Municipal Wastewater Reclamation and Water Reuse for Irrigation by Membrane Processes

Municipal wastewater was treated by membrane bioreactor (MBR), and the obtained MBR effluent was then treated by reverse osmosis (RO), and nanofiltration (NF). The MBR effluent was additionally treated by reverse osmosis (XLE) and nanofiltration (NF90 and NF270) membranes. RO and NF permeate output streams were assessed for their utilization in agricultural irrigation. The MBR used a hollow fiber ZeeWeed 1 ultrafiltration membrane. Conductivity, turbidity, total suspended solids, chemical oxygen demand, and dissolved organic carbon were rejected by MBR with average values of 10 %, 100 %, 99.8 %, 96 %, and 88 %, respectively. Further treatment with RO/NF membranes showed additional reduction in all measured parameters. According to results, MBR effluent belongs to the ‘slight to moderate’ degree of restriction on use due to conductivity, chloride, and sodium concentrations. RO/NF permeate, based on all parameters, belongs to the ‘none’ degree of restriction on use, except on sodium adsorption ratio (SAR), where it belongs to the ‘severe’ degree of restriction on use. Based on conductivity and SAR parameters, assessment of produced water quality obtained by blending of two effluents (50 % of MBR and 50 % of NF270 permeate) resulted in an output stream appropriate for irrigation, proving that the blending of output streams in this ratio is a good strategy for agricultural irrigation

Optimization of biodiesel production process from waste oil by using new guanidine catalysts

Kako bi se unaprijedila proizvodnja biodizela s ekonomskog i ekološkog gledišta potrebno je istražiti primjenu novih katalizatora, ekološki prihvatljivijih i ekonomski isplativijih sirovina te optimirati proces s istima. Konvencionalni katalizatori poput NaOH i KOH kada se primjenjuju na biljna ulja s većim sadržajem slobodnih masnih kiselina i vode dovode do saponifikacije koja bitno otežava separaciju produkata i povećava proizvodnju otpadne vode. U isto vrijeme primjena biljnih ulja (posebice jestivih) negativno utječe na tržište hrane te smanjuje količinu iskoristivih poljoprivrednih površina. Osim toga, najčešće korišteni alkohol za transesterifikaciju, metanol, proizvodi se iz neobnovljivih izvora (povećava emisiju stakleničkih plinova) i toksičan je. Iz tih razloga u ovom radu ispitana je aktivnost novog gvanidinskog katalizatora N,N',N''-tris(3-dimetilamino)propil gvanidina (GV3) uz kojeg ne dolazi do saponifikacije, a kao sirovine korištene su otpadno restoransko ulje i niži alkoholi, metanol, etanol, n-butanol i i-butanol. Ovdje je posebice zanimljiva sirovina etanol kojeg je moguće proizvesti iz obnovljivih izvora (bioetanol). Shodno tome provedeno je modeliranje i optimizacija šaržnog procesa proizvodnje etilnih estera višemasnih kiselina (FAEE) transesterifikacijom otpadnih ulja s etanolom pomoću GV3 za najvažnije procesne parametre (maseni udio katalizatora, molarni omjer etanola i otpadnog ulja, temperatura i vrijeme provedbe reakcije) metodom planiranja pokusa s faktorskim centralno kompozitnim planom. Kao rezultat razvijen je vjerodostojan empirijski matematički model. Pomoću metode odzivnih površina (RSM) utvrđeni su optimalni uvjeti procesa za zadane ciljeve. Ciljevi optimiranja bili su postizanje maksimalne konverzije uz minimalan udio katalizatora i minimalnu temperaturu s omjerom reaktanata što bližim stehiometrijskom te što kraćem vremenu. Ovisno o zadanoj važnosti pojedinog cilja dobiveni su različiti optimalni uvjeti od kojih su odabrani: maseni udio katalizatora od 1,72 mas. %; molarni omjer etanola i otpadnog ulja od 5,35:1; temperatura od 40 °C i vrijeme od 40 min s predviđenom konverzijom od 91,44 %.In order to improve the production of biodiesel from an economic and environmental point of view, it is necessary to research the application of new catalysts, environmentally friendlier and cost-effective raw materials and their process optimization. Conventional catalysts, i.e. NaOH and KOH, when applied to vegetable oils with higher content of free fatty acids and water, usually lead to saponification. The resulting soap makes the separation of products difficult and thus increase waste water production. Furthermore, the use of edible vegetable oils has a negative impact on the food market by reducing the quantity of available farmland and increasing the price of food. Methanol is the most commonly used alcohol for transesterification. But it is toxic and produced from non-renewable sources, increasing greenhouse gas emissions. For this reason, the activity of the new guanidine catalyst N,N',N''-tris(3-dimethylaminopropyl)-guanidine (GV3) for the tansesterification of waste oil with various lower alcohols (methanol, ethanol, n-butanol and i-butanol) were examined. Ethanol is particularly interesting as a raw material because it can be produced from renewable sources, i.e. bioethanol. The process optimization with ethanol and waste oil was carried out for the most important process parameters (mass fraction of the catalyst, the molar ratio of ethanol and waste oil, reaction temperature and time) in accordance with the factorial central composite design of experiments. As result the significant empirical mathematical model was developed. Using Response Surface Methodology (RSM) optimal conditions were determined for the tested parameters. The goals of the optimization were to maximize the conversion, minimize the mass fraction of catalyst, at the lowest temperature and the shortest reaction time with the molar ratio of ethanol and waste oil closer to stechiometric. Depending on the importance given to a individual goal, different optimal conditions were calculated. The chosen optimal conditions were: the catalyst mass fraction of 1.72 wt.%; the molar ratio of ethanol and the waste oil 5.35:1; reaction time of 80 min at 40 °C with the calculated conversion of 91.44 %

