At 11.00 a.m., Chow delivered a spare feed diaphragm pump and filter clothes for the filter press system. He advised us always to clean the surface of filter clothes using a water jet after using it.
Between 9.00 a.m. and 4 p.m., I observed the unit operations and meanwhile, I followed up on the commissioning projects in the WWTP site, mainly the new DAF operation.
Today we would monitor the colour (quality) of the effluent from DAF. We monitored the pH value of the fluid in the flocculator. The purpose of pH correction system is to provide a desired pH range for the physical-chemical process inside the flocculator. However, the reading displayed by the pH meter was unsteady and fluctuated within a wide range, e.g. from pH 4.0 to pH 7.0, which made it difficult to adjust the NaOH dosing system accurately.
Then Istiak guided us through the procedure of doing pH probe recalibration of the flocculator while performing the demonstration. He suggested us to conduct the recalibration every month or when the pH reading fluctuates within a wide range. Firstly the probe was rinsed with clean water. Two pH buffer solutions were used, with pH values of 4.01 and 7.01 during recalibration. Eventually, the pH reading varied with a narrow range, and the effluent was relatively clear.
Later he showed us the steps of operating the touch panel of the DAF
unit so that we can control the DAF system by adjusting the settings
accordingly. He explained to us the main differences between new and old
DAF units are:
(a) Air saturation system, and
(b) Sediment discharge system. An auger is installed for new DAF to compact, dewater and transfer the sediment towards the sediment valve, which is opened periodically releasing the sediment. Currently, the setting is once every hour.
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