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Development of a planar electrochemical lactate biosensor
No full textJedna od aktualnih tema današnjice, kako u medicini tako i za sportsku primjenu, odnosi se na određivanje koncentracije laktata u krvi i znoju. U ovom radu naglasak je stavljen na razvoj elektrokemijskog biosenzora za laktat pri čemu se ispitivanje jedne od potencijalnih izvedbi provodilo na dvije elektrode: 3D disk elektrodi od staklastog ugljika - GCE (engl. Glassy Carbon Electrode) i plošnoj tiskanoj ugljikovoj elektrodi ED-S1PE-C2, Micrux Fluidic. Obje elektrode oslojavane su: slojem berlinskog modrila kao elektrokatalizatorom za redukciju vodikovog peroksida, enzimom laktat oksidazom kao katalizatorom za reakciju oksidacije laktata, te slojem kitozana čija je uloga bila da sigurno zadržava sloj enzima na elektrodnoj površini. Odziv pojedinačnih slojeva na elektrodama te odziv konačne, potpuno oslojene elektrode sa svim slojevima, ispitan je metodama cikličke voltametrije i kronoamperometrije. U potpunosti oslojena GC elektroda nije dala smislen odziv na laktat. Zbog neprovedene modifikacije kitozana 1 M NaOH i posljedično loše adhezije, sloj je prilikom prvog uranjanja skliznuo s elektrode. Potpuno oslojena plošna tiskana ugljikova elektroda s modificiranim slojem kitozana, ni u jednom slučaju tijekom snimanja cikličke voltametrije nije dala smislen odziv u ovisnosti o promjeni koncentracije laktata. Kronoamperometrijski odziv pokazao je uspješan odziv na laktat u koncentracijskom rasponu od 17 mM do 41 mM. Dobiveni odziv pokazao je vrlo lošu linearnost (R2 = 0,7706) i lošu osjetljivost
(-0,0572 μA/mM), što ukazuje da se vrijednost struje ne mijenja značajno s promjenom koncentracije laktata.One of the main topics currently, both in medicine and sports applications, is the determination of lactate concentration in blood and sweat.This paper focuses on the development of an electrochemical biosensor for lactate, in which the testing of one potential design was conducted on two electrodes: a 3D glassy carbon disk electrode (GCE) and a screen-printed carbon electrode (ED-S1PE-C2, Micrux Fluidic). Both electrodes were coated with layers: a Prussian blue layer as an electrocatalyst for hydrogen peroxide reduction, lactate oxidase as a catalyst for the oxidation reaction of lactate, and a chitosan layer whose role was to securely retain the enzyme layer on the electrode surface. The response of individual layers on the electrodes, as well as the response of the final, fully coated electrode with all layers, was examined using cyclic voltammetry and chronoamperometry methods. The fully coated GC electrode did not provide a meaningful response to lactate. Due to the absence of chitosan modification with 1 M NaOH and consequently poor adhesion, the layer slid off the electrode during the first immersion. The fully coated screen-printed carbon electrode with the modified chitosan layer did not, in any case, provide a meaningful response in relation to the change in lactate concentration during cyclic voltammetry recordings. The chronoamperometric response showed a successful response to lactate in the concentration range of 17 mM to 41 mM. The obtained response showed very poor linearity (R2 = 0,7706) and poor sensitivity (-0,0572 μA/mM), indicating that the current value does not significantly change with the change in lactate concentration
MXene application in electrochemical power sources
No full textOd njihovog otkrića 2011. godine MXene-i su zaniteresirali znanstvenike širom svijeta zbog njihovih izvanrednih svojstava. Njihova jedinstvena struktura od par atomskih slojeva karbida i nitrida prijelaznih metala omogućuje im veliku električnu vodljivost i veliku specifičnu površinu. Uz mnoge druge primjene ova svojstva ih čine idealnim materijalima za upotrebu u električnim izvorima energije poput litij-ionskih baterija, superkondenzatora i gorivnih članaka. U baterijama se najčešće upotrebljavaju kao anodni materijali, jer osiguravaju brzu difuziju interkalirajućih iona i stabilnosti tijekom ciklusa pražnjenja i punjenja što omogućuje povećanje kapaciteta i poboljšanje dugotrajnosti baterija. U supekondenzatorima, MXene-i povećavaju specifičnu energiju što rezultira izvorom energije s velikom specifičnom energijom i snagom. Njihova katalitička svojstva dolaze do izražaja prilikom primjene u gorivnim člancima gdje ubrzavaju reakciju redukcije kisika. Također, njihova visoka vodljivost poboljšava prijenos naboja, smanjujući unutarnji otpor uređaja. Izvanredna mehanička svojstva MXene-a iskorištena su za pretvorbu energije u triboelektričnim nanogenreatorima (TENG), a njihova biokompatibilnost iskorištena je u mikrobnim gorivnim člancima (eng. Microbial fuel cell, MFC). Navedene karakteristike čine MXene vrlo obećavajućim materijalima za budući razvoj visokoefikasnih i dugotrajnih sustava za pohranu energije, te otvaraju put prema održivoj energetskoj budućnosti.Since their discovery in 2011, MXenes have attracted attention worldwide due to their remarkable properties. Their unique structure, consisting of a few atomic layers of transition metal carbides and nitrides, grants them high electrical conductivity and a large specific surface area. Along with many other applications, these properties make them ideal materials for use in energy sources such as lithium-ion batteries, supercapacitors, and fuel cells.
