Graduation Study Tour Report

  1. Time:

January 15, 16, 17, of 2010.

  1. Locations:
  2. Hai Duong Sole Member Limited Company.
  3. Cam Hoa Water Enterprise.
  4. Cam Thuong 1 Water Supply Enterprise.
  5. Cam Thuong 2 Water Supply Enterprise.
  6. Hai Phong Sole Member Limited Company.
  7. Cat Ba town water supply system.
  8. An Duong clean water production Enterprise.
  9. Vat Cach water supply JSC.

  • Attendants:

39 students of 05N1 (absence: Nguyễn Thế Hoàng, Lê Thanh Hải, Mai Xuân Nguyên).

Lecturers from Urban Department:

+ Doctor Mai Liên Hương – Head of Urban Department.

+ Master Deo – Geodetic Surveying Lecturer.

+ Master. Nguyễn Văn Nam – Pumping Station and Intake Facility Lecturer.

+ Master. Trần Văn Dân – Biological Laboratory.

+ Master. Nguyễn Tiến Dũng – Water supply and Drainage for Buildings Lecturer.

  1. Itinerary:

Truong Chinh road – Dương Xá Gia Lâm – phố Nối Hưng Yên

  1. Progress:

VI.1. Hai Duong Sole Member Limited Company

Address: No 10 – Hồng Quang – Hai Duong city.

Mr. Doan – engineer of the company was being assiged as our guide to visit.

VI.2. Viet Hoa Water Supply Enterprise.

Address: Cam Hoa street.

It’s invested by Japan capital with total investment is 400 billion VND, finish and started to operate on 2001.

Using underground water Như Quỳnh – Phố Nối with 8 drilled well.

Technology line:

Pic 2

Pic 3

At that time, in control room, it showed that: Pumping Station 1 is resting, Pumping Station 2 is working with capacity of 303.5 m3/h

Here, giàn mưa is being used as aeration facility to eliminate Fe and Mn trong nước nguồn.

To eliminate Fe, pH need to be 7.5 ÷ 8.5.

To eliminate Mn, pH need to be 8.5 ÷ 9.5.

In this pH space, the reaction happens strongest.

pH of water is low one part due to it contains lots of CO2. Here includes CO2 cavitation/entrusion and free CO2. Free CO2 is being eliminated by air, entrusion CO2 is being eliminated by Ca(HCO3)2.

Chlorine is being used with 2 purposes:

+ Eliminate remaining Mn

+ ensure that remaining Chlorine in water at the end of the pipeline on network is 0.3 ÷ 0.5 mg/l.

Clean water pumping station use 4 Ebara pumps, in which, one pump has Q = 1.95 m3/minute, H = 55m; one pump has Q = 3.55 m3/minute, H = 55m.

The pumping station uses Inverter to control pumps, there are 2 Inverters VLT1 and VLT2. At that time, only VLT2 works with frequency of 42Hz in range of 0 ÷ 50 Hz.

According to officers here, Inverter control flow automatically, not by valve. Using Inverter, saving electricity more.

Flocculation is alum, sedimentation supporting chemical is PAC. Currently, a chemical quantitative machine – made by workers here – is being used. Accuracy to 0.03kg.

Officers told us that using PAC help to save 35 ÷ 40% alum.

Station uses vertical baffle reaction tanks, dimensions BxLxH = 2x20x4 (m). Reservoir has volume 2400 m3, height 4m, is being equiped alarm whistle when water is over flow.

2 vertical sedimentation tanks have dimensions BxLxH = 5x21x3.3 (m), Q = 10.2 m3/day, started operation on Feb 2002. It uses hydraulic sediment discharge system.

Pumping Station:

Reservoir

Vertical baffle reaction tank

VI.3. Cam Thuong 1 Water Supply Enterprise.

Address: Phan Đình Phùng street, Cẩm Thượng ward, Hải Dương city.

Enterprise establish since 1936, original capacity 1000 m3/day.

1963, upgraded capacity to 5000 ÷ 6000 m3/day.

1978, upgraded capacity to 15000 m3/day.

1999: upgraded capacity to 70000 m3/day.

2008: Enterprise renovate vertical sedimentation tank to suspended sediment layer tank and increase capacity to 80,000 m3/day.

Raw water is from Thái Bình river, using inshore raw water intak facilities, around 500m from WTP.

Previously, WTP used perforated baffle mixing tank, now changed to vertical mixing tank.

Using PAC increase sedimentation effection: increase sedimentation velocity, decrease 60% alum need to use, decrease 50% price, water quality after sedimentation is good.

