Določanje kemijske potrebe po kisiku v odpadni vodi

Dular, Jože (author), Prosen, Helena (mentor)

Eden od parametrov onesnaženosti odpadnih vod je tudi kemijska potreba po kisiku (KPK), ki sem jo določal v svojem diplomskem delu. KPK sem določal s titracijsko in spektrofotometrično metodo. Analiziral sem tri različne vzorce in sicer vodovodno vodo, vodo iz potoka Glinščica ter gnojnico. S titracijsko metodo so bile vrednosti KPK 4,862 mg O2/L za vodovodno vodo, 9,739 mg O2/L za Glinščico in 13748,48 mg O2/L za gnojnico. Spektrofotometrično pa so bile vrednosti KPK 1909,381 mg O2/L za vodovodno vodo, 1898,550 mg O2/L za Glinščico ter 47069,449 mg O2/L za gnojnico. Rezultati pri titracijski metodi so bili v pričakovanem območju vrednosti, saj je Glinščica zelo čist potok in je tako nizek KPK realen, vrednosti za gnojnico pa so nekje okoli 15000 mg O2/L. Vrednost KPK mojega vzorca gnojnice je nekoliko nižja, ker je pred vzorčenjem deževalo in je tako gnojnica bila že predhodno razredčena. Primerjava rezultatov KPK med titracijsko metodo in spektrofotometrično metodo ni bila mogoča zaradi previsokih rezultatov pri spektrofotometrični metodi. Relativni standardni odmik pri nobeni metodi ni bil večji od 2 %, zato lahko sklenem, da sta metodi dobro ponovljivi. Iz rezultatov lahko sklenemo, da je nekoliko bolj ponovljiva spektrofotometrična metoda, saj relativni standardni odmik ni presegel 1 % pri nobenih določitvah. Iz rezultatov se vidi tudi, da je relativni standardni odmik manjši pri srednje velikih koncentracijah in se znatno poveča ob zelo visokih in ravno tako pri zelo nizkih koncentracijah.

• Language: Slovenian
• Keywords: odpadna voda, KPK, titracija, spektrofotometrija
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2021
• PID: 20.500.12556/RUL-128246
• COBISS.SI-ID: 71676675
• Publication date in RUL: 07.07.2021

Secondary language

• Language: English
• Title: Chemical oxygen demand analysis of wastewater

Abstract

One of the parameters for wastewater pollution is chemical oxygen demand (COD) and its determination is also the purpose of my thesis. I determined COD with titration and spectrophotometric methods. I analysed three different samples. First sample was tap water, second was water from brook Glinščica and third sample was liquid manure. With titration method COD values were 4.862 mg O2/L for tap water, 9.739 mg O2/L for brook Glinščica and 13748.48 mg O2/L for liquid manure. COD values determined with spectrophotometric method were 1909.381 mg O2/L for tap water, 1898.550 mg O2/L for brook Glinščica and 47069.449 mg O2/L for liquid manure. Titration results were more or less expected because brook Glinščica is known to be very clean so COD should be low. COD for liquid manure was a bit lower than normal. The reason for lower COD is because rain diluted the liquid manure before sampling. Comparison between titration and spectrophotometric methods could not be made because spectrophotometric results were wrong. Relative standard deviation was lower than 2 % for titration method and lower than 1 % for spectrophotometric method. Based on these results spectrophotometric method is more repeatable. Relative standard deviation gets higher at very low and very high concentrations.

• Keywords: wastewater, COD, titration, spectrophotometry