Mainly in low-income areas, a large proportion of the wastewater is discharged directly in the environment. When the wastewater is treated, the treatment plants may not remove certain pollutants that can have a negative impact on the people and ecosystem. Treated wastewater usually contains high levels of nutrients that can cause algae blooms on the water surface of storage ponds. The treatment of algae in waste water lagoons is important to improve the water quality before discharge.
Algae growth in stabilization ponds
An important issue to consider in wastewater reuse and treatment is algae growth, which is relatively common in warm and nutrient-rich waters. Treated wastewater usually contains high levels of nutrients that can cause algae blooms on the water surface of storage ponds and clog irrigation systems (ﬁlters, emitters, distribution pipes). Furthermore, some freshwater algae can form harmful algal blooms (HABs), and these speciﬁc species create health hazards for humans and animals by producing toxins and bioactive compounds that deteriorate the water quality.
Although there are several methods to treat wastewater, this article focuses on stabilization ponds (also called lagoons or waste stabilization ponds). These types of ponds and lagoons consist of in-ground earthen basins in which the waste is detained for a specified time (retention time) and then discharged. The size and depths can vary, as well as the degree of treatment. Lagoons are typically classified by their degree of mixing and amount of oxygen dissolved in the water.
Examples of lagoons are anaerobic lagoon, facultative lagoon, aerobic lagoon, partial-mix aerated lagoon, and completely mixed- aerated lagoon.
Controlling algae in wastewater before discharge
1. Compliance with wastewater quality standards
One of the Sustainable Development Goals (SGD) is to improve the water quality by halving the proportion of untreated wastewater. Globally, over 80% of the wastewater generated by society flows back into the ecosystem without being treated or reused (Sato et. al, 2013).
The Clean Water Act of 1970, and the Federal Water Pollution Control Act Amendments of 1972, established the National Pollutant Discharge Elimination System or NPDES is an effort to assure that wastewater discharges would not adversely affect aquatic recreation or wildlife.
The NPDES permit identifies monthly averages and maximum levels of BOD, Suspended Solids, and Fecal Coliform allowed in the treatment plant effluent. In larger systems, and systems that discharge into sensitive surface waters or groundwater supplies, NPDES permits may also require removal of nitrogen and phosphorous.
2. Lower Biochemical Oxygen Demand (BOD) Levels
BOD is an indicator of the biological pollution of water. Industrial waste water is characterized by high BOD levels. Increasing water supply and disposal prices, together with increased environmental regulations, require environmentally-friendly and cost-effective solutions to treat waste water before discharge.
If these organics are not stabilized in the treatment process, there will be dissolved oxygen depletion from the receiving water. This oxygen depletion can result in fish kills and damage to the aquatic ecosystem.
3. Lowering the amount of Total Suspended Solids (TSS)
TSS include all particles suspended in water which will not pass through a filter. In terms of water quality, high levels of total suspended solids will increase turbidity and decrease dissolved oxygen (DO) levels. This can affect the operation process.
MPC-Grid is developed by LG Sonic to increase the quality of treated wastewater in stabilization ponds and facultative lagoons. Algae can grow in wastewater whilst its being treated, and decrease the quality of the treated water. This means that treated wastewater will not comply with the waste water quality standards to reenter the environment.
MPC-Grid controls and monitors the algae to have higher quality water that is safe to release back in the environment. Besides controlling the algae growth, the system allows to reduces BOD, TSS and pH levels. The MPC-Grid has a monitoring system which provides real-time the water quality data in the lagoon.