Water Journal : Water Journal April 2015
WATER APRIL 2015 62 Case Study: UGL BUDGET NO BARRIER TO INNOVATION Many innovative water authorities and contractors are striving to get more out of existing assets to solve new challenges. A good example of this is the recently completed upgrade to South East Water’s Boneo Sewage Treatment Plant (STP). B ack in 2007, South East Water engaged UGL to design, construct, commission and maintain a major upgrade to the Boneo STP. The main challenge for this plant is the five-week summer holiday period, with an 80% increase in load over a period of a few days, leaving no time for any adaptation of the biomass. The selected process was a modified activated sludge plant designed for maximum ammonia-nitrogen removal and some denitrification. The major upgrade was completed by UGL in 2009 and passed performance trials the following winter and summer. THE CHALLENGE Due to a higher than anticipated growth in load from new connections and future planned connections, the plant was predicted to be overloaded for the five-week summer holiday period in 2015, necessitating an investigation into plant capacity. Duplication of the plant was not warranted, as the upgraded plant and equipment could cope with the load for 11 months of the year for some time yet, so the brief was to defer large capital expenditure, deal with this short-term load and install equipment with minimal upset of the “live” plant. THE SOLUTION The first step was to install extra air capacity with two new magnetic bearing blowers. These units were much more efficient, smaller and quieter compared to traditional blower technologies. UGL performed a whole-of-life cost analysis to determine the type of blower required, and while the selected technology had a higher capital cost, the pay-off was calculated to occur after the first full year of operation. The second step was to install additional aeration equipment. The existing diffuser system had functioned very well, but it was going to be difficult to add more diffuser grids without taking the ditch off-line and cutting out some concrete baffle walls. Even lift-out grids were not easy to fit into the available space. The solution was to install four submerged aerator/mixers in the biological reactor, two into each of the ditches to cater for the peak periods. These units were easily installed into the operating plant with valuable benefits: • No fixing to the floor, with a flexible hose connection to the new air header; The new high-efficiency blower.
Water Journal February 2015
Water and CSG