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A positive impact on everything we touch
Over 1800 dedicated people nationwide
Providing critical infrastructure for the UK
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Yorkshire Water Services Limited

Caustic and Lime Plant.

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New Lime Preparation and Dosing Plant for the first stage pH correction (Pre-RGF) and a Sodium Hydroxide System with associated Water Softener System for the final pH correction.

Design development, optioneering and detailed design and construction of Caustic and Lime Plant.

Headingley WTW had a DWI Improvement notice issued for Turbidity which had to be achieved by December 2016. The existing Lime Dosing plant was old and was not operating correctly.

Furthermore, the Lime plant was non-compliant to Yorkshire Water’s standard. nmcn was commissioned in February 2016 to replace the existing Post-RGF Lime Dosing plant with a new specification compliant solution and replace the pre-RGF Lime Dosing plant with 47% Sodium Hydroxide.

Key Information

Project

Caustic and Lime Plant.

Client

Yorkshire Water Services Limited

Delivery Division

Water

Value

£1.8m

Date

May 2016 - May 2017

Benefits at a Glance

nmcn co located with Yorkshire Water
Delivered 3 months early
No impact to existing operations

Challenge:

The project scope included:

Design, procure, install and commission a 47% Sodium Hydroxide package plant to be suitable for permanent final pH correction and also to provide a temporary chemical dosing system for the first stage (pre RGF) pH correction during construction and commissioning of the Lime Preparation and Dosing Plant.

The final water pH correction system was designed for the following process parameters:

  • final pH range between 6.7 to 7.4
  • works flow rates between 65 Mld and 120 Mld
  • works average flow rate of 80Mld
  • dilution factor with softened water –8:1 Minimum
  • dosing rate range – 3 mg/l to 55 mg/l as 47% solution (i.e. 1.4 mg/l to 25.9 mg/l as NaOH)

The temporary first stage (pre-RGF) pH correction system was designed for the following process parameters:

  • intermediate pH range between 6 to 7
  • works flow rates between 65 Mld and 120 Mld
  • works average flow of 80Mld
  • dilution factor with softened water –8:1 Minimum
  • dosing rate range to be equivalent to 2.0mg/l to 45mg/l as 100% Lime.

 

 

Water Softener System

  • To design, procure, install and commission a new Water Softener System suitable for the Sodium Hydroxide system, which is to be located in the PAC room.
  • The system was designed for the following process parameters for ❍ Dilution ratio for Sodium Hydroxide = 8:1 minimum ❍ 40 l/hr to a maximum of 1,500 l/hr

Static Mixer

  • Like for like replacement of the static mixer at the point of application for final pH correction including suitable dosing application,  lime preparation and dosing plant
  • To design, procure, install and commission a lime preparation and dosing plant, which is inclusive from the lime transfer system to the point of application (pre RGF). This does not include silo outlet agitation or any other work to the lime bulk storage silos or lime delivery system.

The lime preparation and dosing plant were designed to the following specifications:

  • works flow rates between 65 Mld and 120 Mld
  • dose rates 2 mg/l to 45 mg/l as 100% Lime
  • designed to provide lime slurry to the pre Flocculation and pre RGF
  • each batch tank capacity at 120Mld, 2% Slurry and 45mg/l

Solution:

The overall programme for this project was very tight, alongside which we needed to maintain pH correction for the duration of the works. We held regular reviews with all the relevant stakeholders of Yorkshire Water and identified that we could build the Sodium Hydroxide plant with dual duty/standby dosing cabinets which would be used to dose pre and post RGF.

Results:

nmcn were able to manufacture the new Sodium Hydroxide Plant using our in-house Offsite Build Facility. The plant was delivered to site and commissioned by the end of September 2016, 3 months ahead of the regulatory date.

Not only did this meet the commitments Yorkshire Water had with the DWI, but it also allowed the entire lime plant to be completely decommissioned so we could remove the old and install the new plant without having to manage the upgrade works around live commissioned equipment. Therefore there was also an added benefit of removing the risk of our works impacting on the operations of the plant.

Testimonials

A job well done - please offer our thanks to all your guys

Senior Engineer - Yorkshire Water

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