In wastewater treatment projects, excessive total nitrogen (TN) is one of the most common and difficult problems to solve through a single process alone. Total nitrogen is not a single pollutant, but a comprehensive indicator of multiple nitrogen-containing substances in a water body, usually including organic nitrogen, ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen.
When influent water quality fluctuates significantly, carbon sources are insufficient, dissolved oxygen (DO) control is unreasonable, or the sludge age and sludge load of the biochemical system are not effectively controlled, the effluent total nitrogen may still fluctuate even if indicators such as COD and BOD have met the requirements.
Therefore, determining how to handle excessive total nitrogen in wastewater treatment cannot be simply understood as adding a chemical agent or adding a stage of filtration; instead, it requires analysis starting from influent water quality, nitrification conditions, denitrification conditions, and the overall process flow.
For industrial wastewater, food wastewater, chemical wastewater, and other projects that require strict control of nitrogen pollutants, establishing a reasonable total nitrogen removal system is an important link to ensure stable compliance discharge and improve water resource utilization rates.
1. What is Total Nitrogen? Why Does Wastewater Total Nitrogen Need Key Control?
Total Nitrogen (TN) is an important water quality indicator used to measure the degree of nitrogen pollution in wastewater.
From the perspective of composition, total nitrogen mainly involves:
Organic nitrogen
Ammonia nitrogen
Nitrite nitrogen
Nitrate nitrogen
In traditional biochemical wastewater treatment systems, nitrogen undergoes different transformation processes. A typical biological nitrogen removal process can be simply understood as: Organic nitrogen → Ammonia nitrogen → Nitrite / Nitrate → Nitrogen gas
Among them, the nitrification stage is mainly responsible for gradually oxidizing ammonia nitrogen into nitrate, while the denitrification stage utilizes denitrifying microorganisms to reduce nitrate into nitrogen gas, thereby achieving true total nitrogen removal.
Therefore, if there is only nitrification without sufficient denitrification, even if ammonia nitrogen has dropped significantly, nitrate may still accumulate in the effluent, ultimately causing the total nitrogen indicator to exceed standards.
2. What Impacts Does Excessive Wastewater Total Nitrogen Bring?
1. Affecting Wastewater Discharge Compliance
The "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918-2002) stipulates that the total nitrogen concentration for Class A standards must not exceed 15 mg/L, and for Class B standards must not exceed 20mg/L.
Therefore, during actual operation, if the effluent total nitrogen is consistently higher than the design or discharge requirements, it may lead to the wastewater failing to meet standards stably. For enterprises, this not only increases environmental management pressure but may also further affect production operations.
Standard data from the original materials clearly points out that the total nitrogen limit for Class A standards is 15 mg/L, and for Class B standards is 20mg/L.
2. Increasing the Risk of Water Eutrophication
Nitrogen-containing pollutants entering natural water bodies may promote the massive proliferation of algae and further alter the dissolved oxygen balance in the water body.
When algae and other organic matter increase significantly, the microbial decomposition process may consume a large amount of oxygen, thereby affecting the aquatic ecological environment.
Therefore, the causes and treatment methods for excessive wastewater total nitrogen are not only related to whether enterprise discharges are compliant, but also closely related to water environmental protection.
3. Impacting Water Reuse
For projects requiring reclaimed water reuse, process water reuse, or other water resource recycling, total nitrogen is also one of the water quality parameters that needs attention.
If the total nitrogen removal capacity of the front-end biochemical system is insufficient, the subsequent advanced treatment system may need to bear a larger treatment load.
Therefore, when designing advanced wastewater treatment systems, complete biological nitrogen removal should ideally be completed at the front end, followed by the selection of membrane treatment, filtration, or other advanced treatment processes based on final water quality requirements.
3. Main Causes of Excessive Total Nitrogen in Wastewater Treatment
1. Excessively High Organic Nitrogen and Ammonia Nitrogen Loads
When the concentrations of organic nitrogen and ammonia nitrogen in the influent are high, while the treatment capacity of the biochemical system is insufficient, the nitrification process may not be fully carried out.
