Total Suspended Solids (TSS)

The Total Suspended Solids test or TSS is performed at a Wastewater Treatment Plant. To put it simply, it is to give the operator a working knowledge of how much solid material is entering the Wastewater Treatment Plant. Some important information about the TSS Bench Sheet:



The plant operator writes down on the bench sheet the necessary information for that day, such as the date that the sample was taken and who collected the sample, who analysed the sample, the location of the sample, the time the sample was put in the oven, the oven temperature, the time out of the oven and the ending oven temperature, the time the sample was started and finished (for instance if test is started at 8 a.m. on Monday morning, then it will be finished at 8 a.m. on Tuesday morning). This would be known as a 24 hour composite type sample. It is necessary to have two composite samples, one for raw wastewater and one for final wastewater sample, so two determinations can be made at the end of the test period. The raw wastewater sample will indicate how much total solids that have came into the plant and the final wastewater sample will indicate how much total solids is being released back into the environment.
The operator removes four weighing dishes, each containing one filter pad, from the desiccator, in which two of these will be used for the raw water testing and two will be used for the final water testing. Note: The desiccator and its purpose will be discussed in other material.
If you will note on the tip of the aluminum pan each pan has an individual number, in this case it is filter 1, 2, 3, and 4. This will stop any confusion of which filter is for the raw and final wastewater samples.
After removal from the desiccator each filter is weighed and the weight is logged on the bench sheet in its appropriate section.
The operator gathers the necessary items needed to perform this phase of the TSS.
The operator places the filter holder on the vacuum flask.
This facility uses Whatman's Glass Microfibre Filters grade 934-AH, circle size 47 mm. As you can see the operator is holding the filter pad with the tweezers (these filters are to be handled by mechanical device only).
The operator places the glass filter on the filter holder. Keep in mind that a filter holder is actually two pieces - top and bottom. There is a magnetic strip to help secure the fit over the filter.
The operator secures the raw water sample from the refrigerator, where it has been stored since that morning's collection. The operator takes a stirring stick and stirs the sample before it is poured into the graduated cylinder.
After pouring into the graduated cylinder, the operator notes and logs on his bench sheet the amount of the sample that was poured into the graduated cylinder. The amount was 154 mL.
The operator is turning on the vacuum pump.
The vacuum pump is on and running. The operator has a stop watch in his left hand which is used to time the test. The sample has to be run through the filter within a 10 minute time period (no more than 10 minutes is allowed). If the operator cannot achieve a 10 minute time limit, the filter must be discarded, reweigh a new filter and log it and reduce the amount of sample (for example, 100 mL) In this case it only took 6 minutes and 45 seconds for the amount to pass through the filter. So this test did not have to be voided. Two samples are to be done from the raw water and the two samples are averaged to come up with the total mL per liter for average for that particular test day. Note: After performing this test quite often, most operators can tell the amount of the sample that will go through the filter in 10 minutes time.
After each part of the testing, the operator must rinse with three 10 mL portions of distilled water. That helps to rinse down any particles that may be clinging to the filter holder. Note: The vacuum pump is still on and after the rinsing the vacuum pump will remain on for an additional 3 minutes. This will help remove water from the filter pad before drying.
The operator is showing the two raw water samples. Filter one is a sample from a 154 mL samples and filter two is from a 104 mL sample.
The operator now retrieves the final water composite sample, which was collected on the same day. The appropriate information is logged on the bench sheet. If you will note the graduated cylinder is a 1,000 mL or one liter graduated cylinder. The two samples, the final and raw are clearly indicated on the samples.
Because of the height of the 1,000 mL graduated cylinder, the operator places it in the sink so that the sample is easy to pour for safety purposes. The operator will pour 1,000 mL into the graduated cylinder.
The number three filter pad is being placed on the filter holder to prepare for the next phase of testing for the final composite sample.
As before, the operator replaces top of the filter holder. Turns the vacuum pump on and begins simultaneously pouring the sample and beginning the 10 minute time limit with the use of the stop watch. The amount of time for number three filter to run was 3 minutes and 9 seconds.
Again, three consecutive 10 mL portions of distilled water are run through the top filter holder to wash down any particles that may have adhered to the glass from the sample.
The process is repeated again using the number four filter pad and another 1,000 mL sample. Filter four took 3 minutes and 10 seconds to pass through. Again, the pump is left on for an additional 3 minutes to help pull any water off the filter pad to aid in drying.
