Wastewater analysis results not only indicate whether the effluent quality meets standards but also reflect the operational efficiency of the entire treatment system. For many businesses, this is the basis for preparing periodic environmental reports and serves as an important data source for monitoring the operational status of wastewater treatment facilities.
However, in reality, many units only stop at checking whether the parameters "pass" or "fail" without fully exploiting the value of the analysis report. Each parameter reflects a different treatment stage, from the efficiency of organic matter decomposition, nitrogen removal capacity, and sedimentation processes to the operating conditions of the microbiological system. Correctly reading and evaluating the analysis results will help businesses detect abnormalities early, proactively adjust operational modes, and limit the risk of environmental incidents.
For many businesses, the analysis report is often used as a document to prove that the effluent meets environmental standards. However, the value of the analysis report lies not only in determining whether the parameters exceed allowable limits but also in showing the operational trends of the entire treatment system.
In many cases, the system still meets the standards, but the treatment efficiency has begun to decline. For example, if COD or Ammonia tends to increase gradually over each analysis period, even while remaining below the standard limit, it can be a sign of changes in the influent pollution load, poor performance of the microbiological system, or unstable operation of certain treatment units.
Therefore, businesses should not evaluate analysis results based on individual parameters alone. Monitoring the fluctuation trends of parameters over multiple analysis periods, combined with actual operational data, will help identify abnormal signs early before effluent quality is affected.
.jpg)
Analyzing wastewater before discharging into the environment
To correctly evaluate the current status of the wastewater treatment system, businesses should read the results report in a specific sequence rather than randomly checking individual parameters. This approach helps quickly identify parameters that need prioritized monitoring and avoids jumping to conclusions without sufficient data.
The first step is to determine the technical standards applicable to the business's waste source. Depending on the type of production, domestic wastewater, medical wastewater, or industrial wastewater will be subject to different standards and specific control limits for each parameter. Correctly cross-referencing the standards helps businesses know which parameters are being controlled and immediately identify the ones requiring prioritized evaluation.
A single analysis result only reflects the water quality at the time of sampling. Meanwhile, comparing the results of multiple consecutive analysis periods will reveal the fluctuation trend of each parameter. For example, if the effluent COD increases from 35 mg/L to 50 mg/L and then to 70 mg/L over three consecutive analysis periods, it may still meet the standard. However, this trend indicates that the organic treatment efficiency is decreasing and needs to be checked before the parameter exceeds the allowable threshold. Typically, businesses should monitor at least 3–5 consecutive analysis periods to accurately evaluate the operational trend of the system.
After cross-referencing with standards and comparing them with previous periods, businesses should evaluate parameters in groups rather than individually. They can be divided into groups such as:
Evaluating by group will help businesses quickly identify which treatment stage is operating inefficiently instead of focusing on treating single parameters.
.jpg)
Note the sequence when reading environmental analysis results
After comprehensively evaluating the results report, businesses need to focus on parameters that directly reflect the operational efficiency of the system. These are also the parameters regularly monitored during operation and are closely related to each other.
pH is the parameter that should be checked first because it directly affects the activity of the microbiological system and the efficiency of many physicochemical and biological treatment processes. For most biological treatment systems, the appropriate pH is usually between 6.5 and 8.5. When the pH falls outside this range, microorganisms can be inhibited, reducing the efficiency of organic matter decomposition and Ammonia treatment. In addition, pH fluctuations also affect coagulation, flocculation efficiency, and disinfection capacity in the final stage. Therefore, if the pH tends to change abnormally over multiple analysis periods, businesses should check the influent water source, pH adjustment chemicals, and the system's operational mode before addressing other parameters.
COD and BOD are two parameters that reflect the organic load in wastewater as well as the treatment efficiency of the biological system. During monitoring, businesses should not only pay attention to the value at a single point in time but also evaluate the fluctuation trend over multiple analysis periods. If both COD and BOD increase, the cause is usually related to the influent organic load or a decline in biological treatment efficiency. Conversely, if only COD increases while BOD changes little, the wastewater may contain more hard-to-degrade organic compounds. Simultaneous monitoring of COD and BOD will help evaluate the status of organic matter treatment more accurately and serve as a basis for appropriately adjusting the operational mode.
TSS reflects the amount of suspended solids remaining in the water after the treatment process and is an important parameter for evaluating the efficiency of the sedimentation stage. If the effluent TSS increases continuously, businesses should simultaneously check the operational efficiency of the settling tank, the system's sludge retention capacity, the sludge recirculation mode, and whether sludge is being washed out with the effluent flow. In many cases, increased TSS not only reduces the treated water quality but also leads to increased effluent COD due to a portion of organic matter still adhering to the sludge flocs.
