Uklanjanje benzofenona i kofeina procesima prečišćavanja voda

Abstract

Benzofenoni i kofein su sveprisutni, kako u otpadnim, tako i u površinskim vodama, u koncentracijama od nekoliko ng/l do mg/l. Koriste se u proizvodnji kozmetičkih preparata, kao pojačivači mirisa i ukusa, fiksatori u parfemima, aditivi u plastici, sredstvima za čišćenje, u proizvodnji pesticida. Benzofenoni su UV filteri pa se često koriste u proizvodnji sunčanih naočara, kao i u proizvodnji sapuna i parfema, sprečavajući UV zrake da oštete miris ili boju proizvoda. BP-3 se najčešće koristi u kozmetičkoj industriji kao UV filter u kremama za sunčanje, losionima za telo, šamponima, bojama i sprejevima za kosu. Kofein se primenjuje u proizvodnji prehrambenih proizvoda, lekova i kozmetičkih preparata. Značajno se razlikuju po hidrofilnosti (benzofenon log Kow 3,18; benzofenon-3 log Kow 3,79; kofein log Kow -0,07). Usled nedostatka podataka o sadržaju odabranih predstavnika benzofenona (benzofenon (BP) i benzofenon-3(BP-3)) i kofeina (CF) u različitim tipovima vode (pre svega u lokalnim otpadnim vodama i rečnoj vodi) i njihovom ponašanju u tretmanima voda, izvršena su ispitivanja u efluentu tipičnog postrojenja za preradu otpadnih voda i rečnoj vodi Dunava. Utvrđeno je da su sve tri komponente prisutne u efluentu WWTP (BP od 0,112 µg/l do 0,146 µg/l; BP-3 od 0,00718 µg/l do 0,42 µg/l; CF od 0,2 µg/l do 12 µg/l) i u Dunavu (maksimalno detektovana koncentracija je za BP 0,95 µg/l, za BP-3 0,62 µg/l i za CF 0,7 µg/l). Pored ispitivanja sadržaja ovih jedinjenja ispitana je efikasnost nekonvencionalnih procesa u obradi efluenta WWTP (adsorpcija, koagulacije, PAC/CoA, PAC/UF) i konvencionalnih (adsorpcija, koagulacija) i nekonvencionalnih procesa (PAC/CoA, PAC/UF, CoA/UF) u obradi rečne vode. Pored toga ispitani su efekti prirodnih procesa prečišćavanja u rečnoj vodi. Nekonvencionalni procesi za prečišćavanje otpadnih voda su ispitani pri početnoj koncentraciji supstanci od 0,96 µg/l do 2 µg/l. Adsorpcija naaktivnom uglju u prahu se pokazala efikasnom (benzofenoni se uklanjaju >84% - >94% u zavisnosti od doze uglja, a kofein je moguće ukloniti i do 84%). Koagulacija dozama prirodnog koagulanta od 0,0375 ml/l i komercijalnog koagulanta FeCl3 od 4 mg Fe 3+ /l se pokazala neefikasnom za sve supstance (<20%). Hibridni PAC/CoA koji je ispitivan sa različitim dozama aktivnog uglja u prahu (5 i 20 mg/l), prirodnim koagulantom (0,0375 ml/l) ili komercijalnim koagulantom (4 mg Fe 3+ /l), pokazao se kao efikasan za uklanjanje BP, BP-3 i CF sa većom dozom uglja A od 20 mg/l (>88%). Hibridni membranski proces PAC/UF je pokazao visoku efikasnost za uklanjanje BP-3 (>68%) i CF (>99,95%) sa dozom uglja od 20 mg/l. Ispitivanjem biodegradacije BP, BP-3 i CF primenom laboratorijskog test filtra, postignuta je efikasnost uklanjanja pri koncentraciji od 20 µg/l od 90% do 99% i pokazano da su supstance biodegradabilne. Testovi toksičnosti pokazali su značajno smanjenje ukupne toksičnosti smeša tokom laboratorijskog testa, a rezidualna toksičnost u odnosu na D. magna može biti posledica nedetektovanih transformacionih produkata. Transportom supstanci kroz sediment Dunava uočeno je da sediment predstavlja efikasnu barijeru za oba testirana benzofenona, dok CF lako prolazi usled svoje mobilnosti (log Kow -0,07). Eksperimentima fotodegradacije potvrđeno je da degradacija benzofenona UV zračanjem zavisi od prisustva anjona (HCO3 -, Cl i SO4 2-) i DOC u vodenom matriksu. Iako primenjeno UV zračenje nije bilo realno za dezinfekciju u tretmanima voda, rezultati