Due to operational deficiencies and poorer maintenance, the Sri Lankan systems only operate, on average, about half the day. The operations and maintenance costs and tariff levels are strikingly different. In Sri Lanka, the tariff and operations and maintenance costs are both low, and with poor billing, large government subsidies are required. Operational improvements such as a reduced leakage rate and increased billing efficiency could greatly reduce the subsidy requirement. The simple treatment systems tend to be smaller in size than the full treatment ones.
Big systems are cheaper to run than small ones, indicating economies of scale.
It should be noted that economies of scale are more pronounced with the smaller simple treatment systems. There is a clear difference in cost with different engineering configurations. In each country, as expected, the cost of full treatment is more than simple treatment. These trends can be explained based on the cost of inputs and the effects of scale. In the smaller simple treatment systems the cost of labour dominates, while in the larger full-treatment systems costs are split rather evenly between labour, power and chemicals.