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• Disinfection (<l 500/oile and <10 maximum cfu/ l 00mL faecal coliforms, 0.20.5 mg/L Chlorine residual (dual reticulation applications), and 6 log removal of viruses and protozoa in primary settled wastewater); and

Sewage Influent

~

Conventional Activated Sludge Process

. .

Tertiary Filtration

• Filtration (Turbidity 500/oile <2 NTU and 1000/oile <5 NTU) . A suggested wastewater treatment process to achieve these objectives is as follows:

Class A+ Effluent

• Conventional activated sludge wastewater treatment plant (1-2 log removal of faecal coliforms, 1-2 log removal of viruses and protozoa, ~50-70 NTU 50%ile) . • Chlorination (3-5 log removal of faecal coliforms, > lmg/L chlorine residual, 0.5-1 log removal of vi ruses and <0.5 log removal of protozoa). • Sand Filtration (3-5 log removal of faecal coliforms, approx. 0.5 log removal of viruses and 0.5-1 log removal of protozoa, <2 NTU 500/oile). • UF (5 log removal of faecal coliforms, 2'.2-4 log removal of viruses and protozoa, <0. 1 NTU 500/oile). Ir is li kely char the above outlined process will achieve compliance with rhe gu idelin es for Class A+ recycled water. However caution must be applied due to limited publicly available operational data and guarantees for virus removal (in particular for the long term performance of UF mem branes). Authority bodies may consider an addirional barrier (such as reverse osmosis, ozonation or UV) is necessary to limit the risk to the community (and of non-compliance to Class A+ recycled water). T ertiary filtration processes such as deep sand bed filtration and cloth disc filtration are suitable pre-treatment processes. Only deep bed sand filtration (SF) has been considered in derail in chis paper. It is important to note that a conventional activated sludge process is considered necessary in combination with the MTP to ach ieve the objectives for the removal of viruses and protozoa.

MTP process unit details A MTP building housing an UF system would typically consist of the following components: • The membrane system (including skids for pressurised ultrafiltration and ranks for immersed ultrafilrrarion);

-

~

Post Chlorination

Membrane Treatment Plant

Figure 1. Recommended process requirements for a Membrane Treatment Plant to achieve C lass A+ effluent.

• Chemical dosing systems (caustic soda, sodium hypochlorire, citric acid, sodium meta bi-sulphite); and

• UF MTP (installation of membrane system to m m-key); • MT P building;

• CIP rank (IUF only). An estimated footp rint requirement fo r the MTP building housing the UF systems are given in Table 2. The footprint does not include the area required for tertiary sand filtration and an activated sludge process.

• All blowers, pumping and piping req uiremen rs;

Table 3 details che estimated footp rint requirements external to the MTP building for tertiary sand filtration, pre and post balance tanks and a pose UF storage rank. The footpr int requirements are the same for IUF and PUF.

Financial analysis A financial analysis was performed with the objective to perform a "like for like" comparison between immersed ulrrafiltration (IUF) and pressurised ultrafiltration (PUF) membrane systems. Budget estimates were developed for MTP systems with the fo llowing output capacities: • 6 ML/D; •

12 ML/D;

16 ML/D; and

• 24 ML/D. The cost esti mates presented in this section were developed for the purposes of comparing options only, not fo r render purposes. Cost estimates derailed in chis study reflect marker prices in the year 2004/05.

Capital costs

• Blower room;

The capital budget cost estimates accounts fo r the fo llowing: • Sire establishment;

• Control room;

• T ertiary Sand Filtration;

• Pumps and piping;

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54 JUNE 2006 Water Journal of the Australian Water Association

• 2x Balance ranks; • l x storage rank; • Chemical dosing/cleaning agents and storage requirements (sodium hypochlorire, citric acid, caustic soda, sodium merabisulphire); • Electrical, instrumentation and control; • Construction and installation; • T esting and commissioning; and • Contingency of 30% (1 0% engineering design and 20% construction). The capital cost estimates are summarised in Table 4.

Operating and maintenance costs The operating and maintenance budget cost estimates account fo r rhe fo llowing: • Power; • Chemicals/Cleaning agents; • Membrane and media replacement; • Maintenance (civil structures, mechanical and electrical); and • Operator input and labour. The operation budget cost estimates are summarised in Table 5.

Operation cost (c/kL) The estimated MTP operation cost (c/kL) was determined by dividing rhe annual production rate by the an nualised operation and maintenance cost in today's money. The results are presented in Table 6.

NPV analysis A 50-year NPV analysis was performed. Civil, mechanical and electrical cost

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Water Journal June 2006  

Water Journal June 2006