su pokazali značaj detaljnije procene kvaliteta vode u slučajevima kada se UV zračenje primenjuje.Za uklanjanje odabranih supstanci iz rečne vode ispitani su konvencionalni procesi (zasebno adsorpcija na aktivnom uglju u prahu i koagulacija komercijalnim koagulantom, BOPAC ® ) i hibridni ili nekonvencionalni procesi adsorpcije/koagulacije (PAC/CoA), adsorpcije/ultrafiltracije (PAC/UF) kao i koagulacije/ultrafiltracije (CoA/UF). Tokom ispitivanja PAC/CoA sa ugljem B (2 mg/l) i BOPAC ® (2 mg Al 3+ /l) u određenim procesnim kombinacijama, (tokom sukcesivnog dodavanja prvo uglja B, a zatim koagulanta) uočene su specifičnosti za BP, efikasnost uklanjanja BP je iznosila 92%. U slučaju doziranja prvo koagulanta, a zatim uglja B i tokom simultanog doziranja koagulanta i uglja B, efikasnosti su iznosile 23 i 20%, redom. To je verovatno posledica kompeticije iliblokiranja pora uglja POM iz rečne vode. BP-3 se efikasno uklanjao tokom svih procesnih kombinacija sa ugljem B (87-93%), dok je za CF efikasnost uklanjanja iznosila od 0-12%. Hibridni procesi su se pokazali efikasniji pri primeni uglja C. U slučaju BP efikasnost je iznosila 81-90% i za CF 17-27% ,dok je za BP-3 efikasnost iznosila od 71% do 96%. Hibridni membranski procesi PAC/UF i CoA/UF u obradi rečne vode efikasni su u uklanjanju supstanci sa visokim log Kow. Benzofenoni su u hibridnim membranskim procesima uklonjeni od 69%-96% iz rečne vode, dok su za kofein utvrđeni promenljivi rezultati i potreba za daljim istraživanjima.

Benzophenones and caffeine are ubiquitous in wastewaters and in surface waters, in concentrations that vary from ng/L to mg/L. Benzophenones are used as: smell and flavor enhancers, perfume fixers, plastic additives, cleaning agents, as well as in the pesticide manufacturing processes. Their UV-resistant properties, makes benzophenones a suitable packaging component – to prevent UV light from damaging the odor or the color of the product. Similarly, benzophenone-3 is most commonly used in the cosmetics industry; as a UV filter agent in sunscreens, body lotions, shampoos, paints and hair sprays. On the other hand, caffeine is prevalent in food-, pharmaceutical- and cosmetics-manufacturing. However, benzophenones and caffeine have significantly different log Kow values. Log Kow values for benzophenone and benzophenone-3 are 3.18 and 3.79,respectively, while for caffeine log Kow is -0.07. Due to the lack of data on the content of selected benzophenones, (benzophenone (BP) and benzophenone-3 (BP-3)) and caffeine (CF) in different types of water (primarily in local wastewater and river water) and their behavior in water treatments, tests were carried out: a) in the effluent of a typical wastewater treatment plant (WWTP); b) and in the river Danube. In case of the WWTP effluent, the presence of all three compounds was detected in the following ranges: 0.112 μg/L to 0.146 μg/L for BP, 0.00718 μg/L to 0.42 μg/L for BP-3, and 0.2 μg/L to 12 μg/L for CF. With respect to the Danube river, the highest detected concentration for BP was 0.95 μg/L, for BP-3 was 0.62 μg/L, while CF in Danube river sample was measured in only one sample, resulting in a concentration of 0.7 μg/L. In addition, this work has investigated the efficacy of several treatment processes: unconventional processes in the WWTP effluent treatment (adsorption, coagulation, PAC/CoA, PAC/UF); as well as the conventional (adsorption, coagulation) and unconventional processes (PAC/CoA, PAC/UF, CoA/UF) in the treatment of river waters. Furthermore, the effects of natural