Coagulation of humic waters for diffused pollution control and the influence of coagulant type on DOC fractions removed.
This study examined the suitability of organic coagulants for treatment of typically humic peat extraction runoff water by comparing their performance with that of ferric sulphate (FS). The influence of coagulant type on dissolved organic carbon (DOC) fractions removed was analysed in detail using LC-OCD-OND (size exclusion liquid chromatography coupled with organic carbon and organic nitrogen detection) fractionation techniques. In general, lower coagulant dosage was needed under acidic (pH 4.5) than neutral (pH 6.5) conditions. Chitosan (Chit) and poly (diallyldimethyl) ammonium chloride (pDMAC) required significantly lower dosage (40-55%) than FS for acceptable purification, while a tannin-based coagulant (Tan2) required substantially higher dosage (55-75%) independent of water pH. FS demonstrated the best removal of DOC (<81%) and phosphorus (<93%) followed by pDMAC, while Chit and Tan2 achieved the highest removal of suspended solids (SS) (<58%), with flocs formed by Tan2 presenting the best settling properties. Higher molecular weight (MW) DOC fractions were more efficiently removed by all coagulants, with FS being the most efficient (biopolymers 69% and humic substances 91%), followed by Tan2. FS also displayed satisfactory removal of lower MW fractions (building blocks ∼46% and low MW neutrals 62%). Overall, FS was the best performing coagulant. Nevertheless, the organic polymers demonstrated satisfactory overall performance, achieving purification rates mostly inside the requirements set by Finnish environmental authorities.
['Heiderscheidt|Elisangela|E|', 'Leiviskä|Tiina|T|', 'Kløve|Bjørn|B|']
D001704:Biopolymers D002244:Carbon D005591:Chemical Fractionation D048271:Chitosan D002850:Chromatography, Gel D004058:Diffusion D005290:Ferric Compounds D006812:Humic Substances D006863:Hydrogen-Ion Concentration D009584:Nitrogen D010100:Oxygen D010758:Phosphorus D011095:Polyethylenes D000644:Quaternary Ammonium Compounds D012987:Soil D014867:Water D014876:Water Pollution D018508:Water Purification
Coagulation DOC fractionation LC-OCD-OND Organic nitrogen Organic polymers