PLANNING INTEGRATED WATER MANAGEMENT AT COLLEGE OF MARSHALL ISLANDS: IMPLEMENTATION AND CHALLENGES

摘要

In 2006 the College of the Marshall Islands (CMI) in the Republic of the Marshall Islandsembarked on a 5-year redevelopment programme of the Uliga campus. An objective of theMasterplan was to achieve a water utility infrastructure on campus that was as self-sufficientfrom the municipal water supplies as possible. Rainwater collection, water treatment and sewagetreatment and alternative energy options for the campus were to be implemented. The utilitiesconcept was reported in a previous paper (Fullerton R. W., WEFTEC 2007). This paper reportson the implementation and success of the strategy.During the period 2007 - 2011 three new classroom blocks, an administration block and anenergy centre have been constructed. While the general programme of the Masterplan has beenfollowed there have been a number of changes and challenges to implement the strategy.Early in 2008 it became evident that a severe water shortage was likely in Majuro due to lowrainfall and that the municipal water supply would be restricted to intermittent distribution ononly 2 days per week. The College currently stored rain water was insufficient to maintain thefreshwater supply so the planned installation of the RO seawater desalination plant was broughtforward with a temporary installation prior to completion of the utilities centre building. Acontainerised 100m~3/day RO plant was installed with a temporary seawater supply taken from themunicipal saltwater toilet flushing reticulation. Difficulties arose from restricted seawatersupply and high TDS in the feedwater.The Masterplan concept for storage of both treated and roof water used flexible “bladder” tanksin building basements due to the difficulty of constructing leakproof below ground concrete tanksin a high saline shallow water table environment. In addition, the sealed bladder tanks alsoprovide a secure uncontaminated water supply should the buildings become flooded by adverseweather conditions. A graphic illustration of the vulnerability of low lying Pacific islands toseawater rise due to climatic conditions occurred in December 2008 when a combination of Kingtides and a tropical cyclone storm surge overtopped parts of the Majuro coastline and flooded intothe partially completed construction excavations. No significant damage was done but theconstruction programme was delayed.As part of the overall energy sustainability strategy photovoltaic panels were installed on thecompleted buildings. An initial installation of 57kW of PV panels provided some 350kWh ofgrid-connected power daily, which offset the 300kWh power requirements for 12 hours operationof the RO desalination water plant. Ultimately all buildings will be fitted with PV panels toprovide up to 250kW with excess power being exported to the local grid. A standby dieselgenerator has been installed to provide power during municipal grid outages and to maintainoperation of the grid connected PV inverters as they require external synchronising power.Operation of the generator with locally produced coconut oil as a substitution for imported dieselwill be part of an experimental energy sustainability programme conducted by the College.Air conditioning is the highest power demand on Campus. To reduce the energy demand aninnovative use of seawater cooled marine chillers was trialled to provide building airconditioning. Using the cooler seawater temperature allows the chiller to operate with greaterefficiency. There is a saving of up to 20% energy compared with multiple split unit airconditioners of similar cooling capacity. Providing a seawater well in the adjacent reef, withpumping and reticulation for up to 40L/s to service up to four chillers in different buildings was achallenge. Careful consideration of galvanic and stray current corrosion was required to protectthe pumps and chillers in a circulating seawater system, and even then some corrosion issuesoccurred.The installation of a reticulated seawater supply around the campus to provide air conditioningchiller cooling water provided an additional bonus. The RO desalination plant seawater feedcould be taken directly from the reject cooling water, obviating the requirement for a separatereef well and pumping system. The Masterplan intention was to provide separated plumbing forthe toilet flushing water within each building to “future proof” the possible use of reclaimedwastewater. With a piped supply of seawater available there is the option to revert to seawaterflushing in the event of extreme water shortages, allowing the College to fully utilise the outputof the RO desalination plant for potable water use. Because the RO plant 100m~3/d capacityexceeds the Campus demand and there is secure potable water bladder storage, the College hasbeen designated as a community emergency water source.In summary the CMI energy and sustainability implementation has met the broad objectives ofthe Masterplan. A comprehensive monitoring plant to record energy use is being implemented bythe College to quantify the actual performance and to provide guidance for future initiatives.