Optimization of biodiesel production process from waste oil by using new guanidine catalysts

Kako bi se unaprijedila proizvodnja biodizela s ekonomskog i ekološkog gledišta potrebno je istražiti primjenu novih katalizatora, ekološki prihvatljivijih i ekonomski isplativijih sirovina te optimirati proces s istima. Konvencionalni katalizatori poput NaOH i KOH kada se primjenjuju na biljna ulja s većim sadržajem slobodnih masnih kiselina i vode dovode do saponifikacije koja bitno otežava separaciju produkata i povećava proizvodnju otpadne vode. U isto vrijeme primjena biljnih ulja (posebice jestivih) negativno utječe na tržište hrane te smanjuje količinu iskoristivih poljoprivrednih površina. Osim toga, najčešće korišteni alkohol za transesterifikaciju, metanol, proizvodi se iz neobnovljivih izvora (povećava emisiju stakleničkih plinova) i toksičan je. Iz tih razloga u ovom radu ispitana je aktivnost novog gvanidinskog katalizatora N,N',N''-tris(3-dimetilamino)propil gvanidina (GV3) uz kojeg ne dolazi do saponifikacije, a kao sirovine korištene su otpadno restoransko ulje i niži alkoholi, metanol, etanol, n-butanol i i-butanol. Ovdje je posebice zanimljiva sirovina etanol kojeg je moguće proizvesti iz obnovljivih izvora (bioetanol). Shodno tome provedeno je modeliranje i optimizacija šaržnog procesa proizvodnje etilnih estera višemasnih kiselina (FAEE) transesterifikacijom otpadnih ulja s etanolom pomoću GV3 za najvažnije procesne parametre (maseni udio katalizatora, molarni omjer etanola i otpadnog ulja, temperatura i vrijeme provedbe reakcije) metodom planiranja pokusa s faktorskim centralno kompozitnim planom. Kao rezultat razvijen je vjerodostojan empirijski matematički model. Pomoću metode odzivnih površina (RSM) utvrđeni su optimalni uvjeti procesa za zadane ciljeve. Ciljevi optimiranja bili su postizanje maksimalne konverzije uz minimalan udio katalizatora i minimalnu temperaturu s omjerom reaktanata što bližim stehiometrijskom te što kraćem vremenu. Ovisno o zadanoj važnosti pojedinog cilja dobiveni su različiti optimalni uvjeti od kojih su odabrani: maseni udio katalizatora od 1,72 mas. %; molarni omjer etanola i otpadnog ulja od 5,35:1; temperatura od 40 °C i vrijeme od 40 min s predviđenom konverzijom od 91,44 %.In order to improve the production of biodiesel from an economic and environmental point of view, it is necessary to research the application of new catalysts, environmentally friendlier and cost-effective raw materials and their process optimization. Conventional catalysts, i.e. NaOH and KOH, when applied to vegetable oils with higher content of free fatty acids and water, usually lead to saponification. The resulting soap makes the separation of products difficult and thus increase waste water production. Furthermore, the use of edible vegetable oils has a negative impact on the food market by reducing the quantity of available farmland and increasing the price of food. Methanol is the most commonly used alcohol for transesterification. But it is toxic and produced from non-renewable sources, increasing greenhouse gas emissions. For this reason, the activity of the new guanidine catalyst N,N',N''-tris(3-dimethylaminopropyl)-guanidine (GV3) for the