisline. Pri anaerobni razgradnji mehansko predobdelanega substrata smo zasledili pojav inhibicije pri koncentraciji p-krezola 236 mg/L, pri termo-kemičnem v mezofilnem območju pri koncentraciji 232 mg/L, pri termo-kemični v termofilnem območju pri koncentraciji 184 mg/L, pri kemični-alkalni pri koncentraciji 204 mg/L in pri kemični-kisli pri koncentraciji 115 mg/L. Ostali za inhibicijo potencialni parametri niso bili v kritičnem območju. Pri neobdelanem substratu je bil najverjetneje vzrok za inhibicijo preobremenjenost reaktorja, zaradi kopičenja nerazgrajenih velikih delcev. Na podlagi rezultatov lahko zaključimo,da je čas nastopa inhibicije produkcije bioplina iz pivovarniških tropin v CSTR reaktorju odvisen od vrste predobdelave substrata, ki vpliva na razgradnjo lignina. Noben tip predobdelave ni zagotovil stacionarnega obratovanja reaktorja v trajanju najmanj treh hidravličnih zadrževalnih časov, kar je običajni kriterij za te procese. Podani so predlogi za dodatne raziskave za doseganje tega cilja

Extraction of polyphenols and valorization of fibers from Istrian-grown pomegranate (Punica granatum L.)

Pomegranate fruit is an ancient fruit that is used not only because of its deep-red color and tasty arils but also due to the health benefits of its extracts. Pomegranate is a valuable source of bioactive compounds, including colorful anthocyanins and other polyphenols. The main objective of the present study was to gain comprehensive knowledge of the phenolic composition and antioxidative activity of a new pomegranate cultivar, grown in Northwest Istria, a part of the North Adriatic coastal area. Various parts of the pomegranate fruit parts were extracted in 70% ethanol or water. Total phenolic content and antioxidative capacity were respectively determined with Folin–Ciocalteu reagent and ABTS radical. Phenolics were examined and analyzed with TLC, LC-MS, and HPLC. Pomegranate juice was prepared from red arils and after thermal treatment, the stability of anthocyanins was monitored for several months to understand the effect of storage. The highest total phenolics were determined in ethanol pomegranate peel extracts (30.5 ± 0.6 mg GAE/g DM), and water peel extracts exhibited the highest antioxidative activity (128 ± 2 µg TE/g DM). After five months of storage of thermally treated pomegranate juice, 50–60 percentage points increase in anthocyanin degradation was observed. Pomegranate peel was further tested as a sustainable inedible food source for papermaking. Due to the low content of cellulose and the high percentage of extractives, as well as a distinguished texture and appearance, the paper made from pomegranate peel is best suited for the production of specialty papers, making it particularly interesting for bioactives recovery, followed by material restructuring