Analiza uticaja prirodnih i antropogenih faktora na efikasnost procesa pripreme vode za piće iz površinske vode

Abstract

Predmet izučavanja ove doktorske disertacije je ispitivanje uticaja prirodnih i antropogenih faktora na kvalitet vode rijeke Vrbas koja se koristi kao resurs vode za piće grada Banja Luka. Identifikovani potencijalni negativni prirodni faktori su nagle obilne padavine, poplavni talas i pojava algi, dok su faktori ljudskih aktivnosti ispuštanje otpadnih voda,pražnjenje uzvodne akumulacije i sakupljanje plutajućeg otpada. U uslovima značajnog uticaja faktora na kvalitet vode, izvršeno je određivanje efikasnosti sistema pripreme vode za piće na industrijskom i pilot postrojenju. U skladu sa tim, eksperimentalni dio istraživanja obuhvatio je analizu vode rijeke Vrbas kao resursa vode za piće i analizu vode kao gotovog proizvoda nakon sprovedenog tretmana. Analizom istorijskih podataka poslednjih šest decenija o meteorološkim uslovima u slivu rijeke Vrbas, ustanovljen je porast temperature vazduha u poslednje dvije decenije za oko 2 °C kao i ekstremne količine padavina (do 1686 l/m2). Primjećene su promjene u sezonskim obrascima padavina, tj. Pojava dugotrajnijih padavina u ljetnjem periodu, koje su se najviše odrazile na vrijednosti mutnoće vode. Stoga je u cilju ustanovljavanja zavisnosti između količine padavina i visokih vrijednosti mutnoće vode kao i predviđanja za budući period primjenjen kratkoročni model neuronskih mreža. Primjenom ovog modela, uz korišćenje rezultata 2-časovnih mjerenja mutnoće riječne vode, mogu se uspješno predvidjeti promjene vrijednosti datog parametra za period od narednih 40 h. Porast količine padavina iznad 6 l/m2 se može smatrati alarmom za rano upozorenje pogoršanja kvaliteta vode rijeke Vrbas. Iako je u poslednjoj deceniji zapažen niži stepen trofičnosti jezera „Bočac“ u odnosu na prethodne godine, period nakon pojave poplavnog talasa karakterističan je po najvećoj brojnosti silikatnih algi (26 taksona). U periodu pojave algi na jezeru „Bočac“, dominantna vrsta bila je Pyrrophyta (4 taksona i 194 individue), a na visoku produkciju biomase algi ukazao je i sadržaj hlorofila-a (1770 mg/m3) i rastvorenog kiseonika (16,2 mgO2/l). U istom periodu na vodozahvatu dominantna vrsta bila je Bacillariophyta (25 taksona i 11055 individua), pri mutnoći vode >300 NTU. U periodu uklanjanja sedimenta iz akumulacije „Jajce II“ nikl je imao najveću vrijednost (77,4 µg/l Ni). Sadržaj amonijum i nitritnog jona značajno je povećan u odnosu na prethodno uklanjanje sedimenta iz akumulacije, što može ukazivati na starenje akumulacije, odnosno povećanje njene zamuljenosti. Uklanjanje amonijum jona u procesu prerade vode konvencionalnim procesom, bilo je loše za ulazne vrijednosti >1,0 mgNH4+/l, što je prouzrokovalo njegovu pojavu u vodi za piće. Uklanjanje nitritnog jona bilo značajno (do 97%) za cijeli opseg detektovanih vrijednosti. Primjena ozona (pilot postrojenje) u bilo kojoj dozi nije uticala značajno na sadržaj amonijum jona u vodi, dok je uklanjanje nitritnog jona bilo potpuno. Biološko uklanjanje amonijum i nitritnog jona izvršeno je na brzini filtracije 0,8 m/h i pri hidrauličkom vremenu zadržavanja na biofilteru od 1,5 h, u temperaturnom opsegu od 7,1-9,8 °C. Kada je već formirana biomasa, povećanje brzine filtracije nije značajno uticalo na proces nitrifikacije. Rezultati ispitivanja mikrobiološkog kvaliteta toka rijeke Vrbas ukazuju na uticaj otpadnih voda kao izvora zagađivanja i potrebu za odgovornijim pristupom u sanitarnoj zaštiti samog vodozahvata kao i lokaliteta uzvodno od vodozahvata. Gasno-hromatografskom analizom stiropora identifikovan je veći broj organskih jedinjenja (47) u odnosu na plastiku (28). Najveću koncentraciju imao je heptahlor (1274,41 µg/kg) i naftalen (518 µg/kg), koji su detektovani na stiroporu. Naftalen je detektovan i u vodi (53,2 ng/l) što ukazuje da je došlo do njegove sorpcije iz vode na površinu stiropora. Velika varijabilnost mutnoće sirove vode u periodu pražnjenja akumulacije, uzrokovala je i neoptimalne uslove koagulacije, što je za posljedicu imalo povećane mutnoće nakon procesa glavnog i završnog bistrenja (>1 NTU). Upotrebom niskih doza polielektrolita (0,1 mg/l) uz primjenu aluminijum-sulfata, čini proces značajno efikasnijim, posebno za ulaznu mutnoću sirove vode od 10-25 NTU.