The operator now places all four filters into the drying oven. Note: The drying oven should be turned on before the test is ever started, because the heat up time between 103 and 105°C takes a few minutes, depending on the drying oven.
The door is then closed to the drying oven and the operator periodically checks the temperature of the drying oven. The operator's left hand is on the thermometer, which actually runs into the drying oven, to determine the inside temperature. The operator's right hand is pointing to a calibration deviation that indicates whatever the thermometer says, he must subtract 1°C from it. At this plant, all thermometers are calibrated at least twice each year to ensure accuracy. After the drying oven has achieved a minimum of 103°C and no more than 105°C, the degrees and time is then logged on the bench sheet. All filters will be maintained between 103 and 105°C for a minimum of one hour.
At this point the operator must also log the time and temperature in the daily operational log, which is seperate from the bench sheet.
While waiting for the hour to pass, the operator cleans the work bench where the TSS testing was performed. This is done for safety purposes.
After a minimum of one hour has passed the operator does a final check of the temperature to make sure that it is between 103 and 105°C.
The filters have been allowed to dry for a minimum of one hour, the drying oven is then turned off. The operator then logs the time that the filters are put in the desiccator. Each filter is then taken out and placed in a desiccator. At the bottom of the desiccator there is a blue granule rock - this is an active color indicating desiccant, which is necessary. Putting it simply, if there is any water left on the filters after the hour of drying time, the desiccant will draw that out and its color will change from a blue to a pinkish color - this desiccant must be replaced if the color changes from blue because its efficiency in drawing moisture has diminished. The operator replaces the glass lid on the desiccator. To achieve an adequate seal between the lid of the desiccator a desiccator sealant that looks similar to vaseling is placed around the lid - just a thin film of sealant is used. If there is any excess sealant, it should be removed immediately. This sealant helps prevent moisture from entering into the desiccator. Without the sealant it is possible for enough filters to be placed into a desiccator, that as they cool, it may create a vacuum so powerful that the operator may damage the desiccator lid while attempting to remove it.
After the samples have been placed in the desiccator for at least 30 minutes, the operator then removes all four filter samples and lines them up to double check to makes ure that both raw and final samples are in the right order for weighing purposes.
Each filter, beginning with number one, is then weighed for the total weight of the sample which has been accumulated on each filter pad.
As each filter pad is weighed, the weight is then logged on the bench sheet in its appropriate section and column.
Let's look at the bench sheet closely to see what information has been placed on it. Basically what you see in each section and each column is the number of the filter pad. On the second row is the amount of each sample. The third row is the total weight. The fourth row is the empty weight of the filter. On the bottom row is the amount of the filtration time.
The operator now calculates to find out the average mg/L of the raw and final samples.
On filter number one, which is one of the raw samples, 154 mL was passed through the filter. At the end of the drying process the total weight was 126.9 mg. The empty weight of the filter was 110.1 mg. AFter subtracting, you get the net weight of 16.8 mg. The next calculation made is 16.8 multiplied by 1,000 divided by the volume of the sample, which in this case, was 154. This leaves mg/L of 109.1. The same calculations are made on filter two, three and four. Note: The net weight on all testing less than 1,000 mL samples must be at least 10 mg or the testing is invalid. Any sample of 1,000 mL is valid, even if the filter yield is less than 10 mg.
Calculate the average mg/L, and this is done by simply taking the two raw samples, which is filter one and two, and adding them together, which gives you 216.8 and divide by 2, which leaves you an average of 108 mg/L of raw total solids.
Calculate the average mg/L of the final samples, which is filter three and four. It is the same, bring down the 6.9 mg/L and the 5.2 mg/L and then add them together, which is 12.1 and divide by 2, which leaves you 6 mg/L. At this point it is necessary to determine the kilograms per day (kgd) and this calculation is achieved by taking the 6 mg/L and the flow of the plant that day in million gallons per day (MGD) and multiply those two together and then multiply the conversion factor of 3.785, which will convert the milligrams to kilograms. The total was 61 kgd. This also must be logged on the bench sheet.
This is the final view of the completed bench sheet.
It is also recommended to double check your calculations at this time for accuracy purposes to make sure that the bench sheet is filled out appropriately.
Now the information is taken from the bench sheet and what is necessary is placed on the state sheet that is submitted to the appropriate agency in the monthly reports.


View the TSS Benchsheet and the MLSS Benchsheet.