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floc, asb, figure 1, Aerated Stabilization Basins, consumption, concentration, growth phase, amount of time, blue food, bod, bacterial cells, bacterial growth curve

Biological Growth Curve in Aerated Stabilization Basins

Bacteria are present throughout an aerated stabilization basin (ASB), though their form and concentration may differ in the different areas of the ASB. At the front end of the ASB, where the influent enters and there is the highest concentration of biochemical oxygen demand (BOD), bacterial concentrations are higher and bacteria are dispersed as they are busy consuming the BOD. At the back end of the system, where BOD is sparse, bacteria form floc and settle out. The bacterial growth curve, as seen in Figure 1, characterizes the different growth stages of bacteria in relation to the amount of food (BOD) available.

Bacterial growth curvebbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbFigure 1: The Bacterial Growth Curve

The growth rate of the bacteria in the ASB is directly proportional to the amount of BOD available. Figure 1 shows the growth rate of the bacteria over time. The blue curve represents the amount of BOD available for consumption. The red curve represents the amount of bacterial mass in the bulk water. There are four distinct phases of bacterial growth: lag phase, log phase, declining growth phase and endogenous respiration phase.

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Biological Treatment, floatable solids, dition, aeration basin, biological waste treatment, bod, hydraulic overload, detention time

Primary Clarifier Operation

Primary clarification is the physical treatment process of removing solids before biological treatment. It is the most cost effective way to remove these solids after basic screening. Process water enters the clarifier tank and floatable solids (scum) are removed from the surface by skimmers while settleable solids (sludge) are collected on the bottom by a rake and removed via a sludge removal system. Effluent destined for biological treatment leaves the clarifier over a weir. The expected range for percent removal in a primary clarifier is 90%-95% settleable solids, 40%-60% suspended solids, and 25%-50% total BOD5.

Clarifier efficiency is based on hydraulic detention time, temperature of the water, the design of the tank and the condition of the equipment. Poor clarifier performance can be due to a variety of factors such as (1) hydraulic overload which decreases hydraulic detention time; (2) hydraulic under-load which doesn’t allow the equipment to work efficiently; (3) sludge buildup which causes decreased tank volume; and (4) highly concentrated waste streams. Bypassing a clarifier, which means routing plant effluent directly to secondary treatment in an aeration basin, should be done only in emergencies when clarifier equipment must be repaired or the sludge removal system is not able to process the sludge volume it receives. This scenario introduces high solids and elevated BOD levels into the biological treatment system and is not advised.

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laboratory training, Laboratory Audits

Is your lab data right?

 Improving the operation of environmental laboratories in industrial facilities benefit not only the environmental staff but other departments, as well. Accurate and timely analyses from the lab helps support decisions throughout the facility. This ensures compliance and can save thousands of dollars in lost production, unnecessary investigation or troubleshooting effort and expenses.

 

What are the benefits of a lab audit?

  1. Verify the lab is producing quality data efficiently.
  2. Provides the peace of mind in being compliant by meeting the rigorous standards of NPDES permits.

What’s the lab audit process?

  1. Discussion of concerns with processes, data or analytical testing.
  2. Evaluation of each technician’s laboratory technique and competency with all tests.
  3. Hands-on training. Generating quality data begins with having a well-trained staff to ensure everyone working in the lab is performing the tests the same way, and the correct way. The show, practice, do methodology.
  4. Ensures all permitted testing is performed in accordance with the requirements of Standard Methods and EPA test methods utilizing Best Laboratory Practices.
  5. Review SOPs generated through environmental testing and the associated quality control data. This is typically done with all environmental staff to demonstrate how to best utilize data from process control and permitting standpoints.

How long does a lab audit take?

A typical lab audit will take approximately 2-3 days on-site. The amount of time a lab audit requires is based on the size of the laboratory, the number of technicians, and the complexity of the operations. It is important to ensure that each concern and question is reviewed and addressed.

Contact us the next time you suspect your lab data might be off—or if results just aren’t lining up with what you’re seeing in the field.

We can help you develop a comprehensive audit for your laboratory to ensure it is operating effectively, efficiently and in full compliance with current regulations and procedures.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Activated Sludge Systems, biochemical oxygen demand, chemical program, chemical oxygen demand, Advanced Analytical Lab, Inhibition

Is Your Chemical Program Impacting Your Wastewater Biology?

Assessing Chemical Impacts on Wastewater Microbiology

Wastewater managers and operators want confidence that their facility’s chemical program will not negatively impact their biological treatment system. Whether you are a chemical supplier or product end user, EBS can assess chemical additives for impacts on microbiological activity.

