Odstranjevanje dušikovih spojin in kovin iz pitne vode z algami Chlorella sorokiniana

doktorska disertacija

Aleksandra Petrovič (Avtor), Marjana Simonič (Mentor), Zoran Novak (Komentor)

Povzetek

Glavni namen raziskav v okviru doktorske disertacije je bil preučiti odstranjevanje dušikovih spojin in težkih kovin iz pitne vode z algami vrste Chlorella sorokiniana. Pri odstranjevanju dušikovih spojin (nitrata, nitrita in amonija) iz vode z algami imobiliziranimi na Ca-alginat smo podrobneje preučili vpliv vrste zunanjega vira ogljika ter vpliv številnih drugih parametrov kot so vpliv števila celic, vpliv pH, vpliv svetlobe, vpliv količine biosorbenta, ipd. na učinkovitost odstranjevanja dušikovih spojin. Eksperimenti so pokazali, da lahko alge C. sorokiniana ob prisotnosti ustreznega vira ogljika učinkovito odstranijo dušikove spojine iz vode pri vseh testiranih koncentracijah posameznega hranila. Izmed štirih različnih preizkušenih virov ogljika smo najvišje učinkovitosti odstranjevanja nitrata dosegli ob uporabi grozdnega soka, medu oz. melase, medtem ko uporaba saharoze ni dala tako dobrih rezultatov. Eksperimenti brez dodatka zunanjega vira ogljika so bili najmanj uspešni. Ker grozdni sok in med v tovrstnih študijah do sedaj še nista bila uporabljena, so pridobljeni rezultati še toliko bolj pomembni za nadaljnje raziskave. Pri začetni koncentraciji nitrata 20 mg/L ob prisotnosti grozdnega soka, medu oz. melase, so se nitrati iz pitne vode odstranili po enem dnevu v več kot 93 %, pri začetni koncentraciji 100 mg/L pa po približno treh dneh in sicer v več kot 95 %. Razlog, da ti viri ogljika dajejo boljše rezultate kot saharoza, izvira iz njihove sestave, saj vsebujejo številna hranila, ki pozitivno vplivajo na rast alg in s tem na odstranjevanje dušikovih spojin. Popolno odstranitev amonija (z začetno koncentracijo 30 mg/L) ob prisotnosti nitrata (50 mg/L) smo dosegli v manj kot 3 dneh. Učinkovitost odstranjevanja hranil je bila odvisna predvsem od količine biosorbenta, koncentracije dodanega vira ogljika, koncentracije vira dušika in intenzitete svetlobe. % (B/H2O), s katerim je mogoče doseči zadovoljive učinkovitosti je znašalo 1/6,7. Študija vpliva prisotnosti alg C. sorokiniana na biološko odstranjevanje nitratov z aktivnim blatom iz pitne vode je pokazala, da imajo te alge izrazito negativen vpliv na proces denitrifikacije. Biološka denitrifikacija z aktivnim blatom pri začetni koncentraciji nitrata 100 mg/L je omogočala več kot 95 % učinkovitost odstranitve nitrata, medtem ko se je ob prisotnosti alg odstranilo le okoli 65 % - 70 % nitrata. Prisotnost amonija oz. uree v vodi je negativno vplivala na proces denitrifikacije. V nadaljevanju raziskav smo izvedli eksperimente biosorpcije kovinskih ionov, pri čemer smo študirali odstranjevanje Cu2+, Ni2+, Cr6+ in Cd2+ ionov iz pitne vode z imobiliziranimi algami C. sorokiniana. Ugotovili smo, da lahko z imobiliziranimi algami odstranimo do 97 % bakra, 51 % niklja in 74 % kadmija iz pitne vode. Odstranjevanje kroma se je izkazalo kot nesmiselno zaradi prevelike toksičnosti le-tega za alge in prenizkih učinkovitosti. Biosorpcija kovinskih ionov je bila močno odvisna od koncentracije posameznega kovinskega iona v vodi ter od pH vrednosti raztopine. Pri začetni koncentraciji izbranega kovinskega iona 25 mg/L smo z istim biosorbentom učinkovito izvedli tudi do 5 zaporednih biosorpcijskih ciklov. Najbolj toksičen efekt na alge C. sorokiniana so pokazali Cr6+ ioni, sledijo jim Ni2+ in Cu2+ ioni, najmanj toksični pa so bili Cd2+ ioni. Cd2+ ioni za razliko od ostalih ionov tudi niso imeli nobenega bistvenega vpliva na odstranjevanje nitratov. Ker biosorpcija tro-komponentnega sistema kovinskih ionov z imobiliziranimi algami C. sorokinana iz pitne vode do sedaj še ni bila raziskana, smo v nadaljevanju raziskav preučevali biosorpcijo dvo- in tro-komponentnih sistemov Cu2+, Ni2+ in Cd2+ ionov pri treh različnih koncentracijah kovinskih ionov (30, 50 in 100 mg/L). Biosorpcijske kapacitete posameznega kovinskega iona so upadale s številom kovinskih ionov prisotnih v vodi, najnižje so tako bile pri tro-komponentnem sistemu.

