Pax Silica’s Water Demand Poses Major Challenge Amid Central Luzon’s Drought Risks

Pax Silica, a planned semiconductor and artificial intelligence hub in New Clark City, Tarlac, faces significant water security challenges that could affect both the project and surrounding communities. The industrial complex is projected to require 130 million liters of water daily, equivalent to the irrigation needs of thousands of hectares of rice land, underscoring the scale of its water demand in a drought-prone region.

The Bases Conversion and Development Authority (BCDA) has stated that the project will not tap groundwater but will rely on rainwater harvesting and reservoir construction. However, an analysis of local rainfall patterns, reservoir capacity, construction costs, and wastewater recycling indicates that rainwater alone will be insufficient to meet Pax Silica’s needs, especially during El Niño years when rainfall can decline by 40% to 60%.

Tarlac receives an average annual rainfall of 1,761 millimeters, but precipitation is highly seasonal. Peak months from June to September see 237 to 324 millimeters of rain, while dry months from February to April receive less than 30 millimeters. Under normal conditions, the 1,600-hectare Pax Silica site could theoretically capture about 28 billion liters of rainwater annually, which is 11 billion liters short of the 39 billion liters annual requirement used in the analysis. During El Niño years, rainfall capture could drop to approximately 17 billion liters, increasing the deficit to 22 billion liters.

To store the required 39 billion liters annually, reservoirs would need to cover between 390 and 780 hectares of the site, depending on depth. At an average depth of 5 meters, about 780 hectares would be required, while increasing depth to 10 meters could reduce the land needed to 390 hectares but would raise engineering and safety risks. This means that 25% to 50% of the 1,600-hectare site would be dedicated to reservoirs, creating significant land-use trade-offs with industrial development, agriculture, and community spaces.

Reservoir construction costs are substantial. A small 50-hectare reservoir could cost between P825 million and P2.75 billion, while a large 780-hectare reservoir might cost between P55 billion and P110 billion. Lining reservoirs to prevent seepage would add an estimated P2.1 billion to P4.3 billion. Annual maintenance costs, including desilting, pumping, and treatment, could add another P1 billion to P2 billion. These figures exclude the opportunity cost of land that could otherwise be used for other purposes.

Given the limitations of rainfall capture and reservoir storage, wastewater recycling emerges as a critical component to reduce freshwater demand. Semiconductor manufacturing centers in Taiwan, South Korea, and the United States have demonstrated that significant water recovery is possible. Taiwan Semiconductor Manufacturing Co. (TSMC) achieves recycling rates above 88% to 90%, while Samsung and SK Hynix in South Korea recycle about 40% to 47%.

For Pax Silica’s projected daily demand of 130 million liters, advanced recycling systems capable of recovering 85% to 95% of wastewater could allow reuse of approximately 110 million to 124 million liters daily. This would reduce net freshwater intake to between 6 million and 20 million liters per day. However, such recycling requires advanced treatment technologies to remove heat, heavy metals, fluorides, and toxic organic compounds found in semiconductor wastewater. These include membrane bioreactors (MBR), reverse osmosis (RO), advanced oxidation processes (AOP), and zero liquid discharge (ZLD).

The treatment process begins with cooling and equalization tanks to stabilize wastewater flow and temperature, followed by MBR to remove suspended solids and organic matter, achieving chemical oxygen demand reductions of 92% to 97%. RO then removes 90% to 95% of dissolved salts, fluorides, and metals. AOP breaks down refractory organic compounds such as tetramethylammonium hydroxide (TMAH). ZLD, the highest treatment level, uses evaporation and crystallization to recover 95% to 99% of water, leaving solid waste for disposal.

Implementing these advanced recycling systems entails significant capital and operating costs. MBR-RO hybrid systems may cost $3 million to $10 million per semiconductor fabrication plant, while full ZLD systems require $15 million to $50 million in capital expenditures. Operating costs, driven by energy use and membrane replacement, range from $0.50 to $2 per cubic meter treated. For Pax Silica, annual ZLD operating costs could reach P800 million to P2 billion, totaling P16 billion to P40 billion over 20 years and potentially rising to P40 billion to P100 billion over 50 years.

Capas, Tarlac, where Pax Silica is located, is hydrologically connected to the wider Central Luzon water system, including the Tarlac and Agno Rivers. Reservoir construction must consider heavy runoff and lahar-related siltation from Mount Pinatubo, requiring reinforced embankments, sediment management, and lining to prevent seepage. Without adequate lining, seepage losses could reach 20% to 30%.

In summary, Pax Silica’s water security strategy combining rainwater harvesting, extensive reservoir construction, and advanced wastewater recycling involves estimated upfront costs of P60 billion to P115 billion for reservoirs and P825 million to P2.75 billion for recycling infrastructure. The integrated cost over 20 to 50 years could range from P76 billion ($1.38 billion) to P215 billion ($3.91 billion). While Taiwan’s semiconductor industry has absorbed similar investments supported by strong state subsidies, these costs raise questions about economic viability and the trade-offs among industrial development, agriculture, and potable water supplies in the Philippines.