Study On The Feature Of Raw Water Quality In Heihe Section Of Heilongjiang River And Its Purification Process

The Heihe section of Heilongjiang River is located in the northern cold regionsat high latitudes, winding through Xiaoxing’anling Mountains. Because of thegeographical location and the surrounding ecological environment, the raw waterquality has its particular feature. Annually, during the period of the end of Octoberto the end of April (the icebound period), the river is frozened. As the ice-surfaceseparates the river itself from the outside, the raw water quality is stable. During theseveral days that from the end of April to the May, i. e. the initial stage of thethawing period, the ice-surface is broken, and the chroma and CODMnsurge, but thetemperature and the turbidity value are still in a low level. The thawing period (fromMay to mid-June) is the hardest period for water purification in the whole year. Thechroma and CODMnare a little lower than those in the initial stage of the thawingperiod, thus these indexes still have a negative impact on the main process. FromJuly to the end of August is the rainy season, in when the rainfall makes the turbidityvalue increased significantly. The chroma and CODMnare much lower than those inthe thawing period, the raw water in this period could get a better purification effectby enhancing coagulation.Based on the analysis of raw water quality data of Heihe section from2009to2012, in the winter of2012, a technical reconstruction works was supplied in acertain water treatment plant that the raw water was bumped from the Heihe sectionof Heilongjiang River, and the raw water characteristics and treatment effect afterthe reform were seriously survied. The original water treatment process was asfollow: water intaking--static mixer--folded plate flocculator--inclined tubesedimentation tank--rapid sand filter--chlorination--water supply, while the reformedprocess was as follow: water intaking--pre-chlorine oxidation--hole-paltemixer--small-oillet grid flocculator--narrow-space inclined plate sedimentation tank--rapid sand filter--chlorination--water supply. After the technological reform,chlorine dioxide oxidation could reduce the concentration of organics. Dosage ofchlorine is6kg/h (about4mg/L) in the thawing period. Silicic acid was also used ascoagulant aids, while, it was sulphuric activated in the new technology. The dosageof activated silicic acid varied in different periods,2mg/L in the icebound period,6mg/L~7mg/L in the thawing period, and5mg/L in the rainy season. With thetechnological reform, in the case that the raw water quality in2013in the thawingperiod is much worse than the recent years, the output water quantity is impoved by15%, and50%in the rainy season. The removal efficiency of turbidity increasedfrom70%(before the reform) to nearly90%. The removal efficiency of chromaincreased from50%~80%(before the reform) to80%~90%. The water quality isequal to that in the recent rainy seasons in2013, and in the case of the same loadingrate, after the reform, the drug consumption could save about10mg/L. Theengineering economic analysis showed that the operate cost is expected to about11.16million yuan in2013and the total projected revenue is about33.6millionyuan. Compared with the revenue of29.3million yuan in2012, the income couldincrease4.28million yuan per year.