Nitrifying microorganisms usually require stable dissolved oxygen, suitable temperatures, and sufficient sludge age. If these conditions are insufficient, ammonia nitrogen cannot be fully converted into nitrate, which affects the entire nitrogen removal process.
2. Insufficient Carbon Sources, Restricting Denitrification
This is a problem worthy of attention in actual projects.
The denitrification process requires carbon sources as electron donors. When wastewater passes through front-end biochemical treatment, biodegradable organic matter has already been largely consumed, while nitrate concentrations remain high, denitrifying microorganisms may fail to complete denitrification due to a lack of sufficient carbon sources.
The final manifestation is: Ammonia nitrogen drops, but nitrate is not fully removed → Effluent total nitrogen remains high.
Therefore, when analyzing industrial wastewater total nitrogen excess treatment schemes, one should not only test ammonia nitrogen, but also comprehensively judge based on indicators such as nitrate, COD, BOD, and biodegradable carbon sources.
4. Why Does Dissolved Oxygen Affect Total Nitrogen Removal?
1. The Nitrification Stage Requires Appropriate Dissolved Oxygen
Nitrification is an aerobic biological process.
If aeration is insufficient and dissolved oxygen is too low, the activity of nitrifying microorganisms will decline, ammonia nitrogen cannot be fully oxidized, and ultimately ammonia nitrogen and total nitrogen may be high at the same time.
2. The Denitrification Stage Requires a Relatively Anoxic Environment
The environmental conditions for denitrification and nitrification are different.
If the dissolved oxygen in the denitrification zone is excessively high for a long time, it may affect the ability of denitrifying microorganisms to utilize nitrate for reduction reactions.
Therefore, reasonably controlling the operating conditions of aerobic zones and anoxic zones is an important foundation for stable biological nitrogen removal.
5. Temperature, Sludge Load, and Sludge Age May Also Lead to Excessive Total Nitrogen
The original materials indicate that excessively low wastewater temperatures, excessively high or low sludge loads, and excessively short or long sludge ages may all affect the nitrification and denitrification processes.
Temperature: Temperature directly affects the growth and metabolic rates of microorganisms. Under low-temperature conditions, the activity of nitrifying microorganisms is usually affected, so the stability of the nitrification system needs special attention during winter operation.
Sludge Load: Excessive changes in sludge load will lead to changes in the microbial community and operating status within the biochemical system.
Sludge Age: Nitrifying microorganisms grow at a relatively slow rate, thus requiring a sufficient sludge age to maintain effective flora in the system. If the sludge age is too short, it may cause the loss of nitrifying bacteria, thereby reducing ammonia nitrogen oxidation capacity.
This is why judging how to handle excessive total nitrogen in wastewater treatment requires simultaneously reviewing operating parameters rather than looking only at a single effluent test result.
6. What Treatment Methods Exist for Excessive Wastewater Total Nitrogen?
Depending on the wastewater quality, treatment scale, discharge requirements, and existing processes, different nitrogen removal technology routes can be adopted.
Method 1: Biological Nitrogen Removal
Biological nitrogen removal is a relatively common treatment route in wastewater treatment.
Its core is utilizing microorganisms to complete the nitrification and denitrification processes, ultimately converting nitrogen-containing pollutants in the wastewater into nitrogen gas.
Common process forms include:
Biofilm process
Biological filter
A/O and A²/O class biological treatment processes
Other enhanced biochemical nitrogen removal processes
Ecological treatment methods such as constructed wetlands
The original materials also list methods such as the biofilm process, biological filters, and constructed wetlands, and point out that such methods may have characteristics such as complex processes, high operational requirements, large footprints, and long operating times.
In actual engineering, if the existing system already possesses biochemical treatment conditions, priority can be given to analyzing whether total nitrogen removal effects can be improved by adjusting the reflux ratio, aeration, sludge age, carbon sources, and anoxic section operating conditions.
7. The Role of Physical and Advanced Treatment Technologies in Total Nitrogen Control
In addition to biological treatment, advanced treatment technologies such as membrane treatment and ion exchange can also be adopted according to project requirements.
Membrane treatment can further reduce the concentration of certain pollutants in water through membrane separation, but for specific total nitrogen composition, process selection needs to be based on the actual concentrations of ammonia nitrogen, nitrate nitrogen, and other nitrogen-containing substances.
