Innovative solutions for the reduction of inflow and infiltration in sewer networks

Limiting inflow and infiltration (I&I) in sewer networks has many economic, environmental and public health benefits. The primary driver for the implementation of I&I reduction programmes has generally been driven by discharge consent conditions from a regional authority and/or by public pressure to eliminate the negative effects associated with sewage overflows and poor quality effluent discharges, rather than economic arguments. Using data from a number of New Zealand’s local network operators it has been found that the cost of I&I is significant and there are strong economic benefits for implementing I&I reduction programmes in certain situations. It has also been found that alternative network systems (such as pressure sewer and vacuum systems) offer economic advantages over conventional rehabilitation and replacement solutions.

This paper proposes to:

• investigate and define the economics of I&I in order to assist network owners in their decision making processes; and
• evaluate alternative solutions in terms of lifetime costs when compared to conventional I&I reduction options.