tansesterification of waste oil with various lower alcohols (methanol, ethanol, n-butanol and i-butanol) were examined. Ethanol is particularly interesting as a raw material because it can be produced from renewable sources, i.e. bioethanol. The process optimization with ethanol and waste oil was carried out for the most important process parameters (mass fraction of the catalyst, the molar ratio of ethanol and waste oil, reaction temperature and time) in accordance with the factorial central composite design of experiments. As result the significant empirical mathematical model was developed. Using Response Surface Methodology (RSM) optimal conditions were determined for the tested parameters. The goals of the optimization were to maximize the conversion, minimize the mass fraction of catalyst, at the lowest temperature and the shortest reaction time with the molar ratio of ethanol and waste oil closer to stechiometric. Depending on the importance given to a individual goal, different optimal conditions were calculated. The chosen optimal conditions were: the catalyst mass fraction of 1.72 wt.%; the molar ratio of ethanol and the waste oil 5.35:1; reaction time of 80 min at 40 °C with the calculated conversion of 91.44 %

Treatment of Municipal Wastewater by Membrane Processes

Industrijalizacija, porast populacije i urbanizacija glavni su uzroci stvaranja sve većih količina komunalnih otpadnih voda (KOV) koje, neobrađene, predstavljaju ozbiljnu prijetnju prirodnim vodonosnicima. Radi zaštite okoliša i prirodnih resursa potrebno je primjenjivati visokoučinkovite i okolišu naklonjene tehnologije obrade KOV-a. Cilj ovog rada bio je obrada KOV-a naprednim membranskim postupcima; membranskim bioreaktorom (MBR) te dodatnom obradom MBR efluenta s nanofiltracijom (NF) i reverznom osmozom (RO). Laboratorijska i pilot-obrada KOV-a MBR-om rezultirala je smanjenjem kemijske potrošnje kisika (KPK), biokemijske potrošnje kisika (BPK5), mutnoće i suspendiranih tvari za više od 92 %. Mikrobiološki parametri smanjeni su za 4,12 log10 do 4,88 log10. Naknadna obrada MBR efluenta s RO/NF membranama (XLE i NF270) pokazala je dodatno smanjenje svih mjerenih parametara. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.Industrialization, population growth, and urbanization are the main causes for the generation of increasing quantities of municipal wastewater (MWW) which, untreated, pose a serious threat to natural aquifers. In order to protect the environment and natural resources, it is necessary to use high-efficiency and environmentally friendly technologies for the treatment of MWW. The goal of this work was treatment of MWW with advanced membrane processes; membrane bioreactor (MBR) and nanofiltration (NF) and reverse osmosis (RO). Laboratory and pilot treatment of MWW with MBR resulted in a reduction of more than 92 % in chemical oxygen demand (COD), biochemical oxygen demand (BOD5), turbidity and suspended matter. The number of microbiological parameters decreased by 4.12 log10 to 4.88 log10. Subsequent treatment of MBR effluent with RO/NF membranes (XLE and NF270) further reduced all measured parameters. This work is licensed under a Creative Commons Attribution 4.0 International License

