Analysis of flocculation/flotation as wastewater pretreatment

Abstract

The purpose of this bachelor thesis is to optimize pretreatment of a wastewater from cosmetic industry. The current cleaning process in industry consists of two steps, namely i) AOP (Advanced Oxidation Process), and ii) flocculation/flotation (FF). However, as the HEM (n-Hexane Extractable Materials) decreases the efficiency of the AOP process by heavily blocking the light to penetrate in the wastewater to be cleaned, a first FF in acid environment is introduced in the process as pretreatment. The parameters that were varied to carry out the optimization were i) Fe2(SO4)3 content added in first FF and, ii) H2O2 content. To precise, JAR tests were carried out to make the FF and the sample was put in a 1.8 L reactor and subjected to UV light in the AOP treatment. For the better distribution of the H2O2 and Fe2(SO4)3 addition to the cleaning process the design of experiment was used. The HEM measured was carried out according to standard method “United States Environmental Protection Agency (EPA), Method 1664, Revision B: n-Hexane Extractable Material (HEM; Oil and Grease) and Silica Gel Treated n-Hexane Extractable Material (SGT-HEM; Non-polar Material) by Extraction and Gravimetry”. We found that the percentage of removal is very high, it goes from 96.3% till more that 99.9%. In average, with this new first FF, the percentage of removal is 98.61% which represents a very high enough removal rate of HEM to achieve the WW disposal limits in most cases. Only 3 out of 9 experiments exceeded the emission limit of 100 mg/L of HEM due to the type of surfactant, which we can conclude it has a strong influence in the removal of HEM.

Namen tega diplomskega dela je optimizacija predobdelave odpadne vode iz kozmetične industrije. Sedanji process čiščenja v industriji je sestavljen in dveh korakov: 1) napredni oksidacijski procesi (ang. Advanced Oxidation Process-AOP) in 2) flokulacije/flotacije (FF). Prisotnost težkohlapnih lipofilnih snovi (TLS) znižuje učinkovitost AOP z preprečevanjem penetracije svetlobe v odpadno vodo, ki jo čistimo, zato smo uvedli predobdelavo FF v proces v kislem okolju. Parametri, ki smo jih spreminjali tekom optimizacije so bile: 1) dodatek Fe2(SO4)3 v prvi FF in 2) dodatek H2O2. FF process smo izvedli v t.i. Jar testu in potem smo 1.8 L vzorca smo dali v reaktor, ki smo ga izpostavili UV svetlobi v AOP obdelave. Za boljo razporeditev dodatka H2O2 in Fe2(SO4)3 v process čiščenja smo uporabili načrtovanje eksperimentov. Meritev LS smo izvedli glede na standard United States Environmental Protection Agency (EPA), Method 1664, Revision B: n-Hexane Extractable Material (HEM; Oil and Grease) and Silica Gel Treated n-Hexane Extractable Material (SGT-HEM; Non-polar Material) by Extraction and Gravimetry”. Ugotovili smo, da je bila uspešno odstranjevanja zelo visok, od 96,3% pa vse do 99,9%. V povprečju z novo začetno FF kar predstavlja dovolj visoko odstranjevanja TLS za doseganje mejne vrednosti za izpust odpadne vode v večini primerov. Samo 3 od 9-ih poskusov presegajo mejno vrednost TLS 100 mg/L, zaradi tipa površinsko aktivnih snovi, za katere lahko zaključimo, da ima velik vpliv na odstranjevanj TLSa.