The complexity of the reliability index of water and wastewater facilities
(to be discussed)

Summary

Reliability has been the most important feature of water and wastewater facilities. However no clear consistent definition of this notion and the procedure of calculating its indicators have been formulated so far. At present it can be done only with use the mathematical tool of the reliability theory. Most of the published editions on that subject offer one of the failure-free performance parameters as a reliability index without considering the fact that water and wastewater facilities are maintainable. Hereof it follows the need of using the integrated reliability index that takes into account both failure-free performance and maintainability. For the calculation of this index Markov model with continuous-time discrete state is used.

Key words

repairability , water and wastewater systems , Markov model , failure-free performance , integrated reliability index , simple index

Ways to improve the municipal water supply and distribution system

Summary

Simulation of all possible switch-overs in the municipal water distribution network caused by fault section cutoffs is practically unfeasible because of the large number of simulation cases. For the implementation a method of the distribution network dividing into separate districts (zones) with water flow rate measured at the input and outlet is suggested in a similar way to the elimination of leaks. Within the limits of each district including up to 50 km pipelines the search of the isolated sections becomes feasible. At that determining the reliability of the water supply in each district as a part of the annual period when the customer receives water on a regular basis is possible. This is achieved with the use of Markov model for determining the period of the water distribution network being operational and in the state with simultaneously isolated sections. Then by hydraulic calculations the parameters of the network in non-operating conditions are determined; at that it is determined which parameters are related to the operation period with normal or lowered level of performance.

Key words

water supply network , hydraulic design , water supply reliability , state of failure , state of failure , Markov model