Application of membrane processes for treatment and reuse of rendering plant wastewater

Postrojenja za obradu životinjskih nusproizvoda (POŽN) ispunjavaju važnu ulogu u održivosti mesne industrije obradom nastalih nusproizvoda (opasnog otpada) te tako smanjuju negativan utjecaj mesne industrije na okoliš i ljudsko zdravlje. Tijekom obrade ovakve vrste opasnog otpada dolazi do potrošnje velike količine vode i proizvodnje veoma opterećene otpadne vode. Kako bi se riješili navedeni problemi, u ovom radu ispitana je primjena tlačnih membranskih postupaka ultrafiltracije (UF), nanofiltracije (NF) i reverzne osmoze (RO) za obradu i oporabu sekundarnog efluenta biološke obrade otpadne vode POŽN-a. POŽN zbog velike opterećenosti otpadne vode u sklopu postrojenja mora imati sustav za obradu otpadne vode. Otpadna voda POŽN-a ima povoljan omjer BPK/KPK što takvu vodu čini prikladnom za biološku obradu. Stoga se u ovom radu nije istraživala izravna obrada otpadne vode već njezin sekundarni efluent dobiven nakon biološke obrade. Ispitana je učinkovitost obrade primjenom komercijalnih ravnih UF membrana (MW, GM, CQ, GK, PT, PU i PW) i UF membrane u obliku šupljih vlakana (ZW-1) te ravnih NF/RO membrana (NF270, NF, NF90 i XLE). Za utvrđivanje učinkovitosti obrade praćeni su sljedeći parametri: električna provodnost (κ), mutnoća, sadržaj ugljika (ukupni ugljik – TC, anorganski ugljik – IC i otopljeni organski ugljik – DOC), kemijska potrošnja kisika (KPK), ukupni Kjeldahlov dušik (TKN), sadržaj aniona (Cl-, F-, NO2-, NO3-, PO43-, SO42- i Br-) i kationa (Na+, Ca2+, Mg2+, K+, NH4+ i Li+) i pH. UF membrane pokazale su sličan učinak separacije, a to uključuje učinkovito smanjenje mutnoće i KPK-a te uklanjanje DOC-a, ali loše zadržavanje dušika i soli. S druge strane, RO i NF membrane znatno su bolje zadržale dušik i otopljene soli, ali njihova učinkovitost je uvelike ovisila o primijenjenoj membrani. Radi usporedbe, čiste i korištene membrane okarakterizirane su infracrvenom spektroskopijom s Fourierovom transformacijom (FTIR) i skenirajućim elektronskim mikroskopom (SEM). Blokiranje membrana modelirano je primjenom modificiranih Hermijinih modela za četiri mehanizma blokiranja (potpuno blokiranje pora, djelomično blokiranje pora, unutarnje blokiranje pora i nastajanje kolača). Površine membrane okarakterizirane su goniometrom u svrhu određivanja hidrofilnosti membrana preko kontaktnog kuta vode. Ispitan je utjecaj predobrade sekundarnog efluenta nakon biološke obrade na blokiranje UF i NF membrana pješčanom filtracijom i kombinacijom koagulacije i pješčane filtracije te UF kao predobrade za NF i RO membrane. Pješčana filtracija nije se pokazala uspješnom u suzbijanju blokiranja UF i NF membrana. Koagulacija je optimirana s aspekta odabira najpogodnijeg koagulacijskog sredstva (FeCl3, Al2(SO4)3, Aquaklar A (10 % Al2O3) i Aquaklar C (18 % Al2O3)) i radnih uvjeta (pH vrijednost i koncentracija koagulacijskog sredstva). Pokazalo se da je najprikladnije koagulacijsko sredstvo FeCl3 pri pH vrijednosti 5,87 i koncentraciji 10 mg Fe3+ L^-1. Koagulacija pri optimalnim uvjetima i naknadna pješčana filtracija dokazale su se kao uspješna predobrada pri čemu je pad fluksa kod UF membrana smanjen za 50 – 95 %, a za NF membrane 76 – 95 %. S druge strane, primjenom UF s MW membranom kao predobradom za NF i RO smanjen je pad fluksa za 50 – 72 %, a predobradom sa ZW-1 membranom za 2 – 67 %. Ispitano je i kemijsko čišćenje UF membrana blokiranih tijekom obrade sekundarnog efluenta POŽN-a s dva sredstva (PermaClean 99 – alkalno sredstvo i PermaClean 77 – kiselo sredstvo). Pokazalo se da alkalno sredstvo znatno bolje uklanja blokirajuće tvari s površine membrane. Osim toga ispitan je utjecaj radnog tlaka prilikom UF sekundarnog efluenta na ireverzibilnost blokiranja te utjecaj temperature alkalnog kemijskog sredstva na učinkovitost čišćenja. U konačnici je predloženo idejno rješenje za oporabu sekundarnog efluenta POŽN membranskim postupcima, a ono uključuje predobradu koagulacijom pri utvrđenim optimalnim uvjetima, pješčanu filtraciju za uklanjanje zaostalih flokula, tri stupnja UF s MW membranom te završnu obradu UF permeata s XLE membranom. RO permeat ima potencijal za primjenu u proizvodnji pare, a RO retentat za održavanje higijene postrojenja i transportnih vozila. Primjenom predloženog rješenja moglo bi se oporabiti 47,3 % sekundarnog efluenta, 11,1 % kao kotlovska voda i 36,2 % za pranje podova.Rendering plants fulfill a key role in the sustainability of the meat industry by treating the resulting animal by-products – hazardous