The subject of this doctoral dissertation is to examine the impact of natural and anthropogenic factors on the water quality of the Vrbas River, which is used as a drinking water resource in the city of Banja Luka. Identified potential negative natural factors are sudden heavy rainfall, flood waves and the appearance of algae, while human activity factors are the discharge of wastewater, the discharge of upstream reservoirs and the collection of floating debris. In the conditions of significant influence of factors on water quality, the efficiency of drinking water preparation system at industrial and pilot plant was determined. Accordingly, the experimental part of the research included the analysis of Vrbas river water as a drinking water resource and the analysis of water as a finished product after the treatment. The analysis of historical data of the last six decades on meteorological conditions in the Vrbas River Basin, established an increase in air temperature in the last two decades by about 2 °C as well as extreme rainfall (up to 1686 l/m2). Changes in seasonal precipitation patterns were observed, ie. Occurrence of longer-lasting precipitation in the summer, which mostly affected the values of water turbidity. Therefore, in order to establish the relationship between rainfall and high values of water turbidity as well as predictions for the future, a short-term model of neural networks was applied. By applying this model, using the results of 2-hour measurements of river water turbidity, changes in the values of a given parameter can be successfully predicted for the period of the next 40 h. An increase in rainfall above 6 l/m2 can be considered an alarm for early warning of deteriorating water quality of the Vrbas River. Although in the last decade a lower degree of trophicity of Lake "Bočac" was noticed in relation to previous years, the period after the appearance of the flood wave is characterized by the largest number of silicate algae (26 taxa). During the period of algae emergence on Lake Bočac, the dominant species was Pyrrophyta (4 taxa and 194 individuals), and the high production of algae biomass was indicated by the content of chlorophyll-a (1770 mg/m3) and dissolved oxygen (16,2 mgO2/l). In the same period, the dominant species in the water intake was Bacillariophyta (25 taxa and 11055 individuals), with water turbidity >300 NTU. During the period of sediment removal from the "Jajce II" accumulation, nickel had the highest value (77,4 µg/l Ni). The content of ammonium and nitrite ions is significantly increased in relation to the previous removal of sediment from the accumulation, which may indicate the aging of the accumulation, ie an increase in its turbidity. Removal of ammonium ions in the process of water treatment by conventional process was bad for the input values >1,0 mgNH4+/l, which caused its appearance in drinking water. Nitrite ion removal was significant (up to 97%) for the entire range of detected values. The application of ozone (pilot plant) at any dose did not significantly affect the ammonium ion content in the water, while the removal of nitrite ion was complete. Biological removal of ammonium and nitrite ions was performed at a filtration rate of 0,8 m/h and at a hydraulic retention time on the biofilter of 1,5 h, in the temperature range of 7,1-9,8 °C. When biomass was already formed, increasing the filtration rate did not significantly affect the nitrification process. The results of the examination of the microbiological quality of the Vrbas River flow indicate the impact of wastewater as a source of pollution and the need for a more responsible approach in the sanitary protection of the water intake itself as well as the site upstream of the water intake. Gas-chromatographic analysis of Styrofoam identified a larger number of organic compounds (47) compared to plastics (28). Heptachlor (1274,41 µg/kg) and naphthalene (518 µg/kg) had the highest concentration, which were detected on styrofoam. Naphthalene was also detected in water (53,2 ng/l), which indicates that it was sorbed from water onto the styrofoam surface. The large variability in the turbidity of raw water during the period of discharge of the reservoir also caused suboptimal coagulation conditions, which resulted in increased turbidity after the main and final clarification process (>1 NTU). The use of low doses of polyelectrolyte (0,1 mg/l) with the use of aluminum sulfate, makes the process significantly more efficient, especially for the input turbidity of raw water of 10-25 NTU.