| Author | Lamsal, Prakash Raj |
| Call Number | AIT Thesis no.EV-97-25 |
| Subject(s) | Water--Purification--Coagulation
|
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of
Master of Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | The aim of this research is to identify the influence of presence of natural organic matter in coagulation and flocculation processes. The natural water composed of non homogenous organic compounds; namely, humic substances, amino acids, sugars, aliphatic and aromatic acids and other chemical synthetic organic matter. These are the main reasons to have a different organic removal efficiency in natural water than synthetic water containing homogenous organic matter, like humic acid or fulvic acid only. As a result, removal efficiency for natural organic matter reduced to 60% from 80% for synthetic water containing humic acid only at TOC 7 mg/L and pH 7. Whereas the presence of secondary compounds, like Ca++, Mg++ divalent cations, which are responsible for exerting hardness, have no significant effect on the removal of organic matter. It varied from 58% to 60% and 55% to 62% for Ca++ and Mg++, respectively. However, the adsorption of organic matter on clay caused increase in removal of organic matter from 60% to 75%. Similarly Molecular size characteristics of natural organic compound in raw water were investigated at optimum conditions. About 64% of higher molecular weight organic compounds reduced to 7%, whereas the remaining 36% of lower molecular weight organic compounds reduced to 26% only. Hence, organic compound with high molecular weight has higher removal affinity in coagulation process. In this study, alum were studied using jar tests to determine the optimum coagulant dosages, pH and residual aluminum for maximum removal of organic concentration. UV Absorbance at 260 nm was used as surrogate parameter for estimating indirect measure of the removal efficiency of the organic concentration. The optimum alum dose was increased from 140 mg/L to 1225 mg/L with increase in TOC of 4 mg/L to 25 mg/L, respectively. In all cases of TOC, the pH of 7 was found to be the optimum for efficient coagulation. Whereas, residual aluminum of less than 0.2 mg/L can be achieved if the pH in water varies from 7 to 9 at TOC of7 mg/L. The study of floe charaterization explained that with increasing of TOC from 4 mg/L to 25 mg/L in natural water, the settling velocity was increased by more than 350%. The CST test concluded that the floe formed with lower TOC concentration readily released the water. Thus, dewatering of floe will be easier than the floe formed with higher TOC concentration. |
| Year | 1997 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Visvanathan, C.; |
| Examination Committee(s) | Ishibashi, Yoshinobu ;Takizawa, Satoshi; |
| Scholarship Donor(s) | Her Majesty Queen Sirikit Environmental Scholarship
Program (RTG); |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1997 |