New Decade - New Challenges Annual Conference September 2010

Water Services Training Group

14th Annual Conference

New Decade – New Challenges9th September 2010

New Decade - New Challenges Annual Conference September 2010

Gort Waterworks Upgrade

Liam Gavin

Senior Engineer, Water Services

Galway County Council

Gort – population 3,000

Gort Water Works – built in 1930’s

Original works consisted of Raw Water balance Tank3 Slow Sand FiltersClear Water Tank

Background

Sand Filters and Raw water Tank

Issues

Historical Treated Water Quality Colour......................................... 40 – 70 mg/l Iron............................................. >0.2mg/l Manganese.................................. >0.05mg/l THM’s.......................................... >100mg/l Turbidity...................................... >1mg/l Cryptosporidium Risk Score.........167 Public Complaints Chlorine Contact Time……………. 22 mins

Operational Problems Filter capacity – 500m3/d Throughput – 1400m3/d Maintenance requirements

Proposed Gort Regional Water Supply Scheme at Preliminary Report Stage

Boil Water NoticesDue to Historical Issues Gort waterworks

was included in EPA Remedial Action List.

Issues - continued

Implement Immediate Measures Improve Chlorine Dosing Provide Chlorine Dioxide Dosing

Consultants Engaged to Carry Out Cryptosporidium Risk Assessment Develop Proposals for Short term Solution

Address Network Deficiencies Raw Water Rising Main Distribution Network Improvements

Response

Provide treated water complying with E.C. (Drinking Water ) (No.2) Regs. 2007

Reduce Cryptosporidium Risk (167 – Very High Risk Class)

Restore Public Confidence in Water Quality

Address Capacity

Statement of Need

Three options for water treatment identified

Option 1:- Upgrade existing slow sand filters

Option 2:- Construct new waterworks on new site

Option 3:- Upgrade the existing water works on the existing site.

Need to maintain existing supply.

Options

Upgrade the existing slow sand filters

Requires increased sand filter area from 120m² to 350m² to get sufficient throughput.

Insufficient space available around existing 0.16ha site. Would need to purchase an area equivalent to existing site.

Sand filtration alone not adequate to remove colour from raw water. Additional treatment processes involving coagulation and clarification would be needed.

Option 1

Construct new water works on new site

Would address all water quality issues

No site in Council ownership in Gort with suitable planning and land use matrix

Increased cost of site purchase with unacceptable delays to progress an urgent project.

Option 2

Upgrade the existing waterworks

Site very restricted for expansion or working around

Raw water balance tank – proportionally large.

Decommission and construct new units within?

Slow Sand filters undersized. Abandon and reuse? Clear water tank inadequate contact time and poor

structural condition

Option 3

Upgrade the existing waterworks

Existing site in Council ownership. Work on upgrade could proceed immediately

Use of site established and accepted.

Good location for water treatment and convenient for delivery of service to public

Option 3 is preferred option

Option 3 - continued

Original Site layout

Raw WaterTank

Clear WaterTank

Slow Sand Filter

Original Site layout

Proposed Site Layout

ControlBuilding

DAFUnit

Rapid Gravity Filters

BreakOut Wall

Wash

Water

Tank

SludgeTank

UpgradeClear WaterTank

Raw Water TankUV

Disinfection

Unit

Option 3 - Upgrade

Decommission Old

Raw Water Tank.

Construct:• New Raw Water Tank •Control Building• Flocculation Tanks •DAF Unit

Raw Water Tank

ControlBuilding

DAFUnit

Option 3 - Upgrade

Convert Slow Sand Filter No.1 to 2 Rapid Gravity Filters

Rapid Gravity Filters

New Rapid Gravity Filters

Option 3 - Upgrade

Convert Slow Sand Filter No.2 and part of No.3 to Filter Washwater Tank

Wash WaterTank

Option 3 - Upgrade

Convert part Slow Sand Filter No.3 to Sludge Storage Tank

SludgeTank

Sludge Storage

Option 3 - Upgrade

New Chemical Storage Area

Chemical Storage Area

Option 3 - Upgrade

Upgrade Clear Water Tank and address problems relating to concrete, leakage and retention time

New inlet pipeConstruct newbaffle curtains

Structural Defects

Tank Lining and Baffle Curtains

Upgrade Clear Water Tank and address problems relating to concrete defects, leakage and retention time

Drinking Water quality compliant with E.C. (Drinking Water ) (No.2) Regs. 2007

Cryptosporidium Risk reduced to < 50, Low Risk Class Raw and Treated Water Quality monitoring on site Public Confidence Condition of Structures upgraded and Leaks

eradicated Interim Solution in place until Gort RWSS is provided Plant Upgrade provided in 26 weeks

Achievements

Capital Costs

Funded under the Water Services Investment Programme by the DOEH&LG (81%) and Galway County Council (19%)

Total capital cost €760,000

€422 per m³ of treatment capacity

Costs

Operating Costs Gort Waterworks Current - €0.37/m³ before upgradeWith upgrade - €0.69/m³

Operating Costs Galway County range from €0.20/m³ - €1.50/m³

Operating Costs nationally for equivalent plant size is €1/m³

Costs - continued

Effective use of an existing resourceCompliant, safe, wholesome drinking waterCertainty of quantity and qualityValue for moneyPublic satisfaction/confidenceSupport from DOEH&LG through Water

Services Investment & Remedial Action Programmes

Summary