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Are the flushable wipes really flushable? Performance evaluation of flushable wipes

2024-10-18

How to evaluate the flushability of wet wipes? INDA (North American Nonwovens Association) and EDANA (European Nonwovens Association) updated the evaluation method for flushable disposable nonwoven wipes in the Flushability Evaluation Guide (4th Edition) released in 2018.
The guide contains a total of 7 flushability evaluation tests to test the flushability and biodegradability of products. Only after passing these 7 tests can it be called a "flushable product", which are toilet and sewer clearance test, shaking box decomposition test, household pump test, sedimentation test, aerobic biodegradation/biodegradation test, anaerobic biodegradation/biodegradation test, and municipal sewage pump test.

1. Toilet and sewer clearance test
Used to detect whether the wet wipes can be flushed down the toilet and whether there is a possibility of clogging the toilet and sewer.
The test system consists of a toilet and a sewer pipe, simulating a family of four using the toilet normally for 2 consecutive days and at least 3 times a day, and flushing the toilet 35 times in the order of flushing only water, flushing only wet wipes, and flushing wet wipes and simulated feces.
The condition for passing this test is that the distance between the center of mass of the additive should not continue to decrease when flushing for 5 consecutive times without using other tools such as toilet plungers.

2. Shaking box decomposition test
It is used to test the decomposition performance of wet wipes products when they are physically shaken in tap water or wastewater. The specific operation is as follows:
First, place the non-woven wet wipes sample in a shaking box filled with 2 L of tap water. After shaking at a certain frequency and amplitude for 60 minutes, transfer the sample to a porous sieve with an aperture of 12.5 mm, collect the sample left on the porous sieve and weigh it, and calculate the percentage of the dry weight ratio of the sample on the sieve to the original sample.
The condition for passing this test is that in the sample test, at least 5 samples have a decomposition rate greater than 70%. China's new flushability test for disposable sanitary nonwoven materials stipulates that the dry cloth shakes in a shaking box for 10 minutes, and the decomposition rate level exceeds 90%; the wet wipes shake in a shaking box for 60 minutes, and the decomposition rate level exceeds 70%.

3. Household pump test
It is used to test whether wet wipes will have an impact on household sewage pumps and sewage systems.
The test consists of a toilet, a sewer pipe and a sewage pump. By simulating the frequency of toilet use by a family of four, toilet paper and wet wipes samples are added for flushing according to the prescribed procedure (see Table 1). The test lasts for 6 days, with 2 test sequences per day, and each sequence is flushed 12 times.
The condition for passing the test is that the average amount of wet wipes samples remaining from the 2nd to the 6th day cannot exceed the amount of samples added per day.

4. Sedimentation test
It is used to test whether wet wipes products can settle in the sedimentation chamber of a septic tank, sewage pool or sewage treatment plant.
The specific operation method is to place the wet wipe sample in a transparent plastic tube with a diameter of 20 cm and 1 L of tap water, cut a 10 cm×10 cm wet wipe sample and place it in the tube to let it settle freely, and evaluate its sedimentation performance by calculating the sedimentation rate. The pass condition of this test is that the average value of the sinking speed of all sedimentation samples should be greater than 0.1 cm/s, and the percentage of sedimentation samples accounts for 95% of all samples.

5. Aerobic biodegradation/biodegradation test
This test is carried out in two steps, including aerobic biodegradation and aerobic biodegradation.
The first step is to place the sample wet wipes in activated sludge culture medium for 14 days under aerobic conditions, and test the sample mass that passes through a sieve with a pore size of 1.0 mm. The dry decomposition rate of the sample is required to be greater than 95%.
The second step is to place the sample in sludge culture medium for 28 days under aerobic conditions and calculate its carbon dioxide emission. The biodegradability of the sample is evaluated by calculating the percentage of carbon mass in carbon dioxide generated after sample decomposition to the carbon mass of the sample. The test is passed if the carbon dioxide production is greater than 60% after 28 days.

6. Anaerobic biodegradation/biodegradation test
This test is also carried out in two steps, including anaerobic biodegradation and anaerobic biodegradation.
The first step is to culture the sample in anaerobic culture mud for 28 days, then transfer it to the sieve, test the sample mass through the sieve with an aperture of 1.0 mm, and require the sample dry decomposition rate to be greater than 95%.
The second step is to cut the sample into pieces and culture it in digester sludge with low salt culture medium concentration for 56 days, and calculate its carbon dioxide and methane emissions. The biodegradability of the sample is evaluated by calculating the percentage of carbon mass in carbon dioxide generated after sample decomposition to the carbon mass of the sample.
The passing condition of this test is that the generation rate of carbon dioxide and methane is greater than 70% after 56 days.

7. Municipal sewage pump test
It is used to evaluate the impact of wet wipes on municipal sewage. The dispersibility of wet wipes is related to whether the municipal sewage system can work smoothly.
The specific operation is to make water flow through the submersible pump in a box equipped with a submersible pump, and place a wet wipe sample near the inlet of the submersible pump every 10 seconds to detect whether the power of the submersible pump changes relative to the baseline within a time interval of 1 second. This test needs to be carried out for a total of 5 rounds, and the condition for passing is that the increase percentage of the total average power relative to the baseline is less than 5%.

At present, the process technology of flushable wet wipes has made some progress, but it still faces some challenges, such as the stability of dissolution rate and material cost. With the increasing demand of consumers for sustainable products and the continuous development of technology, the process technology of flushable wet wipes will be further improved to provide consumers with a more environmentally friendly and convenient use experience.
In the process of preparing flushable wet wipes, it is necessary not only to ensure that the film formed by the flushable agent on the surface of the wet wipes has good degradation performance to ensure that the wet wipes can be quickly flushed, dispersed and dissolved in water, but also to pay attention to improving the safety and stability of the product to make it meet relevant standards and regulations. Through reasonable process design and material selection, the flushable wet wipes can be quickly degraded and dissolved in water, reducing the negative impact on the environment.