In batteries, they are most commonly used as anode materials due to their ability for rapid intercalant ion diffusion and stability during charge and discharge cycles, which enhances capacity and improves battery longevity. In supercapacitors, MXenes increase specific energy resulting in a device with high specific energy and power. Their catalytic properties shine in fuel cells, where they accelerate the oxygen reduction reaction. Additionally, their high conductivity improves charge transfer, reducing the internal resistance of devices.
The exceptional mechanical properties of MXenes have been utilized for energy conversion in triboelectric nanogenerators (TENG), and their biocompatibility has been applied in microbial fuel cells (MFC). All these characteristics make MXenes highly promising materials for the future development of efficient and long-lasting energy storage systems, paving the way toward a sustainable energy future
Properties and application of fluoroelastomers
No full textFluorirani elastomeri sintetski su polimeri koji se ubrajaju u M klasu guma, tj. u gume u kojima je polimetilenski lanac zasićen. Najpoznatiji tip ovih guma fluorougljikova je guma FKM pod komercijalnim nazivom Viton. Mogu biti građene od četiri različita monomera: viniliden-fluorida (VF2), heksafluorpropilena (HFP), tetrafluoretilena (TFE) i perfluorometilviniletera (PMVE). Postoji više vrsta FKM-a ovisno o udjelu fluora, a što je njegov udio u gumi veći, veća je otpornost prema kemikalijama. Proces kojim se proizvode fluorirani elastomeri radikalska je polimerizacija u emulziji, a standardni postupci koji se koriste prilikom oblikovanja su prešanje, injekcijsko oblikovanje, ekstrudiranje i kalandriranje. Fluorirani elastomeri izrazito su stabilni pri visokim temperaturama, otporni su na plamen, starenje, ozon i oksidacijska sredstva. Posjeduju odlična mehanička svojstva koja, uz njihove ostale izvanredne karakteristike, pridonose širokoj primjeni ovih materijala. Koriste se u automobilskoj, zrakoplovnoj, kemijskoj, prehrambenoj, farmaceutskoj te naftnoj i plinskoj industriji. Njihova je glavna upotreba u proizvodnji brtvi koje mogu biti O-prstenovi, V-prstenovi, ravne ili rezane te rotacijske ili klipne brtve. Primjenjuju se i za cijevi kroz koje prolazi vruća voda, vrući zrak, u oblaganju kabela te za izolaciju. Glavni proizvođač proizvoda napravljenih od fluoriranih elastomera je DuPont.Fluoroelastomers are synthetic polymers that belong to the M class of rubbers, specifically to the rubbers where the polymethylene chain is saturated. The most well-known type of these rubbers is the fluorocarbon rubber FKM under the commercial name Viton. They can be composed of four different monomers: vinylidene fluoride (VF2), hexafluoropropylene (HFP), tetrafluoroethylene (TFE), and perfluoromethylvinylether (PMVE). There are various types of FKM depending on the fluorine content: with the higher fluorine content in the rubber, the resistance to chemicals is better. The process used to produce fluoroelastomers is radical polymerization in emulsion, and the standard methods used during shaping are pressing, injection molding, extrusion and calendering. Fluoroelastomers are extremely stable at high temperatures, resistant to flame, aging, ozone and oxidizing agents. They possess excellent mechanical properties, which, along with their other remarkable characteristics, contribute to the wide application of these materials. They are used in the automotive, aerospace, chemical, food and pharmaceutical industry as well as in the oil and gas industries. Their main use is in the production of seals, which can be O-rings, V-rings, flat or cut and rotary or piston seals. They are also used for pipes through which hot water and hot air passes, in cable insulation and for the other insulation purposes. The main manufacturer of the products made from fluoroelastomers is DuPont
Application of membrane separation processes for wastewater reuse
No full textOtpadna voda neželjeni je produkt svakog industrijskog procesa. Kako je voda veoma važan resurs, postoji potreba za njenom obradom i oporabom (ponovna upotreba). Jedna vrsta procesa koji se koriste u obradi otpadne vode su membranski separacijski procesi.