Comparison in suspended sediment layer tank:

+ Without PAC: sediment layer is 2m, v = 0.9 mm/s.

+ Within PAC: sediment layer is 1.5m, sediment particle is bigger, v = 1.2 mm/s.

Current average capacity is around 40000 m3/day. Water price 3500đ/ m3.

According to officers here, suspended sediment layer tank has high sedimentation effection. Although according to TC 33-2006, suspended sediment layer tank is recommended to use when water flow is changed not more than 15%, temperature changed not more than 10C in 1h but technical officer said: water temperature if changing is just one thin layer on surface, it’s hard to change deep inside, the surface water doesn’t have enough time to getting hot, already run out, so it doesn’t affect much to treatment process.

Currently WTP has 4 round suspended sediment layer tank, D = 8m, L = 5.4m.

Current safely water layer is 3.5m, but in actual with suspended sediment layer tank, just 1.5 m is enough, so the capacity can be upgraded when neccessary.

Filter tank dimensions BxLxH = 5mx5mx4m and there are 9 tanks, water distribution gutter width 90cm, thickness of sand layer in the tank is 1 ÷ 1.2m.

Current filting velocity is 15m/h, while theoretical filting velocity is 5m/h. So each 3 days need to clean the tank one time. There are 9 sedimentation tanks, so each day WTP clean 3 tanks.

The vertical filter tank was being renovated to suspended sediment layer tank has rectangular shape. Two round baffles were putted into the center of tank making 3 tanks in 1: inner is air removal tank, middle is sediment pressurized tank, outer is suspended sediment layer tank.

Normally, required chemical to treat water is: 50g PAC + 300g alum/ 1000 m3 water.

+ Reservoir: There are 2 Reservoir: one cylinder shape, one cube shape, volume of each tank is 2000 m3.

+ Clean water pumping station has 2 horizontal Ebara pump are working with Q = 540m3/h, H = 60m, P = 132kW. One preventive horizontal Ebara pump with H = 12m, Q = ?.

Suspended sediment layer tank

Pumping Station

VI.4. Construction site of Cẩm Thượng 2 Water Supply Enterprise.

This is invested by Netherlands capital, and are being provided, consulted about technology line, construction technical by Netherlands. The construction work itself are being done by Vietnam.

Construction started 06/2010 and estimated to finish by 10/2011 with capacity of 50000 m3/day.

It uses raw water from Thái Bình river. Raw water will flow into fiberglass pipeline D 700, L 500 ÷ 1000m. Then will be led to pre-settlement lake. There are 2 pre-settlement lakes, total square is 14000 m2. Depth of lake as average water level is 2.5m. Pre-settlement lake has floating boat sludge collection system.

The WTP use drying beds has mechanical sludge mixing system to make sludge dry faster and easier.

Construction of drying beds

Construction of regulating tank:

Pre-settlement lake:

We left by 10h45, having lunch and take a rest at Phương Nguyên restaurant, no. 52 – Cẩm Thượng – Hai Duong city.

VI.5. Hải Phòng Sole Member Limited Company.

We departed to Hải Phòng by 12:43pm. We were at their office by 1:45pm. We were accommodated in the meeting room of company. Mr. Vũ Mạnh Hoà – Vice Director introduced to us some info about history, organization and activities of the company.

(I cut down the whole content here)

The company has 504 staffs, in which 230 has University degree, 30 are water engineers.

Water resources are mostly surface water, ever tried underground water, but the quality is not good.

Hai Phong city has 7 WTPs, in which 5 WTPs belong to the Company, one WTP is JS, one is being leased. Total current capacity is 183000 m3. Normal capacity is 172000 m3.

Total length of pipeline is 250 km. Pressure at the end of network is 1.0 ÷ 1.2 Bar, (1 Bar = 10m).

Until end of 2009, the company served 220,000 customers.

Water loss: 16%, while average water loss of the whole country is 30 ÷ 40%.

We left the Company, depart to Cát Bà by 2:55pm

VI.6. Cát Bà town.

9am of Jan 16: we were at construction site of raw water pipeline from Gôi spring pumping station to WTP.

The pipeline was being constructed to pump water directly from Gôi spring pumping station to Thuồng Luồng station without booster pumping station.

Previously, galvanized steel pipe D100 and D150 were being used. Now due to demand is increased, need to use pipe D180.

Pipeline HDPE D180x10.7, L = 6m, PE 100, PN 10 is being installed. The pipes are made by Tien Phong Plastic JSC – No 02 – An Đà –Hải Phòng city. Price: 250000/ 1m.

