Characterisation of the bioremediation processes in soil and groundwater contaminated by oil and oil derivatives at the site of Ratno Ostrvo

Abstract

<p>Predmet izučavanja ove disertacije je pasivna bioremedijacija naftom i derivatima nafte&nbsp;zagađenih podzemnih voda na lokalitetu&nbsp; Ratno ostrvo i pospe&scaron;ivanje procesa&nbsp;<br />bioremedijacije zemlji&scaron;ta i podzemne vode zagađenih naftom i derivatima nafte na&nbsp;laboratorijskom postrojenju u ciljusanacije ugroženog lokaliteta.</p><p>Praćenjem podzemnih voda granične zone izvori&scaron;ta Ratno ostrvo i Rafinerije nafte&nbsp;utvrđeno je da je u podzemnoj vodi granične zone izvori&scaron;ta Ratno ostrvo i Rafinerije&nbsp;nafte Novi Sad prisutan proces pasivnebioremedijacije, odnosno, da na pojavu&nbsp;ugljovodoničnog zagađenja u vodi sredina odgovara povećanjem brojnosti, pre svega,&nbsp;ugljovodonik-osidujućih i lipolitskih bakterija i bakterijske enzimatske aktivnosti, i&nbsp;dolazi do transformacije mineralnih ulja u polarna jedinjenja. U vodi većine praćenih&nbsp;objekata uočene su eksponencijalne i linearne funkcionalne zavisnosti bakterijske&nbsp;brojnosti i fosfatazne aktivnosti od koncentracije ugljovodoničnog zagađenja za&nbsp;koncentracije ukupnih ugljovodonika &lt; 400 &micro;g/l (najče&scaron;će &lt; 200 &micro;g/l). Visok nivo&nbsp;podzemnih voda i prisustvo dela zagađenja u gornjim slojevima zemlji&scaron;ta ukazuje nam&nbsp;na mogućnost primene fitoremedijacije navedenog područja, jer je deo zagađenja&nbsp;dostupan korenskom sistemu.</p><p>Ispitivanjem tehničke bioremedijacije zemlji&scaron;ta i podzemne vode zagađenih naftom i&nbsp;<br />derivatima nafte&nbsp; na laboratorijskom postrojenju utvrđeno je da dolazi do opadanja&nbsp;<br />koncentracije ukupnih ugljovodonika u zemlji&scaron;tu sa 38,2 na 14,6 g/kg i mineralnih ulja&nbsp;sa 27,0 na 10,2 g/kg (62%), &scaron;to se može definisati jednačinom C=C₀e^-kt, gde je&nbsp;<br />konstanta brzine degradacije ugljovodonika k=0,0082 dan^-1. U vodi je prisutan veliki&nbsp;<br />broj karboksilnih kiselinanastalih oksidacijom alkana (C10-19), kao i aromata&nbsp;(benzoeva kiselina, kao i benzaldehid), &scaron;to ukazuje na proces biooksidacije&nbsp;ugljovodonika. Proces rastvaranja i emulgovanja nafte se pospe&scaron;uje uvođenjem&nbsp;recirkulacije vode: određena je jednačina zavisnosti koncentracije ugljovodonika u&nbsp;vodenoj fazi od koncentracije u&nbsp; čvrstoj fazi, zavisno od&nbsp; brzine proticanja:&nbsp;C_voda=(f^*v+K₀)C_zemlja, gde je koeficijent ispiranja f=1400 s/m, a difuzioni koeficijent&nbsp;K₀=6^*10^-4. Proces ispiranja nafte i derivata sa zemlje značajno utiče na aktivnost&nbsp;mikroorganizama i razgradnju zagađenja. Sa porastom koncentracije ugljovodonika&nbsp;generalno opadaju brojnosti svih ispitivanih grupa bakterija i fosfatazna aktivnost i&nbsp;određene su granične vrednosti tolerancije. Proces ispiranja se &nbsp;mora voditi tako da&nbsp;koncentracija mineralnih ulja u vodenoj fazi netreba da pređe 15-35 mg/l, a kad se&nbsp;postignu koncentracije ugljovodonika manje od 400 &micro;g/l treba prepustiti pasivnoj&nbsp;bioremedijaciji da ukloni zagađenje.</p>

<p>This dissertation investigates the passivebioremediation of groundwater from Ratno&nbsp;Ostrvo contaminated by oil and oil derivatives, and a bench-scale experiment to improve the soil and groundwater bioremediation processes, with the goal of sanatising the effected area.</p><p>During groundwater monitoring of the zone between the Ratno Ostrvo spring and the&nbsp;Novi Sad oil refinery, a passive bioremediation process was observed, whereby, &nbsp;in the hydrocarbons-contaminated water, increased counts of hydrocarbon-oxidising and lipolytic bacteria and increasing bacterial enzyme activity were found, along with the transformation of mineral oils to polar&nbsp; compounds. In water, the majority of the&nbsp;monitoring points displayed either exponential or linear functionalal dependence&nbsp; between bacterial count or phosphatase activity and hydrocarbon concentration, for&nbsp; total hydrocarbon concentrations &lt; 400 &micro;g/l (most often &lt; 200 &micro;g/l). The high groundwater level and the presence of contamination inthe upper soil layers makes possible the application of phytoremediation at the site, as part of the contamination is in the rhyzosphere.</p><p>The bench-scale investigation of bioremediation in soil and groundwater contaminated by oil and oil derivatives yielded decreasing concentrations of total hydrocarbons in the soil from 38.2 to 14.6 g/kg and mineral oils from 27.0 to 10.2 g/kg&nbsp; (62%), which can be described by C=C₀e^-kt, where the rate constant of&nbsp; hydrocarbon degradation is k=0.0082 day^-1.</p><p>In water, a large number of carboxylic acids were present, from the oxidation of&nbsp; alkanes (C10-19) and aromatics (benzoic acid, and also benzaldehyde), which indicates a hydrocarbon biooxidation process. The process of dissolving and emulgating the oil is enhanced by recirculating the water: the linear relation between the concentration of hydrocarbons in the liquid and solid phases was found to be dependent on the flow rate: C_water=(f^*v+K₀)C_soil, where the rinsing coefficient f=1400 s/m, and the diffusion coefficient K₀=6 x 10^-4. The process of rinsing the oil and oil derivatives from the soil significantly influences the microbial activity and the degradation of contaminants. With increasing hydrocarbon concentrations, there was&nbsp; generally decreasing bacterial counts and phosphatase activity, and an upper limit for&nbsp; hydrocarbon tolerance was determined. The rinsing process must becontrolled to&nbsp; ensure the mineral oil concentration in water does not exceed 15-35 mg/l, and once the concentration of hydrocarbons becomes less than 400&micro;g/l, passive bioremediation may be left to complete the degradation.</p>