Let's talk about Solar Photovoltaic Systems in WWTPs Malaysia

In recent years, the integration of solar photovoltaic (PV) systems into wastewater treatment plants (WWTPs) has gained significant attention as a sustainable solution to address energy consumption and environmental concerns. Malaysia, with its abundant solar resources, presents a promising opportunity for the adoption of solar PV systems in WWTPs. This article explores the potential benefits, challenges, and implementation strategies for integrating solar PV systems in WWTPs across Malaysia.

Why Solar PV in WWTPs?

Wastewater treatment facilities are globally recognized as energy-intensive operations, often relying on electrical energy accounting for a significant portion of their operational expenditure (OPEX). For conventional WWTPs, energy use contributes between 25%-60% of the total OPEX Muzaffar2022 . This high dependency on the central electricity grid exposes these facilities to electricity tariffs volatility and supply uncertainties. The national sewerage company, Indah Water Konsortium (IWK) Sdn Bhd, has experienced a substantial increase with electricity costs ballooned from RM22.53 million in 2000 to RM256.30 million in 2020 IWK2021 . This became the primary motivation for IWK to explore renewable energy sources, particularly solar PV systems, to mitigate energy costs and enhance sustainability.

IWK operates as Malaysia's national sewerage company and manages a vast network of public treatment plants. As of December 2021, IWK operated and maintained 7,272 public Sewerage Treatment Plants (STPs) and 1,375 network pump stations across the country IWK2021_report . The regulatory oversight is provided by the Suruhanjaya Perkhidmatan Air Negara (SPAN), which ensures compliance with national water quality, ensuring that operators comply with stipulated standards and contractual obligations.

Energy Demand Characteristics of WWTPs

Before implementing solar PV systems, it is crucial to understand the energy demand characteristics of WWTPs to correctly sizing and optimizing a solar PV system. The energy consumption profile of WWTP is highly influence by the pkant scale and the dominant treatment technology used.

Specific Energy Consumption (SEC) and Categorization

Energy intensity, generally measured as Specific Energy Consumption (SEC) in kilowatt-hour per cubic meter (kWh/m³) of treated wastewater, is a key metric for evaluating the energy efficiency of WWTPs. The SEC values can vary significantly based on the treatment processes employed and the plant's capacity. Data suggests that smaller WWTPs, particular those below $10,000 m^3/month$ capacity, tends to bear a disproportionately higher electricity cost, accounting for 30%-40% of their total running costs Muzaffar2022 . In contrast, larger WWTPs with capacities exceeding typically exhibit lower SEC values, accounting for 15%-30% of the total running costs.

Specific data collected from village WWTPs in Romania indicated high annual average SEC values, ranging between $1.786 kWh/m^3$ to $2.334 kWh/m^3$ of treated wastewater Tokos2021 . Furthermore, the complexity of sewage sludge disposal capacity has increased rapidly alongside population growthm reaching 7 millions $m^3$ annually. Managing this sludge requires significant energy input, contributing to the sector's overall energy consumption, with sewage sludge treatment alone consuming an estimated $544,900 GWh$ across IWK operations between 2016 and 2019 Quan2022 .

This observed variability indicates that the primary candidates for immediate solar PV intergartion are the small to medium sized conventional STPs. These plants have higher SEC values and higher dependence on expensive grid power, meaninf the marginal return from solar PV energy offset is maximized in this segment.

Identification of Energy-Intensive Processes

The greatest energy concentration of electrical energy demand within a conventional WWTP is typically found in the biological treatment line (BgT), primarily driven by the aeration systems. This process is necessary for activated sludge processes to maintain adequate dissolved oxygen levels for microbial activity. Data confirms that BgT accounts for the majority of total energy consumption, ranging from 63.2% to 72.9% in surveyed WWTPs Tokos2021 .

Whether thorugh diffused air of mechanical aerators (such as those used in oxidation ditches), aeration systems requires continuous operation to provide oxygen transfer, circulation, and mixing. This need for continuous, high-power during daytime operational hours, and we realized this characteristic is highly advantageous for solar PV integration. The steady daytime demand for blowers and aerators means that the generated solar power can be immediately and entirely consumed, leadning to high utilization rates, and diminish the need for Battery Energy Storage Systems (BESS), which is often a significant cost driver in renewable energy (RE) projects.

The high concentration of energy use in aeration suggests that before implementing solar PV systems, WWTP operators should measures energy efficiency in the aeration systems. Simply installing a large PV array without optimzing the blowers and biological processes may lead to a larger and more costly system. Streamlining the anaerobic biological treatments is possible and should be prioritized to reduce the overall energy demand before sizing the solar PV system.

Advanced PV Power Forecasting and Control Systems

The modern integration of photovoltaic systems into WWTPs requires sophisticated forecasting and control architectures. Recent research demonstrates a clear evolution toward hybrid AI-based forecasting models that combine deep learning with optimization algorithms IturraldeCarrera2025 . These advanced models significantly outperform classical deterministic methods in handling the highly dynamic and non-linear conditions of real-world PV generation.

Machine learning ensemble algorithms such as XGBoost, LightGBM, and CatBoost have emerged as foundational tools for high-accuracy solar power prediction Nguyen2025 . A critical finding is that humidity and ambient temperature emerge as the most influential factors affecting PV module efficiency, particularly in tropical and humid climates.

Integrated Energy Management

Effective PV system integration requires a multi-layered control hierarchy. The foundational layer is Maximum Power Point Tracking (MPPT), which continuously adjusts the DC-DC converter to extract maximum available power from the solar array. A critical technical constraint in many jurisdictions is the Zero Export requirement, which prohibits injecting electrical power back into the grid. To comply, Zero Export Controllers (ZEC) operate on near-instantaneous feedback loops Alnawafah2025 .

Battery Energy Storage Systems provide flexibility to address both PV intermittency and zero-export constraints. Advanced control algorithms optimize charging during low-cost periods and discharging during peak tariff hours Hvala2025 .

Conclusion

The successful integration of solar PV systems into Malaysian WWTPs needs a strategic of advanced forecasting. By combining accurate generation forecasting with sophisticated demand-side prediction, facilities can achieve near energy-autonomous operation while positioning themselves as flexible power assets responding to grid demands.

In the future research we need to explore the details implementation of predictive modelling and control algorithms in WWTPs, as well as conducting in-depth literature reviews on case studies of existing energy predictive systems in WWTP.