Removal of increasing phosphorus (P) from wastewater has become an emerging global issue as one of the main causes of eutrophication in natural waters. How does eutrophication affect human health? Why is it important to remove phosphorus from wastewater? What types of removal techniques exist? This article will discuss the urging problem of phosphorus removal from wastewater and possible WWTPs strategies. Besides, we’ll introduce an innovative solution of Transcend Water, the world leader wastewater system designing company, that recently added biological phosphorus removal (BRP) to its design functions.
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What is phosphorus removal and why is it needed?
Before answering this question, it is important to know how phosphate gets into wastewater: the main sources of phosphorus in wastewater are industrial and commercial wastewaters, human feces, and phosphorus-containing household detergents.
Phosphorus removal during wastewater treatment is crucial for public safety and environmental protection.
Here is why:
The high content of phosphorus in wastewater leads to increasing eutrophication which is a natural process that causes algal blooms. Algal blooms can stifle ecosystems, creating dead zones in which wildlife cannot survive. In addition, it causes other water quality problems that endanger our drinking water. This situation has a number of negative effects on our health: it contributes to the development of dermatological diseases and conjunctivitis, as well as diseases of the gastrointestinal tract. The increasing level of eutrophication consequently leads to an increase in morbidity.
Therefore removal of increasing phosphorus from wastewater has now become an emerging global issue.
What kind of WWTPs strategies exist to remove phosphorus from wastewater?
The removal of P from wastewater can be accomplished by chemical phosphorus removal (CPR), biological treatment (BPR), or a combination of the two:
- Chemical phosphorus removal usually involves the precipitation of the influent phosphorus with an iron or aluminum salt.
- With the BPR, increased phosphorus levels accumulate in the biological solids. Biosolids and their associated phosphorus are removed from liquid flow processes through waste-activated sludge (WAS).
How does chemical phosphorus removal work? Is it sustainable?
Chemical methods of P removal have been used for many years. However, the long-term sustainability of these technologies has not been well demonstrated, especially for the operation and maintenance of small-scale systems.
Chemical precipitation is used to remove inorganic forms of phosphate by adding coagulant and mixing wastewater and coagulant. The most commonly used multivalent metal ions are calcium, aluminum, and iron.
The procedures are generally reliable and effective, but certainly with limitations.
- some may affect the pH of the wastewater
- in many cases, the addition of chemicals is required before final discharge
- physico-chemical solutions often require additional processing steps due to the formation of foreign solids during treatment.
While this in itself does not prohibit their small-scale use, considerations should be given to options for more holistic wastewater treatment, such as biological P removal.
What is biological phosphorus removal?
Although BPR is considered to be one of the most complex processes in wastewater treatment, it has become an efficient and reliable method of nutrient removal through its widespread use in many wastewater treatment plants.
With the biological phosphorus removal method phosphorus-accumulating organisms (PAOs) can take up the organic substrate under anoxic to anaerobic conditions. Bacteria release phosphorus into wastewater to gain energy for the incorporation of the organic substrate into the microbial cell under anaerobic conditions. Once aerobic conditions are restored, the ingested organic substrate is converted to energy and cell mass. This allows the bacteria to absorb the phosphorus needed to meet their nutrient needs.
What are the advantages of BPR?
- Saves chemical addition
- Reduced sludge production compared to chemical addition
- Incorporates P into the sludge for easy removal through WAS or filtration
Innovative solution for biological phosphorus removal
Transcend Design Generator (TDG) provides a unique solution to the water sector and infrastructure industry. The SaaS application automatically integrates decisions and calculations from each engineering discipline to create a unique preliminary design of a water facility. TDG enables engineers to build many early-stage WWTP designs in 90 % less time than before.
How is this related to phosphorus removal? Well, the design generator has been recently upgraded and now includes a new function: BPR for conventional activated sludge designs.
To learn more about how TDG can support your WWTPs design, including P removal, check out Transcend Water’s website.