Measure against Algae Bloom in Bangkhen WTP - Optimum chemical dosing rate for Aulacoseira spp. removal -

Transcription

1 Measure against Algae Bloom in Bangkhen WTP - Optimum chemical dosing rate for Aulacoseira spp. removal - Chaweepan S. (MWA) Jantima L. (MWA) Shinichi SASAKI (WaQuAC-NET)

2 Contents. Cooperation between MWA and WaQuAC-Net 2. Introduction 3. Objectives of the Experiment 4. Experimental Condition 5. Result of experiment 6. Conclusion 2

3 . Cooperation between MWA and WaQuAC-Net 22, Signed MOU for technical cooperation 23, WaQuAC-Net and expert from YWWB held biological survey in Chao Phraya River 24, Surveyed algal diversity in MWA s water sources at upper stream and reservoirs 25, Surveyed algae in Chao Phraya River and West-side reservoirs. 26, Focused to chemical treatment method in WTP by jar testing 3

4 2. Introduction May, 25 Serious filter clogging by Aulacoseira spp. caused Bangkhen WTP shut down for a few hours May, 26 Drought crisis led to low dilution effect in the river resulting in Aulacoseira spp. bloom and shorten filter run of 3 WTPs Mitigation to reduce algae before entering WTPs May 2, 25 Filter surface were covered with Aulacoseira. 4

5 MWA s Water Sources and WTPs Mae Klong Dam Algae problem occurred in Chao Phraya River and effected to 3 WTPs. Raw water canal (West Bank) Samlae Raw Water Pumping Station Raw water canal (East Bank) 5

6 Algae Monitoring in MWA s Water Sources Chlorophyll a at 7 km upstream of Samlae RW Intake (µg/l) 5-Apr 6-Apr 8-Apr 2-Apr 22-Apr 23-Apr 25-Apr 27-Apr 29-Apr 3-Apr 2-May 4-May 6-May 8-May 9-May -May 3-May 5-May 6-May 8-May 2-May 22-May 23-May 25-May 27-May 29-May 3-May -Jun 3-Jun 5-Jun 7-Jun 8-Jun -Jun 2-Jun 4-Jun 5-Jun 7-Jun 9-Jun 2-Jun 23-Jun 24-Jun 26-Jun 28-Jun 3-Jun Upstream 7 km Chlorophyll a at Samlae RW Intake (µg/l) 5-Apr 6-Apr 8-Apr 2-Apr 22-Apr 23-Apr 25-Apr 27-Apr 29-Apr 3-Apr 2-May 4-May 6-May 8-May 9-May -May 3-May 5-May 6-May 8-May 2-May 22-May 23-May 25-May 27-May 29-May 3-May -Jun 3-Jun 5-Jun 7-Jun 8-Jun -Jun 2-Jun 4-Jun 5-Jun 7-Jun 9-Jun 2-Jun 23-Jun 24-Jun 26-Jun 28-Jun 3-Jun 3, 25, 2, 5,, 5, Aulacoseira spp. Counting (Unit/ ml) Samlae Intake Upstream 26/4/9 26/4/22 26/4/26 26/4/27 26/4/29 26/5/ 26/5/3 26/5/5 26/5/9 26/5/ 26/5/3 26/5/5 26/5/7 26/5/9 26/5/22 26/5/24 26/5/26 26/5/28 26/5/3 26/6/ 26/6/3 26/6/5 26/6/7 26/6/9 26/6/ 26/6/3 26/6/5 26/6/7 26/6/9 26/6/2 26/6/23 26/6/25 26/6/27 26/6/29 Thonburi WTP Samlae Intake Bangkhen WTP Samsen WTP

7 Samlae Intake MWA s Measure Against Algae Bloom Stop to abstract RW into canal when the peak of algae bloom reached intake Added CuSO 4 into RW canal at Samlae Intake Bangkhen WTP Added chlorine into RW before clarifier (Pre-Cl 2 ) and before filter (Intermediate-Cl 2 ) Increased alum dosage Decreased production rate Stopped recycle supernatant water from sludge lagoon Backwashed filter more often and prolonged the period of air scouring and water washing 7

8 3. Objectives of the Experiment ) To find the optimum dosing rate of CuSO 4 and Chlorine for getting the effect of on Aulacoseira spp. How? Jar test and microscope investigation 2) To verify the effect of countermeasure to the removal efficiency of Bangkhen-WTP How? Check residual Aulacoseira spp. in RW, CW, FW! 8

9 Jar test condition st Experiment 4. Experimental Condition min 2 nd Experiment min 3 rd Experiment min 9

10 5. Result of experiment st Experiment Vary Alum Dose in 5 ppm Pre-Cl 2,, Aulacoseira sp. (cell/ (Cell / ml) ml) Turbidity Res.Chlorine (mg/l) 322, 8 Aulacoseira sp. (cell / ml),,, , ,6 3, ,9.7 2,2, Turbidity (NTU) Res Chlorine (mg/l) Raw Water Alum Dose (ppm) BK-WTP Jar test criteria about NTU % Aulacoseira Removal Res.Cl2 is about 3.7 mg/l >>>> Not economical and customer complain Keep turbidity lower than NTU >>>> Get more than 9% algae removal Higher alum dose can remove more algae.

11 2 nd Experiment Vary Pre-Cl 2 with Alum 25 mg/l Aulacoseira sp. (cell / ml),,,,, Aulacoseira sp. (Cell (cell/ / ml) ml) Turbidity Res.Chlorine 322, 9,7 8,8 3,4,9 2, Raw Water Pre-Cl2 (mg/l) Turbidity (NTU) Res.Chlorine (mg/l) % Aulacoseira Removal Dosage of Cl 2 at 3 mg/l is enough to kill algae.

12 3 rd Experiment Are there any synergistic effect? CuSO 4.3 mg/l as CuSO 4.5H 2 O Pre-Cl2-5 mg/l Alum 25 mg/l,, Aulacoseira sp. (Cell / ml),,, Aulacoseira sp. (cell/ (Cell / ml) ml) Turbidity Res.Chlorine 322, 5,6 9,3 4,, 9,8 3, Raw Water Pre-Cl2 (mg/l) Turbidity (NTU) Res.Chlorine (mg/l) % Aulacoseira Removal Dosage of Copper sulfate is.. 2

13 Removal Efficiency of Bangkhen-WTP Date : May 24 th, 26 time. O clock Aulacoseira sp. (Cell / ml) Process Line 2,, 8, 6, 4, 2, Aulacoseira sp (Cell/ ml) Turbidity (NTU) %removal RW 4, - CW,58. 9 FW.35 4,,58 RW CW FW 3

14 6. Conclusion Actual treatment method performed very well. Especially, most of Aulacoseria was removed in the clarifier tank by enhancing coagulation capacity. Chlorine dosing is very effective for Aulacoseira removing. The optimum dosing rate of pre-chlorine is around 3 mg/l. The synergistic effect by dosing both chlorine and copper sulfate in jar test is not clearly effective. More experiments are necessary for selecting more effective and economic method. To cope with Aulacoseira problem, chemical dosing rate should be decided by counting Aulacoseira in jar test. 4

15 Thank you for your attention MWA s Governor attained the seminar on experimental result and discussion. 5