U ovome radu napisan je teorijski uvid o vrstama, karakteristikama i načinima provedbe istih. Kako se kod oporabe vode koriste tlačni membranski procesi, rad je baziran na njima.
To su mikrofiltracija (MF), ultrafiltracija (UF), nanofiltracija (NF) i reverzna osmoza (RO). Membrana, kao glavni dio ovih procesa, može biti izrađena od različitih materijala: organskih i anorganskih. Materijali se također mogu kombinirati i tako se stvaraju kompozitne membrane. Sve to omogućuje primjenu procesa pri različitim uvjetima te njihovu dobru selektivnost na određene kemijske vrste. U radu se opisuje primjena u proizvodnji pitke vode, prehrambenoj i tekstilnoj industriji te u obradi procjednih voda. Isto tako, prikazani su neki primjeri hibridnih procesa koji povezuju membranske separacijske procese s drugim procesima npr. koagulacijom i apsorpcijom.Wastewater is an undesirable byproduct of any industrial process. As water is an extremely important resource, it must be treated and reused. One process used in wastewater treatment is membrane separation process. This paper gives a theoretical overview of the types, characteristics, and implementation methods of these processes. Since pressure-driven membrane processes are used in water reuse, the paper focuses on these. These include microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO). The membrane as the main component of these processes can be made of different materials, including organic and inorganic ones. In addition, materials can be combined to produce composite membranes. As a result, the processes can be used under different conditions and offer good selectivity for specific chemical species. The paper describes applications in drinking water production, the food and textile industries, and in the treatment of landfill leachate. In addition, examples of hybrid processes are presented that combine membrane separation processes with other processes such as coagulation and adsorption
Influence of preparation conditions on the properties of poly(lactic acid) based scaffolds
No full textInženjerstvo koštanog tkiva je multidisciplinarno područje čiji je cilj razviti materijale koji će zamijeniti oštećeno tkivo te potaknuti proces zacjeljivanja kosti. Jedan od potencijalnih sustava za takvu primjenu je kompozit kitozan/hidroksiapatit (CHT/HAp). Međutim njegova loša mehanička svojstva predstavljaju glavni nedostatak za primjene u inženjerstva tkiva. Poli(mliječna kiselina) (PLA) zbog svojih dobrih mehaničkih svojstava pozitivno utječe na svojstva kompozita. Prethodna istraživanja su pokazala da prilikom razvoja sustava
PLA/CHTHAp dolazi do gubitka mase, a samim time i do značajnog gubitka mehaničkih svojstava kompozitnog materijala. Stoga, cilj ovog završnog rada je ispitati utjecaj pojedinog koraka sinteze nosača temeljenog na poli(mliječnoj kiselini). PLA uzorci izloženi su octenoj kiselini i natrijevoj lužini u više vremenskih intervala (1h, 6h, 12h, 24h i 48h), te je ispitan utjecaj liofilizacije u dva vremenska intervala (24h i 48h). Nakon svakog koraka, gravimetrijskom analizom je utvrđen gubitak mase s ciljem određivanja koraka sinteze koji najznačajnije utječe na gubitak mase, te posljedično i gubitak mehaničkih svojstava
PLA/CHT-HAp kompozita. Rezultati istraživanja su pokazali da otopina octene kiseline nema značajnog utjecaja na PLA, dok otopina natrijeve lužine ubrzava proces degradacije polimera. Uzorci podvrgnuti utjecaju lužine okarakterizirani su metodom elektronske pretražne mikroskopije (SEM) i infracrvenom spektroskopijom s Fourierovim transformacijama (FTIR).Bone tissue engineering is a multidisciplinary field aimed at developing materials that will replace damaged tissue and stimulate bone healing process. One potential system for such applications is the chitosan/hydroxyapatite (CHT/HAp) composite. Poly(lactic acid) (PLA), due to its good mechanical properties, positively affects the composites characteristic. Previous research has shown that during the development of the PLA/CHT-HAp scaffold, a certain weight loss occured and consequently, a significant loss of mechanical properties in the composite material was observed. Therefore, the goal of this