1. Introduction
Kam Tin River is located at Kam Tin where is the east area of Yuen Long and the northwestern part of the New Territories. The drainage area of Kam Tin River is around 44.3 square hvcc / kilometers and the horizontal length of the mainstream is around 13 kilometers. The river-head for this river is 400 meters north of the peak of Tai MO Shan and the high is 910 meters so it is the second highest river in Hong Kong. In Kam Tin river, KT 1, KT2 and KT3 are the water sampling stations, the KTl and KT2 where are located at upstream that nearby the Kam Sheung Road stations, as well as KT3 where is located in downstream that is additional station in Nam San Wai, Yuen Long.
At 80's, the main pollution source of Kam Tin River came from domestic wastewater, livestock waste and industrial wastewater like T fu factories. Also, farms, villages and the industries were without perfect sewage pipelines to discharge wastewater to the Kam Tin River. As-well —as,-there were large and small solid wastes and sour odor, such as oil and manure. They caused serious proble of water quality and health of the river. In order to avoid the worsening esc-iü sewage problem of Kam Tin River, the government began to implement different measures to LtlteV improve the water quality, such as the livestock waste control scheme in 1988 that the number of livestock farms were decreased in Kam Tin River. In addition, the government has been gradually implementing the planning and construction of rural sewerage systems and set up Deep Bay Water Control Zone to implement Water Pollution Control Ordinance to improve river water quality. Moreover, the overall compliance rate of this river water quality indicators of Kam Tin River in 2014, 2015 and 2016, respectively were 53%, 50%, and 66%. For the level of WQI in 2014 was fair but 2015 and 2016 were bad.
The purpose of this survey is through the practice of Environmental Protection Department to compare the water quality results. To e earc thé changes of some water quality parameter and the water quality index of this river in this survey.
Sites
For this enm , 3 mea-suving-points(KT1, KT2 and KT3) at the upstream and downstream of Kam Tin River were measured. The 2 upstream me uring po t (KTl and KT2) are located near EPD station in Kam Sheung Road. Village houses and nstruction site had been observed. As the mention above, since there was no sewage drainage c nnected to village houses, so the sewage produced from village houses were effluent directly t the river, to be the main pollution
source of river water. be c Cit
The procedure of water quality monitoring at 3 Itoring sta were same. At the day to process field work, the water sampling was conducted f". Using water bucket collected river
water at KTl and KT2 and using wate samp in ollected river water at KT3. After water sampling, several water quality parameters were measured in-situ. Multi-parameter probe was used to measure the temperature, conductivity, salinity and pH value. Optical dissolved oxygen
meter was used to measure the D.O (in mg/L and %). • brate&böfofe
to se. Turbidity meter was used to measure the turbidity. For multi-parameter
One bottle of water sample was collected for further laboratory measurements of suspended solids (SS), 5-days Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD) and Nitrogen, Ammonia (NH3-N). For the suspended solid measurement, the weight of suspended hid @filter paper in water sample was measured. For the 5-days Biochemical Oxygen Demand measurement, the change of biochemical oxygen demand was observed at first day and fifth day. For the Chemical Oxygen Demand measurement, the change of chemical oxygen demand of water sample was measured by spectrophotometer (HACH — DR2800). For the NH3-N measurement, the blank and the water sample were prepared. The NH3-N of w te sample was also measured by spectrophotometer (HACH — DR2800).
3. Results
27.5 0 C
In general, the-results-were-showed—by-mean-as- each water quality parameter able 1). The temperature of the water sample that took from Kam Tin River was partial warm because of all water sample were bove.
For conductivity, the average conductivity of KTl , KT2 and KT3 were similar that the three of them were arnilnd 211.75 to 220 PS/cm.
4n-terms--of salinity, KT 1, KT2 and KT3 were 0.09 to 0.1 ppt. In general, salinity of water that lower than 0.5 ppt are belongs to freshwater, it can show that the water taken from KT 1, KT2 and KT3 were freshwater.
4bout-the pH value, KT 1, KT2 and KT3 were similar that the three of them were around 6.80 to 7.07. This means that the three of them were comparatively neutral.