waste; thus, reducing the negative impact of the meat industry on the environmental and human health. However, the treatment of this type of hazardous waste results in a large consumption of water and the production of highly loaded wastewater. In order to solve these problems, this work investigates the application of pressure-driven membrane processes of ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) for the treatment and recovery of rendering plant secondary effluent after biological treatment. The rendering plant wastewater is highly loaded; thus, rendering plants must have a wastewater treatment system. The rendering plant wastewater has a high BOD/COD ratio, which makes it suitable for biological treatment. Therefore, this paper did not examine the direct treatment of rendering plant wastewater with membrane processes, but the treatment of its secondary effluent after biological treatment. So, the efficiency of commercial flat sheet (MW, GM, CQ, GK, PT, PU, and PW) and hollow fiber UF membranes (ZW-1) and NF (NF270, NF, and NF90) and RO (XLE) flat sheet membranes were examined. The process efficiency was evaluated based on the following parameters: electrical conductivity (κ), turbidity, carbon content (total carbon – TC, inorganic carbon – IC and dissolved organic carbon – DOC), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), anions (Cl-, F-, NO2-, NO3-, PO43-, SO42-, and Br-) and cations (Na+, Ca2+, Mg2+, K+, NH4+, and Li+), and pH. UF membranes showed a similar separation effect, which included the effective reduction of turbidity and COD and the retention of DOC, but slightly worse nitrogen removal, as well as poor salt retention. On the other hand, NF and RO membranes retained nitrogen and dissolved salts significantly better, but their performance varied significantly depending on the membrane used. Pristine and fouled membranes were characterized with Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). Membrane fouling was modeled using modified Hermia models for the four fouling mechanisms (complete, partial, and internal pore blocking and cake formation). The hydrophilicity of the membrane surface was characterized by measuring the contact angle of water. In this work, the pretreatment of secondary effluent after biological treatment with sand filtration and a combined pretreatment of coagulation and sand filtration were evaluated as a strategy for membrane fouling mitigation of UF and NF membranes and UF as pretreatment for fouling mitigation of NF and RO membranes. Sand filtration was not successful in reducing the fouling of UF and NF membranes. Coagulation was optimized for the most suitable coagulation agent (from those tested: FeCl3, Al2(SO4)3, Aquaklar A (10% Al2O3), and Aquaklar C (18% Al2O3) and optimal working conditions (pH value and concentration of the coagulation agent). The most suitable coagulation agent was FeCl3 at pH value of 5.87 at a concentration of 10 mg Fe3+ L^-1. The combination of coagulation at optimal conditions and subsequent sand filtration resulted in a successful fouling reduction (50 – 95% lower flux decline) for UF membranes and 76 – 95% for NF membranes. On the other hand, using MW UF flat sheet membrane as pretreatment for NF and RO reduced the flux decline by 50 – 72%, while with ZW-1 hollow fiber UF membrane the reduction was 2 – 67%. The cleaning of UF membranes fouled during the treatment of rendering plant secondary effluent with two chemical agents (PermaClean 99 - alkaline agent and PermaClean 77 - acidic agent) was investigated. The alkaline agent performed significantly better at removing foulants from the membrane surface. In addition, the effect of the applied pressure during the treatment of secondary effluent on the irreversibility of membrane fouling and the influence of the temperature of the alkaline chemical agent on the cleaning efficiency was examined. Lastly, a conceptual solution for the reuse of secondary effluent by POZN membrane processes was proposed. The solution included the pretreatment of the secondary effluent by coagulation under determined optimal conditions, sand filtration to remove residual floccules. After the pretreatment, three stages of UF with MW membrane followed, and at the end, the UF permeate is treated with XLE membrane. The RO (XLE) permeate would be used for steam production, while the RO retentate would be used for washing factory floors and vehicles. The implementation of the proposed solution could recover 47.3% of secondary effluent (11.1% as boiler water and 36.2% for washing purposes)