experimental work is to examine the impact of individual synthesis steps on the properties of the poly(lactic acid) based scaffold. PLA samples were exposed to acetic acid and sodium hydroxide in several time intervals (1h, 6h, 12h, 24h and 48h), and the effect of lyophilization was examined for two time intervals (24h and 48h). After each step, the weight loss was determined by gravimetric analysis to identify the synthesis step that significantly affects weight loss and consequently the loss of mechanical properties of the PLA/CHT-HAp composite. The research results showed that acetic acid solution had no significant effect on PLA, while the sodium hydroxide solution accelerated the polymer degradation process. Samples subjected to the alkaline solution were characterized by scanning electron microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR)
Residence time distribution in tubular reactors
No full textTema ovog završnog rada bila je odrediti raspodjelu vremena zadržavanja u cijevnim reaktorima. Eksperiment je rađen u tri različite cijevi: praznoj cijevi, cijevi punjenoj staklenim kuglicama i spiralnoj cijevi koja je duža nego prethodne dvije cijevi. Kako bi se moglo utvrditi odstupanje promatranog sustava od idealnog određujemo raspodjelu vremena zadržavanja. Obradom eksperimentalnih podataka dobivene su različite vrijednosti vremena zadržavanja i disperzijskog broja.The topic of this final work was to determine the distributio of residence time in tubular reactor. The experiment was done in three different tubes: an empty tube, a tube filled with glass beads and a spiral tube that is longer than the previous two tubes.In order to determine the deviation of the observed system from the ideal, we determine the residence time distribution. By processing experimental data, different values of residence time and dispersion number were obtained
Removal of contaminants of emerging concern from binary solutions by membrane separation processes
No full textU današnje vrijeme novi predmet zanimanja znanstvenika postaju tzv. ''nova zagađivala'' odnosno kontaminanata koji stvaraju zabrinutost (eng. Contaminants of Emerging Concern, CEC) koja su postala veliki problem današnjice. Ovu raznoliku skupinu potencijalno opasnih spojeva čine prirodne ili sintetičke kemikalije ili mikroorganizmi kojima se do sada nije pridavalo značenje kao zagađivalima te sve većim ispuštanjem u okoliš predstavljaju potencijalnu opasnost za ekosustav. Farmaceutici i sredstva za osobnu higijenu predstavljaju jednu od najvažnijih skupina novih zagađivala. Membranski separacijski procesi pokazali su se kao učinkovite metode uklanjanja spomenutih zagađivala iz okoliša. U ovom radu provelo se ispitivanje učinkovitosti uklanjanja odabranih antibiotika (ciprofloksacin i sulfametoksazol) komercijalno dostupnim reverzno osmotskim (RO) te nanofiltracijskim (NF) membranama iz binarnih otopina. Reverzno osmotska membrana bila je XLE, a nanofiltracijske membrane NF i NF90. Najveću učinkovitost separacije pokazala je RO XLE membrana, iako ostale membrane isto pokazuju vrlo visoku učinkovitost. Mehanizam separacije farmaceutika je isključenje veličinom. Provedena je FTIR analiza ispitivanih membrana prije i poslije obrade antibiotika gdje je potvrđeno da nije došlo do interakcija.Nowadays, the ''new pollutants'', i.e., the Contaminants of Emerging Concern (CEC), which have become a major problem, are of great interest to scientists. This diverse group of potentially hazardous compounds consists of natural or synthetic chemicals or microorganisms that until now have not been considered as pollutants, and with increasing release into the environment represent a potential danger to the ecosystem. Pharmaceuticals and personal care products represent one of the most significant groups of new pollutants. Membrane separation processes have proven to be effective methods for removing these from the environment. In this research thesis, the efficacy of removal of the selected antibiotics (ciprofloxacin and sulfamethoxazole) from binary solutions by commercially available reverse osmosis (RO) and nanofiltration (NF) membranes was performed. The reverse osmosis membrane was XLE, the nanofiltration membrane was NF and NF90. The RO XLE membrane showed the highest separation efficiency, although other membranes also showed very high efficiency. The mechanism of pharmaceutical separation is based on size exclusion. FTIR analysis of the tested membranes was performed before and after treatment with antibiotics, confirming that no interactions occurred