Ammonia and Total Nitrogen reflect the nitrogen removal efficiency of the biological system. Simultaneous monitoring of these two parameters helps evaluate nitrification and denitrification capacities, as well as the stability of the specialized microbiological system. If Ammonia tends to increase while COD remains stable, the cause is usually related to the nitrification process or the operating conditions of the aerobic tank rather than the influent organic load. For nitrogen removal systems, businesses should combine additional evaluations of DO, pH, alkalinity, sludge age, and aeration mode to correctly identify the cause before adjusting the technology or adding chemicals.
In addition to common parameters such as pH, COD, BOD, TSS, and Ammonia, many analysis reports also include Total Phosphorus, oil and grease, Coliform, or heavy metals, depending on the type of wastewater and applicable standards. These parameters often reflect the specific characteristics of each production industry. Fully monitoring these specific parameters will help businesses comprehensively evaluate effluent quality and meet environmental management requirements according to current regulations.
.jpg)
Wastewater analysis sample
One of the common mistakes when reading analysis reports is evaluating each parameter individually. In reality, parameters are always interrelated and reflect the efficiency of each stage in the treatment system. Therefore, simultaneously analyzing multiple parameters will help businesses correctly identify the area facing problems instead of focusing only on treating a specific parameter. For convenience in monitoring, below are some common cases when evaluating wastewater analysis results.
| Sign | Possibility to check |
| COD and BOD both increase | Influent organic load increases or biological treatment efficiency decreases |
| COD increases, BOD changes little | Appearance of many hard-to-degrade organic compounds |
| COD and TSS both increase | Sedimentation efficiency decreases, sludge is washed out with the effluent |
| Ammonia increases, COD is stable | Nitrification process declines or aerobic conditions are unsuitable |
| Multiple parameters increase together | Unstable system operation or influent load changes |
*The table above is for initial reference only. To accurately determine the cause, businesses need to combine it with additional operational data and the actual status of the treatment system.
This is a fairly common situation for biological treatment systems with a nitrification stage. If the effluent COD remains stable but Ammonia gradually increases over multiple analysis periods, the cause usually does not lie in the organic load but is related to the conversion of Ammonia to Nitrate. In this case, businesses should prioritize checking the DO of the aerobic tank, pH, alkalinity, sludge age, and the activity of the nitrifying bacteria group before adjusting chemicals or changing the treatment technology. In actual operation, immediately adding chemicals or increasing the amount of microorganisms when Ammonia increases is often ineffective if the cause stems from the system's operating conditions.
When COD and TSS both increase in one or more consecutive analysis periods, this is often a sign that sedimentation and biological treatment efficiencies are declining together. The cause may stem from sludge being washed out with the effluent, ineffective settling tank operation, inappropriate sludge recirculation modes, or a sudden increase in the influent pollution load. In this case, businesses should not just focus on reducing COD with chemicals but need to simultaneously check the system's sludge retention capacity, settling velocity, recirculation flow rate, and the operational status of the settling tank.
If COD, TSS, Ammonia, or Total Nitrogen all tend to increase over multiple analysis periods, businesses should evaluate the entire system comprehensively rather than treating individual parameters. This is usually a sign that operating conditions have changed compared to the design phase, such as increased wastewater flow, fluctuating pollution loads, microbiological system decline, or some equipment no longer achieving its initial efficiency. During the inspection, analysis results should be combined with operational data such as wastewater flow, DO, pH, recirculated sludge volume, MLSS, aeration mode, and the operational status of treatment units. Simultaneously evaluating these factors will help correctly identify the cause and limit unnecessary adjustments.
Wastewater analysis results only reflect the sample quality at the exact time of sampling. Therefore, a single abnormal result is not enough to conclude that the system is experiencing an incident or that treatment efficiency has declined. In reality, businesses should monitor at least 3 to 5 consecutive analysis periods combined with operation logs, wastewater flow, monitoring data (if any), and equipment operational status to evaluate the system's fluctuation trend. Correctly identifying the cause from the beginning will help businesses choose the appropriate solution, avoid unnecessary technology adjustments or chemical additions, reduce operating costs, and maintain long-term treatment efficiency.
Wastewater analysis results are not only a basis for evaluating effluent water quality but also a tool to help businesses monitor the operational efficiency of the entire treatment system. By knowing how to analyze the fluctuation trends of parameters and the relationships between them, businesses can detect abnormal signs early, proactively adjust operational modes, and limit the risk of environmental incidents.
In cases where parameters continuously fluctuate or treatment efficiency declines for an extended period despite operational optimization, businesses should comprehensively evaluate the current system status before deciding to renovate or upgrade. You can refer to the article "When Does a Wastewater Treatment System Need to be Renovated or Upgraded?" for a further basis in evaluating and choosing the appropriate solution.
