La Mesa Water Treatment Plant; La Mesa Water Treatment Plant;

La Mesa Water Treatment Plant 1 process and structural rehabilitation, Quezon City

Improving water supply resilience of Metro Manila

Built in the 1980s, La Mesa Treatment Plant 1 is the largest water treatment plant in the Philippines with a design capacity of 1,500 million liters per day (MLD). The plant has undergone upgrading works to increase its capacity to treat turbidity in raw water and to improve resilience to handle potential earthquake related impacts.

Working with the operator, Maynilad Water Services Inc., Arup provided consultancy services for water engineering feasibility, procurement and construction management to ensure quality design and delivery of the upgrading and retrofitting works.

With the upgrades, the plant now has better water treatment capacity, automated processes and earthquake-resilient structures. Solar panels have also been included in the treatment structures to maximise treatment performance while generating renewable energy to offset the plant power usage.

Project Summary

1,500 MLD treatment upgrade

1.0MVAsolar power generation

10timesincrease in peak turbidity treatment

Developing balanced solutions

Arup undertook a feasibility study to develop the right upgrade solutions.  We assessed flow and load patterns to determine the most cost-effective and appropriate technologies, and reused existing settlement basins as much as possible through inclusion of lamella settlers.  The upgrades also maximise the operation of the existing filters through changes to the backwash system to recover this water.

Our concept design balanced the need to size for worst case conditions while allowing temporary management of sludge within basins, therefore optimising the size and cost of new assets being proposed.

Seismic retrofitting for structural resilience

Arup assessed the conditions of the existing structures through a systematic programme of site sampling.  We undertook a site-specific seismic hazard assessment, backed up by full on site cross-hole and downhole shear wave testing, to confirm the design conditions.  From this we carried out a full retrofit design for the treatment basins as well as the 3-storey administration and plant building. Fiber reinforcement is used for strengthening in parallel with concrete repairs and new concrete sections.  

The overall solution is designed to accommodate a 1 in 2475-year seismic event and allow the treatment plant to resume working quickly after an event.


Embracing renewable energy

As part of the process requirement sections needed to be covered to create better process conditions, we included solar photo voltaic panels for power generation, maximising the value of these covers. 

Our solution maximised the generation to work within Maynilad’s regulatory constraints and allowed all energy generated to be used on site.  The panels can provide 100% of the plant’s power needs during the daytime and approximately 25% of its overall energy demands, saving operating cost and carbon emissions.

Ensuring practical and safe implementation

We also developed the contract implementation process for the project, which involved upgrades of 12 operating sedimentation basins, 24 operating gravity filters, and the overall electrical and control systems. We developed a process of staged handovers and takeovers and new works and additions to allow practical and contractual management of the project.

We then led the construction implementation acting as the Engineer under the International Federation of Consulting Engineers (FIDIC) Yellow Book Contract and played an instrumental role in ensuring the safe delivery of the project with a strong focus on risk management. We regularly used global best practice to assess and develop plans for activities which interfaced with live treatment assets, reducing the risk of negative impacts on the water supply. 

As a long-term partner with Maynilad, Arup has continuously driven a better way to deliver projects – from local contracts to a merged local-FIDIC document and then the full Yellow Book application on the La Mesa project – helping the water and wastewater services provider standardise and improve ways of working.

The upgrading works was named ‘Project of the Year’ at 2022 FIDIC Contract Users’ Awards in recognition of its excellence in the use of FIDIC contract forms for project delivery and good practice through global collaboration.

More than ten million working hours have been safely delivered and through the period affected by the COVID pandemic.

The upgrades to the treatment process, and the inclusion of renewable energy generation, significantly increase the resilience of Metro Manila’s water supply and directly benefit over three million people. ” Emilfredo Siervo Senior Process Engineer, Arup