Uklanjanje nečistoća iz pirolitičkog ulja miješanog podrijetla
No full textDemographic growth and increasing industrialization have recently affected the increased demand for fuels, so oil and fossil fuel stocks are decreasing each day, and their alternatives are being sought. Pyrolytic oil, as a product of pyrolysis, has similar composition and properties to oil. By distillation it is separated into fractions, whereby the light fraction is similar in composition to gasoline, and the medium fraction to diesel. Due to the higher concentration of impurities in pyrolytic oil, it requires pretreatment, i.e. purification. Currently, the most promising method due to its simplicity, high efficiency and economic acceptability is extraction with Deep Eutectic Solvents (DES). Accordingly, the aim of this thesis is to reduce impurities to a minimum in pyrolytic oil fractions by extraction, and also by blending purified fractions with gasoline and diesel fuel to obtain a blend (alternative fuel) of adequate characteristics, within the limits of standards for the commercial market. The effectiveness of four different DESs prepared from choline chloride, ethylene glycol, glycerol and K2CO3 was tested. The influence of three solvent to oil mass ratios (0.1:1, 0.25:1, 0.5:1) was examined using two different temperatures (room temperature and 40°C). Concentrations of nitrogen, sulphur, chlorine and total acid number were monitored. Using the Proton nuclear magnetic resonance (NMR) method, quantitative changes in the groups of olefins, paraffins and aromatics were monitored. The Fourier Transform Infrared Spectroscopy (FTIR) method confirmed the insolubility of the selected DES in the pyrolytic oil fractions. Based on the obtained results, the best DES, mass ratio and temperature were selected, and after the final purification, the fractions were blended with gasoline and diesel fuel. Finally, even though the selected blend of 97 wt.% gasoline and diesel with 3 wt.% light and medium purified pyrolytic oil fractions met the standards, the chlorine was still present in the blend, which is unacceptable for the commercial use.Demografski rast i sve veća industrijalizacija nedavno su utjecali na povećanje potražnja za gorivima, pa se zalihe nafte i fosilnih goriva svakim danom smanjuju, a traže se njihove alternative. Pirolitičko ulje, kao produkt pirolize, ima sličan sastav i svojstva kao ulje. Destilacijom se odvaja na frakcije pri čemu laka frakcija je po sastavu slična benzinu, a srednja frakcija dizelu. Zbog veće koncentracije nečistoća u pirolitičkom ulju, ono zahtijeva predtretman, tj. pročišćavanje. Trenutno, metoda koja najviše obećava zbog svoje jednostavnosti, visoke učinkovitosti i ekonomske prihvatljivosti je ekstrakcija dubokim eutektičkim otapalima (DES). Sukladno tome, cilj ovog rada je smanjiti nečistoće u pirolitičkom ulju na najmanju moguću mjeru frakcija ekstrakcijom, kao i miješanjem pročišćenih frakcija s benzinom i dizelom goriva za dobivanje mješavine (alternativnog goriva) odgovarajućih karakteristika, unutar granica standarde za komercijalno tržište. Ispitana je djelotovornost četiri različita pripremljena DES-a iz kolin klorida, etilen glikola, glicerola i K2CO3. Ispitan je utjecaj tri omjera mase otapala i ulja (0,1:1, 0,25:1, 0,5:1) na dvije različite temperature (sobna temperatura i 40°C). Praćene su koncentracije dušika, sumpora, klora i ukupni kiselinski broj. Kvantitativne promjene u skupinama olefina, parafina i aromata utvrđene su metodom nuklearne magnetske rezonancije (NMR). Metoda infracrvene spektroskopije Fourierove transformacije (FTIR) potvrdila je netopljivost odabranog DES u frakcijama pirolitičkog ulja. Na temelju dobivenih rezultata odabran je najbolji DES, omjer mase i temperature, a nakon konačnog pročišćavanja, frakcije su pomiješane s benzinom i dizel gorivom. Iako je odabrana mješavina 97 mas.% benzina i dizela s 3 mas.% laganog i srednje pročišćene frakcije pirolitičkog ulja zadovoljava standarde, klor je i dalje bio prisutan u mješavini, što je neprihvatljivo za komercijalnu upotrebu