The original materials propose that physical nitrogen removal methods include membrane treatment technology, chlorination, and ion exchange technology, and point out that some methods may have problems such as high operating costs and the generation of concentrated liquid or other by-products.
Therefore, advanced treatment does not necessarily mean simply adding equipment, but rather determining technology combinations based on actual water quality.
8. ECOLINK TECHNOLOGY Nitrogen Removal Equipment Solutions
For projects where effluent total nitrogen is difficult to stably meet standards, ECOLINK TECHNOLOGY can match corresponding water treatment equipment and process schemes according to the customer's raw water quality, treatment volume, and discharge requirements.
The ECOLINK nitrogen removal equipment in the original materials adopts reverse osmosis technology combined with biological nitrogen removal technology to enhance total nitrogen treatment, and features characteristics such as small equipment volume, small footprint, stable operation, and simple operation.
1. Scheme Matching Based on Water Quality
Wastewater from different sources may have completely different total nitrogen compositions.
For example:
Wastewater with a high proportion of ammonia nitrogen requires a focus on nitrification capacity;
Effluent with a high proportion of nitrate requires a key analysis of denitrification conditions;
Low C/N ratio wastewater requires attention to whether carbon sources are sufficient;
High-concentration industrial wastewater requires comprehensive consideration of toxicity, salinity, temperature, and organic load.
Therefore, ECOLINK TECHNOLOGY focuses more on process matching starting from actual water quality rather than simply recommending a single piece of equipment.
2. Compact Equipment, Small Footprint
For existing wastewater treatment plant upgrade and renovation projects, spatial footprint is often an important limiting factor.
The original scheme proposes that the equipment has a small volume and small footprint, and can be customized according to customer needs.
Such schemes are particularly suitable for projects that need to add total nitrogen removal equipment on the basis of original wastewater treatment systems.
3. Relatively Simple Operation
Wastewater treatment equipment not only needs to achieve designed treatment effects, but also needs to consider long-term operation and maintenance.
The original materials propose that the equipment operates stably and is simple to operate, and can be mastered without professional technical personnel.
In actual projects, ECOLINK TECHNOLOGY can provide corresponding technical data, operating instructions, and project support based on equipment configurations.
4. Total Nitrogen Removal Rate Up to 99%
The professional nitrogen removal equipment in the original materials proposes that the total nitrogen removal rate can reach 99%.
It should be noted that the final treatment effect of actual projects is still related to influent water quality, pollutant concentration, operating conditions, treatment scale, and system design, so engineering schemes should be confirmed based on actual water quality analysis and site conditions.
9. Wastewater Treatment Total Nitrogen Excess Case Studies
Case 1: Chemical Plant Total Nitrogen Reduced from 50mg/L to Below 5 mg/L
The total nitrogen concentration of the wastewater treatment system of a certain chemical plant reached 50mg/L, which is higher than the national emission standard of 20mg/L.
Aiming at the wastewater characteristics and treatment demands of this project, ECOLINK provided a professional nitrogen removal equipment scheme, adopting reverse osmosis technology and biological nitrogen removal technology for treatment.
After treatment, the wastewater total nitrogen was reduced to below 5mg/L, reaching the Class A standard.
This case illustrates that when traditional biochemical systems cannot stably control total nitrogen, effluent water quality can be improved by adding targeted advanced treatment units.
Related original case data: influent total nitrogen 50mg/L, treated below 5mg/L.
10. Food Plant Total Nitrogen Reduced from 40mg/L to Below 10mg/L
The total nitrogen concentration of the wastewater treatment system of a certain food plant reached 40mg/L, higher than the national emission standard of 20mg/L, while affecting wastewater discharge and reuse.
ECOLINK configured nitrogen removal equipment according to the wastewater characteristics and treatment requirements of this project, adopting reverse osmosis technology combined with biological nitrogen removal technology.
After treatment, total nitrogen was reduced to below 10mg/L, reaching the Class B standard, and helping the customer achieve wastewater reuse.
Key data for this case in the original materials: 40mg/L before treatment, below 10mg/L after treatment.
