An Overview of Sustainably Removing Biological Nutrients from Municipal Wastewater

July 30, 2020

There has been a strong movement over the last couple of decades to find more sustainable processes for removing biological nutrients in municipal wastewater in Missouri and beyond. The goal is to use more energy-efficient and water-conserving processes without compromising the quality of wastewater management and treatment.

The primary forms of nutrient enrichment due to human activities in surface waters are nitrogen and phosphorus. The most common symptom of this issue is the algal blooms that occur during the summer. If water gets overly enriched, it can have issues with low dissolved oxygen, murky water and depletion of desirable plant and animal life.

From a wastewater standpoint, then, it is important to take the necessary biological nutrient removal steps in Missouri before the water is released back into natural waterways or into municipal water systems.

Nitrogen removal

Total effluent nitrogen comprises substances such as nitrate, ammonia, soluble organic nitrogen and particulate organic nitrogen. The processes that must be used to remove nitrogen from wastewater are nitrification and denitrification.

During the process of denitrification, ammonia gets oxidized to nitrite by autotrophic bacteria, usually Nitrosomonas. The nitrite then gets oxidized to nitrate by another bacteria group, usually Nitrobacter. The denitrification process also involves the reduction of nitrate to nitric oxide, nitrous oxide and nitrogen gas.

Nitrification is a process implemented to help maintain control over the treatment, as ammonia oxidizing bacteria do not have sufficient functional diversity, have some strict growth requirements and are highly sensitive to certain types of environmental conditions. While nitrification on its own will not remove nitrogen from wastewater, it does coordinate with denitrification to resolve the issue. It occurs in the presence of oxygen in aerobic conditions, while denitrification occurs in the absence of oxygen under anoxic conditions.

Phosphorus removal

Efficient phosphorus removal is also important to create properly treated water. Total effluent phosphorus features both soluble and particulate phosphorus, the latter of which can be removed simply through solids removal. It is the removal of soluble phosphorus that is more difficult, but it must be accomplished if low effluent concentrations are to be achieved.

The process of biological phosphorus removal relies on phosphorus uptake via aerobic heterotrophs that are capable of storing orthophosphate greater than their biological growth requirements. Efficient treatment processes are those that are designed to ensure maximum growth of phosphate-accumulating organisms (PAOs).

In anaerobic conditions, those PAOs will convert organic matter into carbon compounds. PAOs will use the energy created through the breakdown of polyphosphate molecules to create those carbon compounds, a process that results in the release of phosphorus.

In aerobic conditions, the PAOs will use those stored carbon compounds as energy to take up any phosphorus released in the anaerobic conditions, plus additional phosphate that still remains in the wastewater.

If you’re interested in learning more about the steps municipal water treatment facilities can take to create more environmentally-friendly and efficient wastewater treatment systems through biological nutrient removal in Missouri, we encourage you to contact Enviro-Line Co., Inc. today. We look forward to answering your questions!

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