Mechanochemistry: a green approach in preparation of pharmaceutical products with improved properties
No full textIzazovi današnjice zahtijevaju sve veću brigu za okoliš, stoga se i farmaceutska industrija susreće s novim izazovima u održivoj proizvodnji. Nekoć su farmaceutska istraživanja bila fokusirana na otkrivanje novih djelatnih tvari, dok su danas mnoga orijentirana k poboljšanju svojstva već postojećh lijekova. Dodatni izazov je razvoj novog procesa proizvodnje koji slijedi načela zelene kemije kako bi se što manje utjecalo na okoliš i razvila održiva proizvodnja. Rješenje ovih izazova nam daje mehanokemija. Za mehanokemijsku pripravu čvrstih disperzija u mlinovima nisu potrebna otapala te je moguće ovim “zelenim pristupom” proizvesti lijek poboljšanih svojstava.Care for the environment is more important than ever, which is why the pharmaceutical industry is facing new challenges in terms of sustainable production. Once, pharmaceutical research was focused on the discovery of new drugs, while today is oriented mainly on improving the properties of already existing drug products. Development of new production processes that follows the principles of green chemistry to minimise the environmental impact and develop sustainable production is a completely new challenge. Mechanochemistry offers a solution to those challenges. No solvents are needed for mechanochemical preparation of solid dispersions in mills, and it is possible using this “green approach” to produce drug product with improved properties
Fenton-based processes for removal of persistent organic pollutants
No full textPostojana organska onečišćivala predstavljaju značajan okolišni problem jer se zbog svoje postojanosti u okolišu zadržavaju dugo, a imaju naglašen potencijal štetnog djelovanja na organizme. Fentonov proces, koji uključuje generiranje veoma reaktivnih hidroksilnih radikala korištenjem vodikovog peroksida i željeza, pokazao se učinkovitim u razgradnji postojanih organskih onečišćivala. U ovom radu dane su osnove Fentonova procesa te njegovih glavnih modifikacija: foto-Fentonova procesa i Fentonu sličnih procesa. Opisani su njihovi mehanizmi i uvjeti u kojima najpovoljnije djeluju. Optimalni uvjeti za Fentonov proces uključuju niske
pH vrijednosti (oko 3) dok Fentonu slični procesi dobro djeluju i u neutralnim uvjetima.
Foto-Fentonov proces je dodatno poboljšan prisutnošću UV svjetlosti koja ubrzava generiranje radikala. Navedeni su različiti primjeri primjene ovih naprednih oksidacijskih procesa u obradi onečišćenih voda. Istaknuto je kako se pozitivno djelovanje Fentonovih procesa ne očituje samo u smanjenju koncentracije organskih onečišćivala, nego i u poboljšavaju biorazgradivost tako tretiranih voda.Persistent organic pollutants pose a significant environmental problem, as they remain in the environment for a long time due to their persistence and have a high hazard potential.
The Fenton process, which uses hydrogen peroxide and iron to generate highly reactive hydroxyl radicals, has proven to be effective in the degradation of persistent organic pollutants. This thesis presents the fundamentals of the Fenton process and its commonly used variants: the photo-Fenton process and Fenton-like processes. Their mechanisms and the conditions under which they are most efficient are described. Optimal conditions for the Fenton process are low pH values (around 3), while Fenton-like processes also work well under neutral conditions. The photo-Fenton process is enhanced by the presence of UV light, which increases the rate of radical formation. Several examples of the treatments of contaminated water by these advanced oxidation processes are given in this thesis. It has been pointed out that the positive effects of Fenton-based processes are not only in reducing the concentration of organic pollutants, but also in improving the biodegradability of such treated waters