purification processes in river water had also been examined within the scope of this research.Unconventional wastewater treatment processes were investigated at initial concentrations of selected substances that ranged from 0.96 μg/L to 2 μg/L. Adsorption on powder activated carbon was effective for removal of benzophenones (> 84% -> 94%) and caffeine (84%), depending on the dose of PAC A. Coagulation with doses of natural coagulant of 0.0375 mL/L and commercial coagulant FeCl 3 of 4 mg Fe 3+ /L was ineffective for all substances (<20%). Hybrid PAC/CoA process, investigated with different doses of PAC A (5 and 20 mg/L), natural coagulant (0.0375 mL/L) or commercial coagulant (4 mg Fe 3+ /L), proved to be effective for the removal of BP, BP-3 and CF at a higher PAC A dose of 20 mg/L (> 88%). The hybrid membrane process PAC/UF proved to be highly effective in the removal of BP-3 (> 68%) and CF (> 99.95%) with 20 mg/L of PAC A. Biodegradation of BP, BP-3 and CF had been confirmed in Danube river water sample using a laboratory test filter filled with inert material. The removal efficacy was 90-99% at a concentration of 20 μg/L. Toxicity tests showed significant reduction in total toxicity of the mixture during the course of the laboratory test, whereas the residual toxicity in relation to D. magna may be due to undetected transformation products. Transportation of the substances through the Danube sediment, indicated that sediment acts as an effective barrier for both tested benzophenones, while this is not the case with CF. Its mobility (log Kow -0.07) allows CF to pass through the sediment. Photodegradation experiments have confirmed that BP degradation occurs due to the presence of anions (HCO 3-, Cl 2-) and DOC in the aqueous matrix. Although the applied UV radiation was not a realistic representation of disinfection in conventional water treatments, the results showed the importance of a more detailed assessment of the water quality in cases where UV radiation is applied. Herien investigated are also conventional processes (separately adsorption on PAC, and coagulation with commercial coagulant - BOPAC ® ) and hybrid or unconventional adsorption/coagulation processes (PAC/CoA), adsorption/ultrafiltration (PAC/UF) and coagulation/ultrafiltration (CoA/UF) for the removal of the selected substances from river water.The efficiency of BP removal via PAC/CoA with PAC B (2 mg/L) and BOPAC ® (2 mg Al 3+ /L) observed specificity of removal of BP in certain process combinations, such as successive addition of first PAC B and then coagulant. The efficacy of such BP removal was 92%. In case of the initial coagulant dosing, then PAC B, and in the case of simultaneous dosage of coagulant anPAC B, efficacy were: 23% and 20%, respectively. Such outcome is probably a result of the competition/blocking of natural organic matter in river water. BP-3 was efficiently removed during all process combinations with PAC B (87-93%), while the efficiency of CF ranged from 0-12%. In general, hybrid process proved to be more efficient in case of PAC C. For BP and CF, the efficacy of removal amounted to 81-90% and 17-27%, respectively, wheareas the efficiency of BP-3 removal was found to be in the range of 71-96%. For the treatment of river water, hybrid membrane processes PAC/UF and CoA/UF are effective in the removal of substances with high log Kow. Benzophenones were removed from hybrid membrane processes by 69%-96% from river water, while caffeine was found to have less consistent results and requires further research.