Tuas water plant: Ecosystem monitoring urged

NEO CHAI CHIN Today Online 11 Oct 15;

SINGAPORE — Environmental experts have recommended a slew of monitoring measures to be taken for the construction and operation of the Tuas Water Reclamation Plant, which national water agency PUB said it will review and implement progressively as construction begins in 2017.

The Tuas Water Reclamation Plant, which is part of the Deep Tunnel Sewerage System that will meet Singapore’s long-term needs for water collection, treatment, reclamation and disposal, will serve the western part of Singapore. Construction of the discharge point for treated used water — called the outfall — will begin after 2021 at Tuas Basin. The plant will handle used water from around 2024.

In an Environmental Impact Assessment (EIA) report commissioned by PUB, experts at DHI Water and Environment said the discharge of treated used water is expected to have minor to moderate negative impact on surrounding corals and seagrass, and slight negative impact on mangroves. There will also be an increased risk of algal blooms, which are of minor negative impact to overall ecology and biodiversity. These are largely due to the levels of nitrates and phosphates in the discharged water.

The good news: There will likely be no impact on marine animals such as dugongs and sea turtles.

Overall, the building of the plant is a more sustainable approach compared with a no-build scenario, as it would replace the Ulu Pandan and Jurong water reclamation plants, which use older technology, and free up land.

The EIA report, currently available for public inspection, suggested the annual monitoring of seagrass beds once the plant begins operation, given the “ecological importance of seagrass meadows in the Southern Islands and presence of internationally protected species”.

Although coral communities have been shown to adjust to local water quality and conditions, DHI suggested seasonal monitoring of coral reef conditions and nitrate levels.

A monitoring programme for phytoplankton — plankton that require sunlight to live — should also be in place to detect cells or toxins “sufficiently early”. The programme will help protect public health, fishery resources and the ecosystem structure, DHI said. Phytoplankton populations, water temperature and salinity and chlorophyll levels are among items that should be measured.

DHI found that the discharge of treated used water would be of negligible risk to fish farms around Pulau Semakau, more than 10km away.

Asked if PUB intends to adopt all mitigating measures recommended by DHI, it said the Deep Tunnel Sewerage System Phase 2 and Tuas Water Reclamation Plant project spans more than 10 years, and all proposed monitoring measures will be “reviewed and implemented progressively as the project is being developed”.

The treated used water to be discharged will be less than 35 per cent of the volume received by the Tuas plant, as the bulk is used to produce NEWater. The discharge does not include solid waste from households and industrial sources, which is extracted from used water and used to produce biogas before being incinerated.

The Tuas plant will use advanced technology, such as membrane biological reactors that greatly reduce the level of organic matter and total suspended solids in used water, compared to conventional treatment processes. This means its treated water will be of high quality.

The Tuas plant, which will result in the Ulu Pandan and Jurong plants being phased out by 2030, could adopt even more advanced technology when major upgrading is expected in 2050, noted the report.

Representatives from the Nature Society (Singapore) have seen the EIA report. Mr Stephen Beng, who chairs the society’s marine conservation group, said the EIA was comprehensive and a positive step from Phase 1 of the Deep Tunnel Sewerage System completed in 2008. An EIA was not done for Phase 1, he said.

Calling for the sharing of mitigating measures from the project’s environmental monitoring and management programme (EMMP), he said: “It’s going to be over a 25-year period. Coastal landscape and environmental conditions change, so baselines have to change as well.”

Periodic updates on the EMMP when the plant begins operations will help the public know what PUB is doing about the “growing risks of the outfall on corals and seagrass”, he added. “It’s the connected nature of the marine environment where individual stressors act in concert, resulting in cumulative effects on marine ecosystems. That’s why it requires constant monitoring.”

The executive summary of the EIA report could also be posted online to be more accessible to the public, suggested Mr Beng. The report can be viewed by appointment at the Environment Building.

The last two EIAs that PUB conducted took place in 2011 for Tuaspring Desalination Plant and this year for the third desalination plant to be built in Tuas. Both reports were open for public viewing, said the PUB spokesperson.

Currently, EIAs are required for major development projects, especially those near sensitive areas such as nature reserves and marine and coastal areas. PUB incorporates EIA recommendations in project tender specifications to ensure minimal impact and disruption to the surrounding environment, she said.

PUB did not say if every EIA report is open for public viewing. The spokesperson said: “The EIA goes through a multi-agency review before reports are gazetted and available for public viewing.”