11. Hospital Wastewater Total Nitrogen Treatment Case
The total nitrogen of the wastewater treatment system of a certain hospital reached 30mg/L, higher than the national emission standard of 20mg/L.
Aiming at project demands, ECOLINK installed professional nitrogen removal equipment and adopted reverse osmosis technology and biological nitrogen removal technology for treatment.
Ultimately, total nitrogen was reduced to below 15mg/L, reaching the Class A standard.
This case shows that for different types of wastewater, the causes and treatment methods for excessive wastewater total nitrogen need to be analyzed in combination with pollutant sources and specific water quality, and the exact same process cannot be blindly applied.
Original case data shows that hospital wastewater total nitrogen decreased from 30mg/L to below 15mg/L.
12. How to Choose a Suitable Total Nitrogen Treatment Scheme?
If an enterprise finds that effluent total nitrogen suddenly rises, it is recommended not to blindly add chemical agents or replace equipment immediately, but rather proceed with judgment according to the following steps.
Step 1: Confirm Total Nitrogen Composition Test:
TN
NH₄⁺-N
NO₃⁻-N
NO₂⁻-N
COD
BOD
pH
Temperature
TDS Judge whether the problem mainly occurs in the nitrification stage or denitrification stage through these data.
Step 2: Inspect Biochemical System Operating Conditions Focus on reviewing:
DO
MLSS
SRT
Sludge load
Internal reflux
External reflux
Aeration volume
Anoxic zone operating status
Step 3: Judge Whether Carbon Sources Are Insufficient If nitrate is high while biodegradable organic matter is insufficient, it is necessary to further analyze C/N conditions and carbon source dosing strategies.
Step 4: Determine Whether Advanced Treatment Needs to Be Added If discharge requirements still cannot be met after biochemical system optimization, membrane treatment or other advanced treatment technologies can be further considered.
Step 5: Match Equipment Based on Actual Water Quality For projects requiring upgrading or retrofitting, total nitrogen removal equipment and process combinations should be comprehensively determined based on treatment volume, influent total nitrogen, target effluent, site conditions, and operating costs.
13. Why Choose ECOLINK TECHNOLOGY?
ECOLINK TECHNOLOGY focuses on water treatment chemicals, wastewater treatment equipment, and water treatment solutions, providing product matching, technical support, sample testing, equipment schemes, and one-stop water treatment services according to different project demands.
For wastewater treatment total nitrogen excess projects, we focus not only on the final test data, but also on the actual causes causing the excess.
From front-end water quality analysis, to biochemical system operating conditions, to advanced treatment equipment, a reasonable technology route can help customers avoid unnecessary equipment investment and operating costs.
Our services can cover:
Wastewater total nitrogen problem analysis
Biological nitrogen removal process matching
Nitrogen removal equipment selection
Reverse osmosis equipment
Wastewater treatment equipment
ETP / STP solutions
Water treatment chemicals
Technical data support
Sample testing and product matching
Project technical communication and after-sales support
If your system is encountering problems such as continuous total nitrogen excess, high nitrate, unstable ammonia nitrogen removal, or upgrade difficulties in existing biochemical systems, you can send influent and effluent water quality data, treatment volume, and current process flow to ECOLINK TECHNOLOGY.
We can further analyze where the problem lies based on actual data and assist in matching suitable wastewater treatment total nitrogen excess treatment schemes.
Conclusion: The Key to Stable Nitrogen Removal is Finding the Real Cause of the Excess
Total nitrogen excess does not necessarily mean that the entire wastewater treatment system has failed.
In many cases, problems may stem from insufficient carbon sources, unreasonable dissolved oxygen control, insufficient sludge age, temperature changes, insufficient nitrification capacity, or inadequate denitrification conditions.
Therefore, the key to solving the problem of excessive total nitrogen in wastewater treatment is not just adding a treatment unit, but finding the true limiting factors in the process of total nitrogen generation, transformation, and removal.
Through reasonable nitrification-denitrification control, combined with necessary advanced treatment technologies, the stability of the system can be further improved.
ECOLINK TECHNOLOGY can provide water treatment product matching, technical support, and equipment solutions according to customer actual project conditions, providing more reasonable total nitrogen control ideas for industrial and other wastewater treatment projects.