Utilizing respirometry, EBS can continuously measure oxygen uptake or gas production, and therefore BOD removal, from a biomass exposed to different controlled conditions. To complement these results, we can also use Flow Cytometry, which measures the proportion of live and dead cells in each sample using nucleic acid stains. This dual approach provides both a metabolic and cellular view of microbial health under chemical stress.

In the case study below, three different doses of biocide used in upstream processes were added into reactor bottles containing the facility’s activated sludge biomass and typical influent at three different concentrations, in addition to the treatment plant biomass and aeration basin influent.

Christina Dietzen
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TSS | VSS, Activated Sludge Systems, biochemical oxygen demand, Biological Treatment

The importance of Primary Clarification: 

The Importance of Primary Clarification: A Key to System Efficiency

Well-functioning primary clarifiers are essential for wastewater treatment efficiency. However, they are often overlooked when diagnosing the causes of declining effluent quality. Their primary function is to remove insoluble BOD (such as fiber) and inorganic solids (like lime and ash), thereby reducing the load on the biological treatment stage. 

From a cost-saving perspective, primary clarifiers remove more BOD and TSS for less operational expense than any other treatment process, as rejected fiber from the process can contribute up to 0.4 pounds of BOD per pound of TSS. 

The diagram shows the difference between what enters the primary clarifier versus what leaves.

Green bars represent the TSS and BOD concentrations coming into the Unsettled Primary Clarifier Feed from the mill. If operators bypass the clarifier, this feed will go directly into the ASB.

Purple bars in the diagram represent the TSS and BOD concentrations in a typical Settled Primary Clarifier Effluent. These concentrations typically enter the ASB when the primary clarifier is functioning correctly.

Understanding Phantom BOD

Phantom BOD represents the insoluble portion of BOD that will not show up in the 5- day BOD test. This fraction will settle out somewhere in the ASB and break down to soluble BOD, creating additional oxygen demand later on. The primary clarifier significantly reduces the phantom BOD load to the ASB in this example. As seen in this diagram, a primary clarifier serves not only to reduce TSS but also a significant portion of BOD. Since more solids enter the ASB when bypassing the clarifier, bacteria will need time to acclimate to the higher BOD loading. There will likely be carryover of BOD and TSS into the effluent. Also, since more phantom BOD will be added to the ASB, the consequences of clarifier bypass may be seen weeks later in the treated effluent. 

Our experienced wastewater consultants help you closely monitor trends in primary clarifier performance, providing early detection of issues before they escalate. We also help ensure the biological portion of your treatment system remains resilient, even during periods when primary clarifier performance fluctuates!

Christina Dietzen
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Types of Organic Compounds In Industrial Wastewater

Testing for different categories of compounds in wastewater—such as readily biodegradable, slowly biodegradable, recalcitrant, and toxic compounds is crucial for several reasons related to environmental protection, wastewater treatment efficiency, and public health. Knowing the composition of your wastewater is key to selecting the most effective treatment program for your facility. At EBS, our lab is equipped to test for the presence and concentrations of many of these compounds, which are well-known to wreak havoc on the efficiency of biological treatment processes.

Following this analysis, EBS can provide further treatability testing to help you and your team develop the most effective action plan!

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Activated Sludge Systems, Suspended Solids

Free vs Bound Chemical Analysis

The return of healthy biological solids is essential to the performance of activated sludge systems. Along with concentrated biomass, inhibitory and toxic chemicals that can cause WET testing failures or treatment deficiencies may be returned to the system by being bound to the solids.  

Determining if inhibitory chemicals exist free in the bulk water or bound to the suspended solids within the aeration basin is beneficial to the plant operator. If these chemicals are adhered to solids through bioaccumulation, it is advisable to remove more suspended solids through the sludge wasting process from secondary treatment, rather than recirculating them back to the aeration basin. This process of sludge wasting is effective because these chemicals have already been neutralized, allowing for their safe removal. Alternatively, too much bioaccumulation on bacterial cells can inhibit the effectiveness and efficiency of removing BOD and cause settling issues. If there is a loss of suspended solids containing inhibitory chemicals or if these chemicals are free in the bulk water, WET testing toxicity or permit failure could occur. 

Free bound chem analysis fig1

Figure 1

As shown in Figure 1, the relationship between bound and free chemicals can change throughout the treatment system. Typically, influent streams contain inhibitory chemicals that are primarily free in the bulk water. In the biological basins, the bacteria can bind these chemicals. During secondary treatment, the solids can be wasted to reduce the recycling of the harmful chemicals back into the treatment system.   

In the laboratory, a monthly or quarterly representative sample set can be used to determine these relationships to get a more precise idea of how chemicals are bioaccumulating in a system operating under normal conditions. In upset events, abnormalities can help plant operators take appropriate corrective action.   