Use of measurement transducers in ship's automation systems

U ovome radu obrađena je osnovna podjela značajka mjernih pretvornika, koje su namjene i opće karakteristike te tehničke karakteristike. Objašnjene su sve tehničke karakteristike koje su potrebne za projektiranje kvalitetnih mjernih pretvornika. Nadalje, podijeljeni su i objašnjeni mjerni pretvornici električnih i neelektričnih veličina, kao što su pretvornici za mjerenje struje, otpora, frekvencije, tlaka i temperature. Također je objašnjeno više vrsta mjernih pretvornika kao što je mjerenje tlaka pomoću pomaka, mjerenje protoka suženjem dijela cijevi i mjerenje momenta vodenom kočnicom. Objašnjena je struktura mjernih pretvornika kao senzora, pretvarača, inteligentnih senzora, digitalnih mjernih pretvornika, te su nakraju objašnjeni analogno-digitalni, digitalni i optički mjerni pretvornici, uključujući i osnove kalibracije.This final paper deals with the basic division of characteristics of measurement transducers, their use and purpose, general and technical characteristics. All the technical features needed to design high-quality transducers have been explained. Furthermore, the paper describes measurement transducers of electrical and non-electrical quantities such as the transducers for current, resistance, frequency, pressure and temperature. Numerous types of transducers are also discussed such as motion-actuated pressure measurement, capillary flow meter and torque measurement with water hydraulic brake. The structure of measurement transducers is explained, including sensors, transducers, intelligent sensors and digital measurement transducers, and finally analogue-digital, digital and optical transducers, as well as the calibration of such devices is explained