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The flocculator needs to be cleaned when flocs start to build up in the tank otherwise they will affect the turbidity measurements at the end of the tank. It should be obvious from looking at the last unused section of the flocculator whether or not the tank needs cleaning. Flocs will have filled the the entire section. A pump and hose for cleaning the tank are next to the flocculator. Waste from the tank must be drained into the grit chamber next to the sedimentation tank. Waste cannot go into the sink because it clogs the sink. When cleaning is finished, water can be emptied from the hose by detaching it from the pump and elevating the end. Walking the length of the hose while elevating it should empty the entire hose. A shovel can be used to remove sludge at the bottom of the tank when the tank is completely empty.
Running Tank
The pump for the tank can be plugged in on the far side of the plant above the rapid mix.
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In order to get the tube settlers to stay at a 60 degree angle, rest the bottom end along supporting tube on one wall of the flocculator and the top end along the other side of the flocculator. This achieves approximately 60 degree angle. To keep the tube settler in place tuck the sampling line between a baffle and the wall. This is an effective way of securing the tube settlers. After moving them, the tube settlers are filled with air, tend to float. This can be prevented by submerging the tube settlers to fill them with water before connecting the sampling line. If they are not submerged, the tube settlers will fill very slowly. The seal between the tube settler and the turbidimeter must be air tight otherwise the turbidimeters will not fill. Check to be sure the sampling line is all the way in the bulkhead fitting if the tube settlers are not filling (push past initial resistance). Replace the tubing from the tube settlers to the turbidimeters when they are clogged or very dirty.
Turbidimeters
Turbidmeters should be checked before running any test in the flocculator. The turbidimeters tend to become clogged and usually give highly inaccurate readings after running for over 6 hours. Due to the low flow rate through the turbidimeters flocs tend to collect in the turbidimeter vials and settle out. This means that they need to be checked before a test is run and sometimes data collected after this length of time should be assessed carefully.
Turbidimeter vials should be emptied and washed out with tap waterdistilled water. There is a bottle near the tube settler pump for this purpose and distilled water can be obtained from the lab in the treatment plant. Swish for about 10 seconds and empty (note: if acid is used the water needs to be dumped down the lab sink). If there is still buildup or the glass is dirty wrap two Kim wipes around a brush until it is covered and use that to scrub the inside of the vial.
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If the turbidimeter reads dessicant, the dessicant needs to be changed. When looking down on the turbidimeter from the top there are four silver screws, one on each corner. When these are removed the entire top of the turbidimeter including vial and display can be lifted. It is inside this compartment that the desiccants are located. The desiccants are important because they keep the compartment with the turbidimeter vials dry. A humid chamber can cause condensation on vials that will give false readings.
When this occurs bring the desiccant back to Hollister room 150 and leave it in the heating oven overnight at 100ºF. This will regenerate the desiccant and it will become active again.
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Turbidimeters need to be \[recalibrated\|How to Calibrate Turbidimeters\] every two months. The recalibration kit is located in the AguaClara LAb in Hollister Hall. |
Sampling line
A common problem that occurs is that the lines from the sampling point to the turbidimeters fill with sediment and the pump is unable to get water through them. If this happens, you should remove the clogged line, including all connections, and clean them. As this is a common problem, you may want to clean the lines before starting an experiment to increase your chances of a successful experiment. Back washing them may also help solve this problem. Some times clogs form the inlet valve for the raw water sampling line. Toggling the valve to increase and decrease pressure in the line should solve this problem.
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