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Best Technologies for Nutrient Removal in Wastewater Treatment
Updated: Sep 9
Overview
Nitrogen and phosphorus are needed for plant growth, but too much of them in treated wastewater can harm rivers and lakes. Treatment plants use biological, chemical and physical methods to bring these nutrients down before discharge. The right method depends on the wastewater, nutrient levels and local discharge limits. This blog explains the main technologies used for nutrient removal in wastewater treatment, including nitrification, denitrification, biological phosphorus removal and chemical treatment. It also explains how each method works, when different methods may be used together and what plant operators should check when choosing a method for nitrogen and phosphorus removal.
Table of Contents
Why Is Nutrient Removal Important in Wastewater Treatment?
To understand why nutrient removal is important in wastewater treatment, we first need to look at what happens after wastewater leaves a treatment plant.
High amounts of nitrogen and phosphorus can cause excessive algae growth in rivers and lakes. When algae die and break down, oxygen in the water can fall. This can harm fish and other aquatic life.
Good wastewater nutrient control helps reduce this problem. It may also be required for nutrient discharge compliance, depending on the discharge standards that apply to the plant.
How Does Nutrient Removal Work in Wastewater Treatment?
The answer to how does nutrient removal work in wastewater treatment depends on the nutrient being removed.
Nitrogen is often removed through biological processes. Phosphorus can be removed biologically or with chemicals.
This means nutrient removal technologies may include several treatment stages rather than one process.
Biological treatment can be supported with specialised wastewater treatment biocultures when microbial activity needs to be strengthened or stabilised.
Testing should come first. Operators need to know ammonia, nitrate, total nitrogen, phosphate and total phosphorus levels before deciding how to remove nitrogen and phosphorus from wastewater.
Nitrification and Denitrification for Nitrogen Removal
Nitrification and denitrification are widely used for nitrogen removal wastewater treatment.
Nitrification happens in the presence of oxygen. Special bacteria convert ammonia first into nitrite and then nitrate. This forms an important part of the ammonia removal process.
Denitrification takes place under anoxic conditions, where very little dissolved oxygen is present. Bacteria convert nitrate into nitrogen gas, which leaves the water.
A suitable carbon source for denitrification is also needed because denitrifying bacteria require available organic carbon.
If the wastewater does not contain enough usable carbon, an external carbon source may be considered after checking the process conditions.
Choosing the right carbon source for wastewater treatment is particularly important when biological systems require additional biodegradable carbon for denitrification.
For plants considering different dosing options, the comparison of starch vs liquid carbon source for wastewater treatment provides further guidance on carbon selection.
Enhanced Biological Phosphorus Removal
Enhanced biological phosphorus removal uses certain microorganisms to take phosphorus out of wastewater.
The process exposes the microorganisms to controlled anaerobic and aerobic conditions.
This encourages them to take up more phosphorus than they normally require. Some of that phosphorus then leaves the treatment system with the waste sludge.
This is one form of biological nutrient removal and can reduce the need for phosphorus-removing chemicals in suitable plants.
But the process needs proper operating conditions. Changes in wastewater composition, carbon availability and sludge handling can affect the result.
Chemical Phosphorus Removal
Phosphorus removal wastewater treatment can also use chemical precipitation.
Iron or aluminium salts are commonly used. These chemicals react with dissolved phosphorus and form solids. The solids can then be removed through settling or filtration.
Chemical treatment can be useful when biological removal cannot reach the required phosphorus level.
The choice between biological vs chemical nutrient removal methods should consider discharge limits, chemical use, sludge production and the existing treatment process.
Some plants use biological removal first and chemical treatment when further phosphorus reduction is required.
For an example of biological nitrogen removal in a complex industrial effluent, see this pharmaceutical ETP ammoniacal nitrogen removal case study.
Biological Nutrient Removal Systems
A biological nutrient removal process can combine nitrogen and phosphorus treatment within different zones of the treatment plant.
The biological system needs suitable pH, temperature, dissolved oxygen, sludge age and carbon availability.
Nutrient availability also matters at the microbial level, and micronutrient deficiency in wastewater treatment can affect biological activity even when the main operating parameters appear stable.
Microbial health also matters. BactaServe Nutrient Removal is a microbial culture made for wastewater treatment systems where nitrogen and phosphorus reduction is required.
A microbial culture does not replace correct plant operation. Problems with aeration, pH, retention time or organic loading should still be checked.
What Is the Best Method for Nutrient Removal in Wastewater?
There is no single answer to what is the best method for nutrient removal in wastewater.
For ammonia and nitrogen, nitrification and denitrification may be suitable. For phosphorus, plants may use enhanced biological phosphorus removal, chemical precipitation or both.
The correct carbon source for denitrification should also be considered where the wastewater does not provide enough available carbon.
Equipment selection is another consideration, and our guide to nutrient removal equipment for industrial wastewater explains the main factors to assess before choosing a treatment approach.
When selecting nutrient removal technologies, operators should check the incoming nutrient load, treatment targets, available tank space and existing plant conditions.
For industrial plants with more complex wastewater characteristics, industrial wastewater treatment biocultures can provide targeted biological support alongside the existing treatment process.
Where microbial support is required, BactaServe Nutrient Removal can form part of the biological treatment programme.
Conclusion
Good nutrient removal in wastewater treatment starts with measuring what is actually present in the water.
Nitrogen treatment commonly relies on an ammonia removal process followed by denitrification. Phosphorus removal wastewater treatment may use biological uptake, chemical precipitation or a mix of both methods.
Regular testing helps operators understand how to remove nitrogen and phosphorus from wastewater while meeting nutrient discharge compliance requirements.
The best approach to wastewater nutrient control is the one that matches the wastewater, plant design and required discharge limits.
Frequently Asked Questions
Why is nutrient removal important in wastewater treatment?
Why is nutrient removal important in wastewater treatment mainly comes down to protecting receiving waters and meeting discharge limits. Too much nitrogen and phosphorus can cause excessive algae growth.
How does nutrient removal work in wastewater treatment?
When asking how does nutrient removal work in wastewater treatment, nitrogen is commonly treated biologically, while phosphorus may be treated biologically or chemically.
What is the best method for nutrient removal in wastewater?
What is the best method for nutrient removal in wastewater depends on nutrient levels, wastewater characteristics and the required discharge standard.
What is used for nitrogen removal wastewater treatment?
Nitrogen removal wastewater treatment commonly uses nitrification to convert ammonia into nitrate and denitrification to convert nitrate into nitrogen gas.
What are biological vs chemical nutrient removal methods?
In biological vs chemical nutrient removal methods, biological treatment uses microorganisms, while chemical treatment uses added chemicals to remove certain nutrients, mainly phosphorus.
