Title Definiranje metodologije određivanja koeficijenta odumiranja pokazatelja fekalnog onečišćenja u uvjetima pronosa kroz krški vodonosnik Title (english) Defining the methodology for the determination of the die-off coefficient for fecal indicator bacteria in the conditions of transport through the karst aquifer Author Željko Šreng Mentor Goran Lončar (mentor)Committee member Goran Gjetvaj (predsjednik povjerenstva)Granter University of Zagreb Defense date and country 2019-02-13, Croatia Scientific / art field, TECHNICAL SCIENCES Universal decimal classificationUDC ) 624/625 - Civil and structural engineering. Civil engineering of land transport. Railway engineering. Highway engineering Abstract Ovim radom predstavljena je metodologija za određivanje koeficijenta odumiranja pokazatelja fekalnog onečišćenja (Escherichia Coli i enterokoki) uslijed pronosa podzemnom vodom kroz analiziranu kršku sredinu. Jedan od ciljeva istraživanja bio je razlučiti procese odumiranja i retardacije te odrediti dominantni proces uklanjanja pokazatelja fekalnog onečišćenja u promatranom krškom slivu. Metodologija pretpostavlja sukcesivnu primjenu statističkog, analitičkog i numeričkog modeliranja u svrhu definiranja kapaciteta samopročišćavanja analiziranog vodonosnika (efekti sorpcije i odumiranja iskazani pripadnim koeficijentima). Analizirani vodonosnik Bokanjac-Poličnik smješten je u zaleđu grada Zadra.
Metodologija se sastoji od tri osnovna koraka; preliminarne analize (prikupljanje podataka, statistička obrada podataka), analitičkog i numeričkog modela pronosa onečišćenja. Preliminarne analize kao početni korak metodologije poslužile su u konkretiziranju određenih pretpostavki vezanih uz detektiranje pokretača povećanih koncentracija Escherichie Coli i enterokoka na analiziranim zdencima kao i u određivanju mjesta potencijalnog izvora onečišćenja. Na temelju analize vremenskih serija utvrđeno je kako je kiša dominanti pokretač povećane koncentracije onečišćenja na zdencima. Provedeni Integral Pumping Test poslužio je u određivanju potencijalnog mjesta izvora onečišćenja. Informacije iz preliminarnih analiza koristile su se u izradi analitičkog modela, okosnice predložene metodologije. Model je podijeljen na dva dijela, vertikalnu i horizontalnu dionicu toka. Prvi dio (vertikalni tok) odnosi se na perkolaciju od septičke jame do saturirane zone i kao rezultat je dobivena koncentracija onečišćenja na kraju vertikalnog toka CVAD. Drugi dio analitičkog modela odnosi se na horizontalno strujanje i pronos unutar saturirane zone, a kao rezultat je dobivena koncentracija onečišćenja na početku toka CSAT (inverzni postupak). Proračunom su definirane vrijednosti ukupnog koeficijenta odumiranja ktot za obje faze toka. Višestruko veća vrijednost koeficijenta ukupnog odumiranja dobivena je za vertikalnu dionicu toka (srednja vrijednost iznosi ktot = 8.25), uslijed utjecaja sorpcije na uklanjanje onečišćenja. Unutar saturirane zone koeficijent ukupnog odumiranja ktot se kreće u granicama između 0.1 i 0.5. Definirani koeficijenti odumiranja pokazatelja fekalnog onečišćenja, zajedno s izračunatim koncentracijama onečišćenja CVAD/CSAT korišteni su kao ulazni podatak u numerički model pronosa onečišćenja. Numeričkim modelom dobio se uvid u napredovanje oblaka onečišćenja, ali i provjerila točnost primijenjene metodologije usporedbom modelskih i izmjerenih koncentracija onečišćenja.
Abstract (english) This thesis presents the methodology for determining die-off coefficient of faecal indicator bacteria (Escherichia coli and enterococci) in terms of seepage through the karst environment. The main problem in exploring karst environment, which this methodology strives to cope with, is lack of field measurements, poor data on karst rock formation, and fractures and channels within it, and groundwater level dynamics. The analysed karst catchment Bokanjac-Poličnik is situated in the hinterland of the city of Zadar and extends to 235.07 km2. In water supply wells within analysed catchment a frequent occurrence of faecal indicator bacteria was observed. The appearance of Escherichia coli and enterococci at the water supply wells of the karst aquifers Bokanjac-Poličnik is an indicator of the existence of faecal pollution that is very dangerous for the environment and people living in this area.
During the period from 1/1/2012 to 19/10/2016 the EC/ENT monitoring was carried out in the supply wells. Besides concentration, in the implementation of the methodology the data of groundwater levels at the wells, the pumping rates and precipitation were used. The proposed methodology consists of three basic steps. Preliminary analyses as the initial step were use in concretisation of the certain assumptions related to the detection of increased concentrations of EC/ENT as well as in determination of the potential source of contamination. Time series analysis, Integral Pumping Test and quantification of flow (KarstMod model) were elementary parts of the preliminary analysis. Information from preliminary analysis were used in the development of the analytical model, the main part of the proposed methodology. The analytical model was constructed with the aim of resolving processes of sorption and die-off and determining the dominant factor in the process of natural removal of faecal indicator bacteria in terms of seepage through the karst environment. Within the model, two parts of the pollutant transport are integrated. The first part refers to percolation from septic tank to the saturated zone, and the second part refers to the horizontal flow and transport within the saturated zone (inverse procedure). Initial concentration at the septic tank C0 and final concentration in the water supply wells CB4,JEZ were the input dana in the model. The calculation yields pollutant concentration at the contact of vertical and horizontal part of the flow (CVAD and CSAT). The aim of the calculation was to obtain a set of optimization parameters-coefficients of the model that achieve a minimum difference in the concentrations ΔC = CVAD - CSAT. Reduction of pollutant concentration in the vertical section was associated with the process of natural die-off (ki) and sorption (k), while in the horizontal phase, due to the more pronounced rate of seepage, the effect of sorption was eliminated. The calculation was carried out for each of the suspicious sources of contamination and assumed seepage directions, with variation of the parameter-coefficient values in the transport model (percolation velocity vSAT, total die-off coefficient ktot = ki + k, hydraulic conductivity K and retardation coefficient R). Estimated die-off coefficient for both seepage phases were later used as an input in the numerical flow and transport model (MODFLOW). The numerical model gained insight into the progress of the pollution cloud, but also checked the accuracy of the applied methodology by comparing the measured and model pollutant concentration. The strategy used for creating the numerical flow and transport model was Single Continuum Porous Equivalent model.
Keywords
koeficijent odumiranja
krški vodonosnik
matrica
pukotine
krški kanali
pokazatelji fekalnog onečišćenja
sukcesivno modeliranje
Keywords (english)
die-off coefficient
karst aquifer
fractures
karst channels
matrix
faecal indicator bacteria
successive modelling
Language croatian URN:NBN urn:nbn:hr:237:936346 Promotion 2019-05-04 Study programme Title: Postgraduate doctoral study of the Faculty of Civil Engineering Type of resource Text File origin Born digital Access conditions Closed access Terms of use Created on 2021-07-20 13:53:41