Ključne besede

alge Chlorella sorokiniana;dušikove spojine;imobilizacija;čiščenje pitne vode;biološko čiščenje pitnih voda;onesnažene pitne vode;vir ogljika;težke kovine;

Podatki

Jezik:	Slovenski jezik
Leto izida:	2015
Tipologija:	2.08 - Doktorska disertacija
Organizacija:	UM FKKT - Fakulteta za kemijo in kemijsko tehnologijo
Založnik:	[A. Petrovič]
UDK:	628.1.033:663.14.031.3(043.3)
COBISS:	19201046
Št. ogledov:	1832
Št. prenosov:	332
Ocena:	0 (0 glasov)
Metapodatki:

Ostali podatki

Sekundarni jezik:	Angleški jezik
Sekundarni naslov:	Study of nitrogen compounds and metal removal from drinking water with algae Chlorella sorokiniana
Sekundarni povzetek:	The aim of this research was to study the removal of nitrogen compounds and heavy metals from drinking water by algae Chlorella sorokiniana. Firstly, in the experiments on the removal of nitrogen compounds (nitrate, nitrite and ammonium) from drinking water by alginate immobilised C. sorokiniana, besides the impacts of the types of carbon source on the removal efficiencies of nutrients, the impacts of several other parameters were studied such as the impact of cell number, pH, light intensity, amount of bio-sorbent, etc. The experiments showed that algae C. sorokiniana in the presence of an appropriate carbon source efficiently removed nitrogen compounds from the water samples at all tested concentrations of nutrients. Amongst the four tested carbon sources, the highest nitrate removal efficiencies were achieved when using grape juice, acacia honey or molasses as carbon sources, while sucrose gave poorer results. The experiments without any external carbon source added were less successful. As grape juice and acacia honey until this date have never been used as carbon sources in such kinds of studies, the obtained results represent an important contribution for further research. At an initial nitrate concentration 20 mg/L in the presence of grape juice, honey or molasses, the nitrates were removed from drinking water after one day at rates of more than 93 %, while at 100 mg/L of initial nitrate concentration by more than 95 % over three days. The main reason that these carbon sources gave better results than sucrose arises from their compositions, as they contain various nutrients that could positively impact the algae growth and thus nitrogen removal. The complete removal of ammonium (at initial concentration of 30 mg/L) in the presence of 50 mg/L of nitrate was achieved in less than three days. The nutrient removal efficiency was highly correlated with the bio-sorbent amount, the concentration of added carbon source, the concentration and type of nutrient, and with the light intensity. Otherwise, sufficient nitrate removal efficiencies could be achieved with a beads/water ratio of 1:6.7 or smaller. The study on the impact of algae C. sorokiniana on the biological removal of nitrate from drinking water by activated sludge showed that this alga had a noticeably negative effect on the denitrification process. At an initial nitrate concentration of 100 mg/L, only 65 % %70 % of the initial nitrate was removed in the presence of algae, whilst conventional biological denitrification enables above 95 % removal. The presence of ammonium or urea slowed down the denitrification process. Furthermore, experiments regarding the bio-sorption of heavy metals were performed, wherein the potential was studied of alginate immobilised C. sorokiniana for removing Cu2+, Ni2+, Cr6+ and Cd2+ ions from drinking water. It was found that immobilised algae C. sorokiniana could efficiently remove up to 97 % Cu2+, 51 % Ni2+ and 74 % Cd2+. Removal of Cr6+ ions was unreasonable due to low efficiencies achieved and due to the strong toxic effects of these ions on algae. The bio-sorption of the metals was strongly affected by the initial metal ion concentration and initial pH. At an initial metal concentration of 25 mg/L alginate immobilised C. sorokiniana cells could be used within 5 or even more successive bio-sorption-desorption cycles and still sufficiently remove metal ions. The highest toxicity effect on the algal cells was noticed in the case of Cr6+ ions, whilst Ni2+ and Cu2+ ions showed quite lower toxicities to C. sorokiniana. The lowest toxicity was observed in the case of Cd2+ ions, which among all metals also shown the negligible impact on the nitrate removal. As bio-sorption of the multi-metal systems of heavy metals from drinking water by alginate immobilised C. sorokiniana had not been studied until now, the bi- and multi-metal systems of Cu2+, Ni2+, and Cd2+ were investigated at initial metal concentrations of 30, 50 and 100 mg/L.
Sekundarne ključne besede:	algae Chlorella sorokiniana;drinking water;carbon source;heavy metals;immobilisation;nitrogen compounds;Pitna voda;Disertacije;Dušikove spojine;Odstranjevanje;Kovine;
URN:	URN:SI:UM:
Vrsta dela (COBISS):	Doktorsko delo/naloga
Komentar na gradivo:	Univ. v Mariboru, Fak. za kemijo in kemijsko tehnologijo
Strani:	XV, 147 str.
ID:	9057286