The article compares different methods for measuring how well organic waste is broken down in waste treatment plants. The researchers looked at 18 plants in Poland using various technologies. They found a strong connection between two methods, AT4 and GB21, showing how well the waste was stabilized. They also found that the amount of dissolved carbon in the waste water can be used to monitor the breakdown process. This method is quicker than the other tests, making it a useful tool for waste treatment plants.