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Consulting, Activated Sludge Systems, biological treatment systems, activated sludge, Data review, chemical oxygen demand

Five Key Areas To Improve Your Wastewater System

Wastewater management is a multifaceted endeavor. Below are five critical areas that can significantly enhance your system’s effectiveness.

 

1. Generating reliable laboratory data

While it’s true what they say, “you can’t control what you don’t measure,” at times, you may be controlling for things that aren’t there. Ensuring that your on-site laboratory is generating reliable data is the first step to better understanding your wastewater treatment plant (WWTP). Virtually everything we know about system performance comes from lab data. If that data is misleading (or worse, flat-out wrong), it can have you chasing phantom problems. EBS worked with a facility in the past where loading was thought to have recently increased by more than double. Capital expenses were approved, system design changes were put in place, but no measurable effect was produced. Eventually, through a laboratory assessment, it was determined that COD/BOD testing was being done incorrectly and thus was yielding greatly exaggerated numbers. Staff turnover lead to diminished experience, and testing reliability was the cost. Erroneous data was being used to make process changes that, in the end, proved unnecessary. Ensure your data is reliable first, then act.

 

2. Monitor the eight growth pressures

Once you have established that your analytical processes are reliable, you need to determine what to monitor. The eight growth pressures are an excellent place to start. The growth pressure is the factors that often determine the success or failure of a biological treatment system. Keeping these growth pressures in their respective target range is essential for maximizing treatment efficiency. Most, if not all, of these growth pressures can easily be monitored through routine lab testing or online measurements. In some cases, a surrogate test can be performed and correlations drawn, increasing efficiency and speeding up the decision making process. COD testing, for instance, is commonly used to predict BOD loading. Each facility’s COD:BOD correlation will be unique, so spending the time to understand this relationship is essential. Once a good correlation is established, swings in loading can be detected in 2 hours rather than having to wait five days.

3. Establish Key Performance Indicators (KPI)

 After making sure that you can produce reliable data and knowing what to test for, establishing Key Performance Indicators (KPI’s) is an ideal next step. KPI’s allow you to set “guardrails” for the most important parameters in your WWTP. KPI’s should be determined on a site-specific basis, but typically include things like influent loading, flow, COD removal across an aeration basin, nutrient residuals, dissolved oxygen levels in an aeration basin, or clarifier turbidity. Every treatment plant will have its own sense of what “normal” is, so generating an adequate amount of baseline data under normal operating conditions is the best course of action. From this baseline, high and low guardrails can be set. These guardrails can be used to instantly understand where operations stand. After establishing guardrails, putting solid corrective actions in place for each KPI will help you resolve issues more quickly. If influent COD rises above a certain level should water be diverted to a holding pond or pond levels raised? If pH falls below a certain level should the automatic caustic feed kick on? Having a plan in place for situations like this before they happen allows you to be proactive rather than reactive and prevent small upsets from becoming big problems. 

4. Well trained operators

 Established KPI’s are essential for engineers to analyze WWTP efficiency, but the operators are the front line of defense. They should not only be well trained in the technical aspects of operating the equipment, but also in what their KPI’s are telling them. If COD values rise above X, do the operators understand what levers they can pull? If nutrient levels fall below the given guardrail, what should the nutrient pump rate be increased to? Why does the DO need to remain above 2 mg/L, and what does it mean if it suddenly plummets? The operations staff must be just as informed as the engineers on what the growth pressures and KPI’s are telling them, and what options they have at their disposal to affect change. Our semi-annual wastewater seminars and routine workshops are a great place to start if you need to improve your operator traning.

5. Advanced Monitoring Program

At times, all systems have issues that can’t be easily solved using a traditional monitoring approach. Keeping tabs on the eight growth pressures will allow you to keep the system between the lines most of the time, but anomalous conditions do arise. Having a routine monitoring program at your disposal can be a useful safety net. This may consist of routine data analysis, microbiological testing, or on-site consulting. Perhaps settleability in a secondary clarifier has worsened despite no apparent change in loading. It could be due to filamentous bacteria, and chlorination may be the solution. However, it could be from the overproduction of polysaccharides, and chlorination would exacerbate the problem. Advanced microbiological testing performed on some regular frequency (monthly, quarterly, etc.) will allow you to have a good baseline of even the most complicated parameters, ensuring you are armed with the information required to make the right decision. Established guardrails will also need to be adjusted over time due to changes such as decreased retention time, an increase in production, or tighter permit limits. A systematic schedule for data review helps address challenges prompted by these changes, ensuring continuous awareness and adaptability. This proactive stance enables timely adjustments and maintains the system’s compliance and performance.

Christina Dietzen
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