Measurement of water turbidity

U radu su praćeni neki od parametara ključnih za određivanje kvalitete vode te postupci predobrade vode. Praćenje i kontroliranje kvalitete vode je od iznimne važnosti, posebno u današnje vrijeme kada su potrebe za pitkom vodom na vrhuncu, a svjedočimo svakodnevnim onečišćenjem vode uslijed ljudskog djelovanja. Uz pomoć parametara poput mutnoće, boje i ukupnog sadržaja suspendiranih tvari može se procijeniti kvaliteta vode. Uzrok mutnoće su suspendirane i koloidne tvari u vodi koji uzrokuju raspršenje zračenja prilikom prolaska kroz uzorak. Moderna metoda mjerenja mutnoće se naziva turbidimetrija i izražava se u jedinicama NTU. Smatra se da je voda s mutnoćom manjom od 45 NTU dobre kvalitete za piće. Ukupni sadržaj suspendiranih tvari nam govori o prisutnosti suspendiranih tvari u uzorku i izražava se u mg (suspendirane tvari) / L (uzorka). Najučinkovitije metode za mjerenje boje su spektrofotometrijske metode i pritom se mjeri prividna i prava boja . Uzrok prividne boje su otopljene tvari, suspendirane i koloidne čestice, dok su uzrok prave boje samo otopljene tvari, te je prilikom mjerenja prave boje potrebno profiltrirati uzorak kako bi se uklonile suspendirane i koloidne čestice. Procesi predobrade vode služe za pripremanje vode na zadovoljavajuću kvalitetu. Provodeni su procesi koagulacije s otopinom željezovog klorida (FeCl3), flokulacije, taloženja i filtracije. Učinkovitost procesa predobrade vode prirodne vode procijenjena je na temelju fizikalno kemijske analize vode koje uključuje mjerenje mutnoće, suspedniranih tvari i boje vode. Pravilnu dozu koagulanta moguće je odrediti jar testom i uz pravilno doziranje koagulanta uklonja se većinu suspendiranih tvari te smanjuje mutnoću vode.The purpose of this study was to describe and measure some of the key parametars for determinig the water quality such as turbidity, total suspenden solids and water color. Tubidity is reduction of transparency of a liquid caused by the presence of undissolved matter. The more total suspended solids in the water, the murkier it seems and the higher the turbidity. Turbidity is considered as a good measure of the quality of water. Turbidity is measured in NTU (Nephelometric Turbidity Units). The instrument used for measuring it is called nephelometer or turbidimeter, which measures the intensity of light scattered at 90 degrees as a beam of light passes through a water sample. Total suspended solids (TSS) are particles that are larger than 2 microns found in the water column. Anything smaller than 2 microns (average filter size) is considered a dissolved solid. Most suspended solids are made up of inorganic materials, though bacteria and algae can also contribute to the total solids concentration. TSS is measured in mg (suspended solids) / L. Spectrophotometry is the quantitative measurement of the absorbance or transmission properties of a material as a function of wavelength. With spectrophotometer we can examine and determine color of water. There are two important terms – apparent color of water and true color of water. Apparent colour of water is due to dissolved substances and undissolved suspended matter, determined in the original water sample without filtration or centrifugation and true color is due only to dissolved substances, determined after filtration of the water sample through a membrane filter of pore size 0,45 μm. Coagulation and flocculation occurs in successive steps, allowing particle collision and growth of floc. This is then followed by sedimentation and filtration. If coagulation is incomplete, flocculation step will be unsuccessful, and if flocculation is incomplete, sedimentation will be unsuccessful. Jar test was used to estimate the optimal dose of coagulant needed in removing the charged particles that occurred in raw water