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technical features refereed paper

COST ANALYSIS OF MEMBRANE TECHNOLOGY FOR WASTEWATER RECLAMATION D Young, C Hertle Summary

• M TP footprint requirements; and

Wastewater reclamation utilising membrane technology provid es a new opportunity to provide high standard Class A+ recycled water, suitable for reuse applications in community environments.

• A financial assessmen t (concept design level) of a MTP facility co mparin g membran e technologies for different treatment capacities. This will include capi tal, operations and maintenance, NPV cost analysis, and production cost estimates.

This paper reviews the manufacturers' specifi cations for four types o f membrane and conducts a finan cial analysis for hypothetical membrane treatment p lants of capacities berween 6 to 24 ML/d Whilst a pressurised ultrafilcration facility has a lower capital cost, resulcs indicate that an immersed ulcrafilcration facil ity has significant operation and "whole of life" (NPV) cost savings for projects greater than 6 ML/d. For an immersed ulcrafilt ration facility the estimated cost of p roduction ranged berween 53 c/kL fo r a 6 ML/d facility to 27 c/kL for a 24 M L/d facility, whilst for a pressurised ultrafilcracion faci lity it was estimated at 56 c/kL for a 6 ML/d facility to 37 c/kL for a 24 M L/d faci lity.

Keywords: Membrane Treatment Plant, ultrafiltration, microfilcration, memb ranes, effiuent reuse, wastewater reclamation, recycled water.

Introduction There is increasing interest by industry and local government au thorities in the use of membrane technology for the treatment of wastewater to p rovide high quality (Class A+) recycled water for re-use applications. The Memb rane Treatment Plant (MTP) offers the ability to produce Class A+ quality effluent, a significant advantage over conventional tertiary treatment systems. Class A+ water is suitable fo r do mestic (non-potable) reuse applications with h igh levels of human contact and a med ium risk ofingescion (QLD EPA, 2005 ). This paper will d iscuss the following:

• An overview of membrane technologies suitable for wastewater reclamation; • MTP design basis and recom mended p rocess to ensure Class A+ reuse standard; • A comparison of Zenon, Microza, NORIT, US Filter membrane technologies;

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JUNE 2006

Water

Immersed UP has higher capital, but lower operating cost, and is better for larger plants.

modular skid mounted units and higher flux rates (at the expense of higher pumping coses). Immersed systems have lower en ergy demands and are capable of handling infl uent feeds with a higher total suspended solids load.

Membranes investigated in this study A number of reputable Australian suppliers were contacted regarding membrane types. The following membrane systems were recommended: •

Zenon;

Microza;

NORIT; and

Discussion

US Filcer.

Membrane technologies

The specifications of these membrane types are summarised in Table 1. It is noted that some of the seated flux races p rovided by suppliers appear to be h igher than what GHD wo uld expect based on experience and research literature (Lozier, 2003) .

Microfiltration and ultrofiltrotion The principle of microfilcracion (MF) and ulrrafiltration (UF) is physical separation. The extent to which dissolved solids, turbidity and microorganisms are removed is d etermined by che size of rhe pores in rhe membranes and rhe integri ty of the membranes. Substances that are larger than the pores in rhe membran es are fully removed. Substances ch ar are smaller than rhe pores of the membranes are either partially removed or pass through the membrane as permeate. Membranes with a pore size of O.l - 10 µm are generally classified as achieving microfil cration (MF). Ulcrafiltration (UF) is a separation p rocess using membranes with pore sizes in che range of 0.002 to 0.1 micron. There are essentially rwo membrane treatment system co nfigu rations: •

Pressurised and

Immersed systems

Pressurised systems pump water directly into che membrane module, a housing that contains bundles of several thousands of the membrane fibres. In an immersed system the membranes are submerged in a raw tank of water and the h ead above the membrane combines with the suction draw fro m filte red water pumps. Pressurised systems have the advantage of a smaller footp rint,

Journal of the Australian Water Association

Process requirements Wastewater reclamation using m embranes is a relatively new technology in Australia. A conservative ap proach to p rocess design is recom mended to minimise the risk to the public consumers. To achieve Class A+ water it was considered that UF technology was more suitable compared to MF. MF systems have limited capacity to remove viruses (QLD EPA (a), 20 04; Kramer et al. , 2003; Metcalf and Eddy, 2003; Sakaj i, 20 0 1), and were not considered further in this study. The multi-barrier ap proach is considered a best practice app roach and is based on experience an d guidelines fro m th e fo llowing sources: • A risk management strategy to meet the Queensland Gu idelines for che Safe Use of Recycled Water (QLD EPA (a), 2004). Mr Ken H artley performed research for th is scudy. • California's Surface Water Treatment Regulations (CSWTR) which state that a water supplier is required to provide "mulcibarrier treatment" or a series of water treatment processes char provide fo r the

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Water Journal June 2006  

Water Journal June 2006