Investigation Of Typical Taste/odor (T/O) Problem In Domestic Water-source And Study On Control Technology

Taste/odor (T/O) problem has been an important problem in drinking water industry for a long time, and more and more drinking water T/O events have occurred in mang countries. With the deterioration of source water quality, drinking water T/O events have also attracted a lot of public attention in China. In addition, the odor can be smelled when the concentration of T/O compounds is up to only 10ng/L. Therefore, there is a great urgent need to identify the T/O compounds and control the T/O problems in drinking water. In this study, the concentrations of the two main T/O compounds (2-methylisoborneol, MIB and geosmin) in some typical source water are studied by using headspace solid-phase microextraction (HS-SPME) and detected by GC/MS. At the same time, the application of activated carbon adsorption and some oxidants oxidation, including ozone, potassium permanganate, chlorine etc. for them were studied. The main results are summarized as follows:1. Survey of MIB and geosmin in diffirent water-sourcesThrough the survey and analysis of domestic typical water-sources, two typical earthy and musty-smelling compounds, MIB and geosmin, were found to exist in many sources, especially MIB. And it is very difficult to remove MIB and geosmin for the conventional craft.2. Potassium permanganate for the elimination of MIB and geosminPotassium permanganate is not ideal oxidant to the elimination of MIB and geosmin. the elimination rate is about 10% and 25%, respectively. The adsorption of manganese dioxide also plays an important role, besides the oxidation of potassium permanganate. Because of coagulation aid of potassium permanganate, which is in association with the flocculant PACl, the elimination rate of MIB and the geosmin may enhance 10%.3. Activated carbon for the elimination of MIB and geosminActivated carbon can remove MIB and geosmin effectively. But the source water quality and particle size have a significant influence on the adsorption of MIB and geosmin. When TOC or UV254 of source water was higher, higher PAC doses would be needed. Study on used granular activated carbon (GAC) from some water works indicated that the GAC still kept a considerable adsorption capacity for MIB and geosmin even though it had been put into service for a long time. But the time is the longer the effect is the poorer. It was also found that the kinetic processes under different PAC doses could be predicted with HSDM through only one set of kinetic experiment.4. Investigation and control technology research of T/O problem cassed by geosmin in YH reservoirPre-oxidation treatment cannot eliminate geosmin, and ozone, chlorine dioxide, and potassium permanganate, and other oxidants will lead to the release of a large number of geosmin. These indicate that pre-oxidation treatment is not suitable to the removal of geosmin. PAC was applied to the control of T/O problem caused by geosmin in YH water works. When the concentration of geosmin in raw water was about 100ng/L, by adding 10 mg/L PAC, it was possible to control geosmin below its threshold (4ng/L) in finished water, and in its initial concentration of 800ng/L, at least PAC dosage of 30mg/L, correspondingly. In conclusion, although PAC has had an immediate effect on emergency treatment, In order to remove geosmin in the algae-laden water effectively, algae should be removed firstly. Furthermore, we need to pay attention to the destruction of algae and the release of odor.