Note:

HDPE: High density polyethylene

Pipe D180x10.7 : D180 is pipe’s diameter 180mm, for plastic pipe, it’s external diameter, pipe thickness is 10.7mm.

PE 100: Polyethylene type 100. 100 – value according to tensile strength of material.

PN 10: Working pressure at 20 độ C. Unit: Bar.

Pipe connecting method: thermal welding.

Construction time: 20 day/ 1.5 km pipeline.

Total workers: 10 people.

Regular workers: 4 people.

Surface elevation: 4.6m

Pipe bottom elevation: 4m.

Pipe connecting by thermal welding

Existing pipe and ditch for new pipe:

09:29am: We were at Thuồng Luồng pumping station, Bến village, Trân Châu commune.

It pumps water from Gôi spring pumping station and water from Thuồng Luồng spring to WTP.

There are two horizontal Ebara pumps Q = 1200l/min, H = 85m.

09:29am: We were at Thuồng Luồng pumping station, Bến village, Trân Châu commune.

It pumps water from Gôi springs pumping station and water from Thuồng Luồng springs to WTP.

There are two horizontal Ebara pumps Q = 1200l/min, H = 85m.

 

09:53am: We were at Cái Giá WTP – in the area of Cái Giá lake. It is invested from tourism development capital. Started operation on 2007, capacity Q = 3000 m3/day. Total investment capital of WTP and network was about 35 billion VND.

 

Raw water is both ground and underground water.

Ground water is from Gôi springs, Thuồng Luồng springs.

Underground water from Yên Xô well, Áng Vả well and from Hải Sơn area which is about 3 ÷ 4km to WTP.

There are 4 drilled wells at Hải Sơn area, Q well = 10 ÷ 15 m3/h.

Production process:

Underground water => areation facility tower => conical reaction tank => filter tank => Reservoir.

Aeration facility tower

Vertical mixing tank

Filter

Technical pipes of filter tank

Pumping Station

+ Aeration facility tower enriches oxygen for water and eliminate Fe.

+ Filter tank has total area is 26m2. It is built by reinforced concrete, floor has slab with strainer. Filter tank operates 24/24h with filter velocity is 5 ÷ 6m/h.

Filter tank is being cleaned by 3 phases: wind, wind + water, water. Cleaning frequency: 48 ÷ 60h.

+ Reservoir has volume W = 1000 m3, useful height H = 3.8m.

+ Water from Reservoir is being pumped to the hill which is around 2km from there, elevation is 42m, elevation difference is 38m in comparion with general ground (same function as water tower)

 

Output water has remaining Chlorine 0.7 ÷ 0.8 mg/l.

It serves around 1500 customers:

Include residential, restaurant, boats, ships, and other demands…

Water price:

+ Residential: 5000/ m3.

+ Service: 8000/ m3.

 

According to officer here, the WTP is being built based on design of a company in Hanoi. However, the design wasn’t suitable since aeration facility tower is quite big and costly while Fe level at Cat Ba is quite small. Technology line doesn’t have settlement facility lead filter tank has to over working (luckily that turbidity is low). Designer didn’t mention about eliminate salinity and eliminate hardness in water. However, it’s a touch problem which not any water engineer can solve.

 

Problems about water resource at Cát Bà:

+ It’s rare.

+ Unstable quality.

+ Underground water has high salinity and hardness.

 

WTP has:

+ One SAER wind pump, H = 180 m.

+ 3 Pentrax water pumps, Q = 900 ÷ 2600 l/min, H = 89.3 ÷ 54 m, f = 50Hz, n = 2900 round/minute.

 

Afternoon of Jan 16: visit Cát Bà bay and Quân Y cave.

VI.7. An Dương Water Enterprise.

January 17:

12:52pm: be present at An Dương Water Enterprise – 249 Tôn Đức Thắng –Lam Sơn ward –Lê Chân district – Hải Phòng.

 

VI.7.1 History:

– 1959 capacity was 20.000 m3/day.
– 1965 upgraded capacity to 60.000 m3/day.
– Currently 100.000 m3/day.

An Dương Water Enterprise is the main Enterprise, provide 75% total clean water of the Company. Each year Enterprise produces more than 38 million m3 clean water to people in Districts: Hồng Bàng, Lê Chân, Ngô Quyền, Hải An and some suburbans of Hải Phòng with high quality and being complimented by customers.

Enterprise is being fully furnished the ground water treatment technology system. The water resource is from Rế river. A closed and automatic treatment process help to reduce labor, and safe for surrounding environment.

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