Incident Pond: Concept and Role in Wastewater Treatment System

In the context of increasing demand for wastewater treatment, building a standard treatment system is a mandatory requirement for industrial zones and production facilities. In addition to main treatment structures such as sedimentation tanks, biological tanks, or disinfection units, auxiliary facilities also play a key role in maintaining the stability and safety of the entire system. One important yet often overlooked structure is the emergency pond, which serves as a “backup” when the system encounters unexpected problems. Let’s explore this in detail with the following content.

1. Emergency pond in a wastewater treatment system

The emergency pond in a wastewater treatment system is an auxiliary facility designed to temporarily receive and store excess or sudden wastewater generated during operation. This is an important component that protects downstream treatment structures, preventing overload, equipment damage, or the discharge of untreated wastewater into the environment. In essence, the emergency pond functions as a “safety buffer zone,” giving the system more time to adapt and treat wastewater effectively during incidents.

Besides regulating flow, the emergency pond also helps minimize environmental pollution risks in case of malfunctions in main treatment stages. In some systems, it is combined with preliminary treatment measures such as sedimentation or disinfection to reduce pollution load before re-entering the system. Thanks to this function, the emergency pond is considered a mandatory backup solution under many current wastewater treatment plant design standards.

What is an emergency pond in a wastewater treatment system?

2. Main functions of the emergency pond

• Regulating wastewater flow and concentration: The emergency pond balances influent flow, preventing sudden fluctuations that could affect treatment efficiency. It also helps equalize pollutant concentrations, ensuring more stable performance in downstream units.
• Temporary storage during incidents (heavy rain, overload, equipment failure): Under abnormal conditions such as heavy rainfall, equipment malfunction, or power outage, the pond serves as a temporary reservoir. This allows time for repairs and prevents direct discharge into the environment.
• Reducing the load on downstream structures: When the system is overloaded, the emergency pond receives part of the wastewater, lowering the pressure on sedimentation tanks, biological tanks, or subsequent treatment units. This prevents performance loss or equipment damage caused by overcapacity.
• Preventing environmental pollution during incidents: The pond acts as the final safety barrier, stopping the release of untreated wastewater into the environment during emergencies. This is a reliable solution to minimize negative impacts on receiving waters and surrounding ecosystems.

3. Location and design of the emergency pond

3.1 Placement in the treatment process flow

The emergency pond is usually located after preliminary treatment units such as screens and grit chambers, and before main biological treatment units. This placement allows it to directly receive wastewater during incidents or sudden inflow surges, while protecting downstream tanks from overload. In some systems, the emergency pond may also be placed at the end of the line as a “buffer zone” to block untreated wastewater from escaping into the environment.

3.2 Design principles (capacity, retention time, structure)

When designing an emergency pond, its capacity must be calculated to accommodate wastewater generated under worst-case scenarios such as prolonged heavy rain or total system failure. Retention time is typically set long enough to minimize temporary pollution impacts and allow additional treatment if necessary. Structurally, the pond must have proper anti-seepage measures, flexible inlet–outlet systems, and monitoring equipment to ensure safe operation.

4. Regulations on emergency pond construction in wastewater treatment

According to the Law on Environmental Protection 2020 (Article 99) and its guiding documents, emergency ponds are mandatory in many centralized wastewater treatment systems, especially for industrial zones and facilities with high pollution risks. These ponds are required as a preventive measure to ensure untreated wastewater is not directly discharged into receiving waters.

Furthermore, Decree 08/2022/ND-CP clearly stipulates that wastewater treatment system owners must have backup facilities or preventive measures, with emergency ponds being one of the most common and effective solutions.

Additionally, in QCVN 40:2011/BTNMT – National Technical Regulation on Industrial Wastewater, the Ministry of Natural Resources and Environment emphasizes that emergency ponds must be designed with sufficient capacity to store wastewater in case of incidents, avoiding direct discharge into the environment. The pond must also be impermeable, equipped with collection and monitoring systems, and ensure operational safety. These legal foundations help enterprises and industrial zones comply with regulations, minimize risks, and reduce legal liability during environmental incidents.

Regulations on emergency ponds under current QCVN standards

The emergency pond is not just an auxiliary structure but a safety shield for the entire wastewater treatment system. With its functions of regulation, storage, and protection, it minimizes the risk of polluting discharges. Moreover, proper construction and operation of emergency ponds in compliance with standards help enterprises and industrial zones meet legal requirements, reduce economic losses, and affirm their commitment to sustainable development.