Time and motion field study in Vinh Long City

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Figure 4.5: Vacuum trucks of VLPWCO for FS collection Source: Author

The houses not covered by either the sewerage system or a septic tank in suburban areas or away from the main roads with sewer lines use simple pit latrines. These dry systems are often temporary, unimproved and unhygienic. The wastewater from the households without a septic tank flows to the nearby ditches or empty lands behind the houses while the wastewater generated from commercial areas and markets is not treated and directly discharged into the canals and rivers. Furthermore, as observed in the field study conducted in the city for this research and the subsequent discussion with the desludging operators of VLPWCO, septic tanks are not regularly desludged, thus probably releasing very poorly treated effluents. These issues contribute to the pollution of rivers otherwise caused by the accumulation of garbage and non-collected solid waste, agricultural activities, small industrial productions and activities from trade villages. Indeed, the monitoring report done by DONRE shows that the rivers of the city of Vinh Long have values that are several times above the water quality standards for TSS, ammonium, phosphate, and coliform. Health reports also reveal disease episodes such as acute diarrhea, hand foot and mouth disease, Japanese encephalitis, dermatological and gastrointestinal diseases, and dengue fever, which are for some related to poor sanitation.

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urban areas and will remain in place for many more years (ADB, 2015), but most are not properly maintained).

During the field study, a team of two desludging operators from the VLPWCO was followed and observed during a full working day. The 2.5 m³ vacuum truck (3.5 tons) used was a Japanese Hino 300 series Turbo Intercooler purchased in 2009, equipped with a tank made in Vietnam and a 18 kW pump from the Italian company Moro.

Except for a portion of the road in the city center under construction for the installation of stormwater drainage pipes, the traffic conditions were excellent during the whole day and showed no sign of traffic congestion. Some narrow roads had to be used but globally Vinh Long has a good road network, particularly a convenient 4 lane-road often used by the followed vacuum truck and along which is located the FS discharge site. It is to be noted that to access this site before discharge, a u-turn on the 4 lane-road was needed. At the traffic got heavier by the end of the day, this action required time and got rather hazardous particularly under night driving conditions.

Average speed was satisfactory (39.5 km/h) with peak speeds varying between 50 to 75 km/h. Despite taking place in December, the day of the field study was hot (around 30 degrees Celsius) and humid; a usual climate for a Southeast Asian city. No rainfall event occurred during that day. Pictures of the field study are shown in pages x to xiv.

The study started at 09h17 and lasted for 8 hours, 22 minutes and 30 seconds.

Each motion of the work executed by the municipal operators was individually timed and recorded. The data gathered that day for each motion is listed in Table 4.2. Each motion is numbered from 1 to 10 with additional information provided in the notes after the table.

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Table 4.2: Time and motion data from a full day of desludging work in Vinh Long City, Vietnam

Motion

#

Description Symbol in model

Desludging sites

1^st site¹⁾ 2^nd site²⁾ 3^rd site²⁾ 4^th site³⁾ 1 Travel from depot to

1^st site

13 min.

15 sec.

- - -

2 Travel from sludge discharge site to next site to desludge

- 12 min. 22 min. 21 min.

3 Preparation time⁴⁾ TPiz 61 min. 29 min. 13 min. 7 min.

4 Pumping time 31 min. 17 min. 12 min. 12 min.

5 Ending time⁵⁾ 29 min. 25 min. 7 min. 6 min.

6 Travel from desludged site to sludge discharge site⁶⁾

21 min.

21 min.

30 sec. 26 min. 22 min.

7 Discharge time 3 min. 7 min. 4 min 3 min.

8 Idle time (for breaks)⁷⁾ TIz 47 min. 0 0 0

9 Time for vacuum truck cleaning

TCl - - - 13 min.

10 Travel from sludge discharge site to depot

- - - 17 min.

45 sec.

Required time for desludging cycles

Cz (No. 1-10)

205 min.

15 sec.

111 min.

30 sec.

84 min. 101 min.

45 sec.

Grand total C1-Clast 502 min. 30 sec. = 8 hr. 22 min. 30 sec.

Notes:

1) The first desludged facility was a septic tank of more than 2.5 m³ constructed under a house with 5 users.

2) The second and third desludged facilities were on sites where the houses had been dismantled. The septic tanks needed to be emptied before the installation of new tanks and construction of the new homes.

3) The fourth site was at a beer factory.

4) The preparation time comprises any task required prior to pumping, which includes the time needed to access the septic tank or facility to desludge and the time for assembling sucking pipes and hoses.

TEiz

Viz PSilz

Viz DSilz

LDSD Sllast

LHDSz

Slz

LDH Sl1

LDSHz

Slz

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5) The ending time comprises all activities to be completed after pumping, which includes the dismantling and storage of the sucking pipes/hoses in the vacuum truck, payment for desludging operations, and signing of relevant documents.

6) The collected fecal sludge and liquid waste were discharged at the municipal landfill used for solid waste.

7) The idle time includes lunch and breaks taken during the working day.

In addition the data collected during the field study, an interview with the two desludging operators provided further information on their daily work. It revealed that their working day usually starts at 09h00 to end when the last desludging site scheduled for the day is completed. The number of sites to desludged within a day can vary depending on the number of registered demands. The operators usually work from Monday to Saturday. However, during busy periods, for example before the Tết celebration (Vietnamese New Year) or when compulsory desludging at schools and hospitals takes place (about 30 to 40 septic tanks in hospitals must be desludged every year by the operators), work can also include Sundays and end at midnight. By contrast, operators are allowed to quit their work place in the afternoon if all the demands of the day have been addressed. On the day of the field study, work ended around 17h40, which was the time of the return to the depot after the operators cleaned the vacuum truck at the discharge site following the last FS discharge.

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5. Efficiency assessment