For the turbidity, the average turbidity of KT3 was 11.20 NTU, which was higher than KTl and KT2. The average turbidity of KTl and KT2 were 3.87 and 4.26. For the SS, the average SS ofKT3 was 4.00 mg/L, which was higher than KTl and KT2. The average SS of KTl and KT2 were 1.50 and 2.00.
-KxynCk-T2 Therefore, the concentration of suspended solids and turbidity of KT3 was greater.
For the DO, the average DO in mg/L and % ofKT3 was 5.94 mg/L 78.23%, which is lower than KTl and KT2. The average of DO in mg/L and % of KTl and KT2 were 7.80 mg/L,
100.3% d 7.61 mg/L, 99.45% This means that the content of organic matter of KT3 was eater than KTI and KT2. if 7 s c. necesqccv ce(cdicc
For the NH3-N, KT 1, KT2 and KT3 were similar that the three of them were around the COD, the average COD of KT3 was 31.67 mg/L, which was greater than KTl and KT2. The average COD of KTl and KT2 were 16 mg/L and 18 mg/L. Therefore, the content organic matter, including biodegradable and non-biodegradable, of KT3 was greater than KTl and KT2.
For the BOD5, the average BOD5 of KT3 was 20.95 mg/L, which was higher than KTI and
KT2. The average BOD5 of KTl and KT2 were 7.86 mg/L and 4 mg/L. Therefore, the content of biodegradable organic matter ofKT3 was greater than KTl and KT2. vestdfs des
4. Discussion
Concerning the compar• , It is compared the class result with the Water Quality Objectives (WQOs) of Kam Tin River (EPD monitoring stations KTl and KT2). According to the River Water Quality in Hong Kong in 2016, the key water quality objectives (Figure 1) are including pH range, maximum BOD5, maximum COD, suspended solids and minimum dissolve oxygen.
After compare with WQOs (Table 2), the were within the range of
QOs, the BOD5 were exceeded about 2.7 and 4.8 mg/L respectively, the maximum COD were exceeded about 1 and 3 mg/L respectively, the suspended solids were lower than WQOs
18 mg/L and the dissolve oxygen were 3.6 and 3.8 mg/L respectively. It shows that the class esult wa fine hen compared with WQOs. About the compliance, the WQOs of the Kam Tin •vers (Figure 2) tßalttiÄåe IttXalWTil lnNJkCi0ér overall compliance rate in 2016 was 66% and increasing in the past three decades. Also, the Water Quality Index gradings in Kam Tin River (Figure 3) shows that both stations in Kam Tin River (KTl and KT2) also received WQI grading of "Bad" in 2016.
Regarding the pollution sources leading to poor water quality of Kam Tin River, there are two main source pollution which are septic tank, livestock farm (Table 4). According to the River Water Quality in Hong Kong in 2016, 21 000 village houses are still using septic tank system, lead to the overloading septic tank discharge from the unsewered population of villager, contributed about 24% BOD5 loading in the river. Also, the remaining 34 livestock farms contributed about 3400 kg BOD5/day, 62% BOD5 loading i river. Factory discharges are controlled under the Water Pollution Control Ordinance.
As far as the Water Quality Index (WQI), after calculation (Table 3), sampling sites KTl and KT2 were grading "Good" and KT3 was grading "Fair" by using the WQI adopted by EPD (Figure 4, 5). It shows that the upstream water quality was better than downstream, because there was more upstream tributary conferencing pollutant to downstream (KT3). Also, downstream is less steep than upstream, its -rts po utant sedimentation
After compare the WQI and other water quality data (KTl & KT2) with previous monitoring data, (year 2014-2016). It shows that the WQI of KTl and KT2 (Figure 8) was stable in 2014 to 2016, but the WQI had a great improvement in class result, highly decrease to 5 and 6 respectively. Also, some of the other water quality of KTl (Figure 6) and KT2 (Figure 7) are improving obviously, including alini , pH, turbidity, suspended solids.
To solve the water pollution problem and Il/prove the water quality of Kam Tin River, it is suggested that to provide a public sewerage tank at Kam Tin and a financial aid to the swage producer to support villager, livestock farms and construction sites connect discharge to sewerage. For a long term, it can decrease the opportunities of water pollution caused by livestock waste, which was the main pollution source of Kam Tin River. After more and more livestock farms refund their licenses, the water quality of Kam Tin River