Monitoring data for potable water in the R.M. of Macdonald regional water system indicates elevated levels of chlorine disinfection by-products (DBPs), trihalomethanes (THMs). Dissolved Organic Carbon (DOC) and chlorine dose are the key precursors for the formation of THMs. Currently, the DOC is not removed efficiently at the Sanford water treatment plant, which supplies the R.M.’s potable water distribution system. The raw water DOC concentration incoming to the plant varied from 8.9mg/L to 31.8mg/L during this study. Sanford treated water effluent contained an average DOC of 6.5mg/L and the THM levels ranged from 86.6ppb to 175.7ppb. One of the objectives of this study was to conduct jar tests to optimize Sanford’s water treatment process to improve removal of DOC. Optimization of the coagulation process successfully reduced the DOC level in the plant effluent by 51% during the summer and 34% in the winter. The DOC reduction resulted in a THM reduction of 73.5ppb in the summer and 59.9ppb during the winter. Results showed that removal of 1mg/L of DOC eliminates 26.8ppb of THMs in summer and 11.9ppb during the winter. Another goal of this project was to investigate the relationship between THMs and their precursors, which includes: water DOC, free chlorine residual, and the chlorine contact time. Water samples were strategically collected throughout the Sanford regional water distribution system; the samples were tested for DOC, UV254, SUVA, chlorine residual, and contact time. A linear relationship between THM formation and chlorine contact time (R2 of 0.92) was found. This indicates that the content of THMs can be decreased by reducing the amount of time the water stays in the distribution system.

Monitoring data for potable water in the R.M. of Macdonald regional water system indicates elevated levels of chlorine disinfection by-products (DBPs), trihalomethanes (THMs). Dissolved Organic Carbon (DOC) and chlorine dose are the key precursors for the formation of THMs. Currently, the DOC is not removed efficiently at the Sanford water treatment plant, which supplies the R.M.’s potable water distribution system. The raw water DOC concentration incoming to the plant varied from 8.9mg/L to 31.8mg/L during this study. Sanford treated water effluent contained an average DOC of 6.5mg/L and the THM levels ranged from 86.6ppb to 175.7ppb. One of the objectives of this study was to conduct jar tests to optimize Sanford’s water treatment process to improve removal of DOC. Optimization of the coagulation process successfully reduced the DOC level in the plant effluent by 51% during the summer and 34% in the winter. The DOC reduction resulted in a THM reduction of 73.5ppb in the summer and 59.9ppb during the winter. Results showed that removal of 1mg/L of DOC eliminates 26.8ppb of THMs in summer and 11.9ppb during the winter. Another goal of this project was to investigate the relationship between THMs and their precursors, which includes: water DOC, free chlorine residual, and the chlorine contact time. Water samples were strategically collected throughout the Sanford regional water distribution system; the samples were tested for DOC, UV254, SUVA, chlorine residual, and contact time. A linear relationship between THM formation and chlorine contact time (R2 of 0.92) was found. This indicates that the content of THMs can be decreased by reducing the amount of time the water stays in the distribution system.

Abstract Chemical treatment is considered best available technology for purification of peat extraction runoff in Finland, due to its capability to remove dissolved organic carbon (DOC), suspended solids and nutrients. However, lack of optimisation and adaptation of this method for purification of diffuse pollution sources, e.g., peat extraction runoff, has led to significant fluctuations in purification efficiency. This thesis evaluated the suitability of commercially available coagulants for the treatment of typically humic water. Inorganic (ferric sulphate, aluminium sulphate and a mixed product) and organic (polyDADMAC, polyamine, chitosan and tannin products) coagulants were studied. Investigations included assessment of required dosage and the influence of process parameters (pollutant concentration, mixing, water pH and temperature) on coagulant performance. In addition, the process conditions in existing treatment systems were examined in field experiments aimed at identifying possible factors affecting purification. Ferric sulphate (FS) was the most effective of the coagulants tested. It produced excellent flocs and achieved higher removal efficiency, particularly for DOC, than the other coagulants. However, the dosage required for FS was significantly higher than for e.g., polyDADMAC and chitosan. Moreover, samples treated with FS displayed high iron concentration and acidic pH. The organic polymers achieved satisfactory results, but further research is needed before they can become viable alternatives to metal salts. The quality of peat extraction runoff water was found to vary significantly. It was also observed that variations in DOC concentration, even for particulate rich samples, controlled coagulant dosage and, consequently, treatment efficiency. For inorganic coagulants, mixing provided during flocculation had a more significant influence on purification than mixing provided during coagulation. This is relevant hence in now existing treatment facilities no mixing is employed during flocculation. Based on the research conducted, suggestions were formulated for process optimisation aimed at reducing variations in purification efficiency, thus increasing the reliability of the method and reducing related environmental impacts. / Tiivistelmä Turvetuotannon valumavesien käsittelyssä yksi parhaista käyttökelpoisistatekniikoista on kemiallinen käsittely, koska se pystyy poistamaan valumavedestä liukoista orgaanista hiiltä (DOC), kiintoainetta ja ravinteita. Tästä huolimatta kemiallisen käsittelyn optimointia ei ole tehty hajakuormitukselle, kuten turvetuotannon valumavesille, minkä seurauksena valumavesien puhdistustuloksissa on suurta vaihtelua. Tässä väitöstyössä tutkittiin markkinoilla saatavilla olevien kemikaalien sopivuutta turvetuotannon humuspitoisille valumavesille. Tutkimuksessa testattiin epäorgaanisia (ferrisulfaatti, alumiinisulfaatti ja näiden sekoitus) ja orgaanisia (polyDADMAC, polyamiini, kitosaani ja tanniinipohjaisia polymeerejä) koagulanttikemikaaleja. Tutkimuksessa selvitettiin koagulanttien annostarpeet sekä erilaisten prosessiparametrien (vedenlaatu, sekoittaminen, pH ja lämpötila) vaikutus koagulanttien toimintaan. Laboratoriotutkimusten lisäksi väitöstyö sisälsi kenttämittauksia turvetuotannon valumavesien tyypillisten kemiallisen vesienkäsittelyn prosessiparametrien selvittämiseksi. Tutkituista koagulanteista rautasulfaatti oli tehokkain. Se tuotti hyvin laskeutuvaa flokkia ja poisti parhaiten valumavesien orgaanista ainesta. Rautasulfaatti vaati kuitenkin selkeästi suuremman annostuksen kuin esimerkiksi polyDADMAC ja kitosaani. Lisäksi puhdistettuun veteen jäi paljon rautaa ja vesi oli hapanta. Orgaanisilla kemikaaleilla saavutettiin myös kohtalainen/melko hyvä puhdistustulos, mutta lisää tutkimusta tarvitaan ennen kuin ne voivat olla vaihtoehtona epäorgaanisille kemikaaleille. Turvetuotannon valumaveden laatu vaihteli paljon. Valumaveden orgaanisen aineen määrän vaihtelulla oli suurin vaikutus kemikaalin annostukseen ja puhdistustulokseen. Sekoituksista kemiallisen käsittelyn flokkulaatiovaiheen sekoituksella oli suurempi vaikutus puhdistustulokseen kuin koagulaatiovaiheen sekoituksella. Tutkituilla turvetuotantoalueilla ei kuitenkaan ollut tällä hetkellä riittävää sekoitusta flokkulaatiovaiheessa. Tässä väitöstyössä esitetään parannuksia kemiallisen käsittelyn optimointiin paremman ja vakaamman puhdistustuloksen aikaansaamiseksi humuspitoisille vesille.