In contrary to the fixed charge tariff, all of the following tariff systems base the customers wastewater bills on the amount of water used (consumption based charges) or the amount and quality of wastewater produced (effluent charges). All volumetric charges require that the consumer has a metered connection and that this meter works reliably and is read on a periodic basis. As domestic wastewater does usually not vary significantly in pollution load, it is rather uncommon to bill domestic wastewater services dependent on effluent quality. For industrial wastewater, however, pollution load differs widely and is usually considered in their wastewater bill.