**Published Article-Limits Page Explained (WWT Discharge Permit)**

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**Ask Dan, the Wastewater Wizard**

*How to troubleshoot? “Discharge Permit Compliance working within the Limit’s Page”*

Industries should consider: This submission addressing requirement of-Discharge Permit Compliance working within the Limit’s Page.

__Project Details:__

Define and explain the concept:

Explore example:

Examine result:

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__Define and explain the concept:__

This project began with overall examination of Documentation of the Discharge Permit.

This project; Permit compliance working with the limits page of the discharge permit starts by analyzing the entire permit and understanding the Limits on the discharge permit.

As you analyze the permit, recognize the issuer of the permit will either be the United States Environmental Protection Agency (EPA), local state Environmental Department or the receiving Sewer Authority.

If the discharge permit is issued by the EPA or the local state environmental department the discharge is regulated under the National Pollutant Discharge Elimination System (NPDES).

If the discharge is issued by the local Sewer Authority the Sewer Authority receives the discharge and treats the discharge to release into environmental surface waters.

All permit limits are pre-approved by the local state environmental department.

In analyzing the discharge permit pay attention to the permit issuer, discharger, issue date and expiration date.

Identify certain important sections of permit including Effluent characteristics discharge limitations and monitoring requirements, responsibilities for reporting monitoring results and special requirements.

So the first thing that I would do is to locate the effluent limits and monitoring requirements page I call it the limits page.

Most permits include self-monitoring sampling privileges.

Also if your industry is categorized under the 40 Congressional Federal Register (CFR),it will be noted along with the required parameters to be analyzed.

The discharge permit limits, are detailed with four items as follows; parameter, discharge limitations, monitoring frequency and sample type.

Working with The Effluent Limitations & Monitoring Requirements page for our discharge permit, I usually look at the most frequent timeframe for monitoring.

It could be as frequent as three consecutive days a month to as infrequent as semi-annual. Most often, monitoring requirements for each parameter is monthly.

The discharging industry needs to comply with all monitoring frequencies.

Collecting the appropriate sample type is also required. The two types of samples collected are either grab or 24 hour composite.

Common parameters for analysis include Biochemical Oxygen Demand (BOD), Total Suspended Solids (TSS) and Oil & Grease (O & G).

Satisfying Discharge Permit Limits is critical to achieving Permit Compliance.

Discharge Limits are Monthly Average, Daily Maximum or both. Also the numeric limits are expressed in Concentrations (Mg/L) or Mass Pounds (Lbs. /Day) or both.

Examples and explanation of an Industry Discharge Permit-Limit’s Page is below:

Industry must also comply with reporting requirements which may be as quick as reporting during the month of sampling to as late as twenty days into the subsequent month.

Now that we have an illustration of the Permit Limits Page above, let’s look below at examples and interpretations. of

__Explore example:__

Now that we have a discharge permit illustration above, seven examples of parameters with discharge limits.

The **first parameter** on the top of the list is BOD

**. The discharge limit is Daily Maximum expressed in Milligrams per Liter (Mg/L) and Pounds per Day (Lbs. /Day). The monthly average is M & R (Monitor and Report). The monitoring frequency is monthly and the sample type is 24 hours.**

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The important interpretation is the limit is expressed as daily maximum which means permit compliance must be satisfied in a single sample event.

The **second parameter** is Total Suspended Solids (TSS). The limits are expressed as Monitor & Report (M & R) which means samples must be collected, analyzed and reported. No limits are required for compliance.

The **third parameter** is Oil & Grease (O & G) which has the same numeric limit as Milligrams per Liter for Daily Maximum and Monthly Average.

The important interpretation; when the numeric limit is the same for daily maximum and monthly average, permit compliance must be satisfied in a single sample event.

The **fourth parameter** is Ammonia Nitrogen which has different numeric limits as Milligrams per Liter and Lbs. /Daily for both Daily Maximum and Monthly Average.

Complying with all four numeric limits varies according to scenarios as follows:

__Scenario #1:__

During a 24 hour sample event, discharge flow was 3.125 MGD and lab result was 25 Mg/L. The calculated; Lbs. / Day is ** 652** = 3.125 X 25 X 8.34

The important interpretation; Scenario #1 is compliant with 25 Mg/L below both Monthly Average of 30 and Daily Maximum of 40 and 652 Lbs. /Day is below both Monthly Average of 750 and Daily Maximum of 1,125.

__Scenario #2:__

During the first 24 hour sample event, discharge flow was 3.125 MGD and lab result was 35 Mg/L. The calculated; Lbs. / Day is ** 912** = 3.125 X 35 X 8.34

The important interpretation; Scenario #2 is compliant/below Daily Maximum with 35 Mg/L below 40 and 912 Lbs. / Day below 1,125. However in violation/above Monthly Average with 35 Mg/L above 30 and 912 Lbs. / Day above 750.

This circumstance of complying with Daily Maximum and violating Monthly Average allows the discharger to collect another sample within monitoring frequency to be used to lower the Monthly Average.

The additional sample could be used to achieve compliant Monthly Average as follows:

During the additional/second 24 hour sample event, discharge flow was 3.125 MGD and lab result was 22 Mg/L. The calculated; Lbs. / Day is ** 573** = 3.125 X 22 X 8.34

The compliant average Mg/L is ** 29** = (35 + 22) ÷ 2

The compliant average Lbs. / Day is ** 743** = = (912 + 573) ÷ 2

The important interpretation; Scenario #2 is compliant with 29 Mg/L below both Monthly Average of 30 and Daily Maximum of 40 and 743 Lbs. / Day below both Monthly Average of 750 and Daily Maximum of 1,125.

Compliance also requires every sample result below Daily Maximum.

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__Scenario #3:__

During a 24 hour sample event, discharge flow was 3.125 MGD and lab result was 70 Mg/L. The calculated; Lbs. / Day is ** 1,824** = 3.125 X 70 X 8.34

The important interpretation; Scenario #3 is in violation with 70 Mg/L above both Monthly Average of 30 and Daily Maximum of 40 and 1,824 Lbs. /Day is above both Monthly Average of 750 and Daily Maximum of 1,125.

An additional sample can be used in this scenario #3 to achieve compliant Monthly Average. However, an additional sample in this scenario #3 cannot be used to avoid violation with Daily Maximum.

The **fifth parameter** is the first entry on flow. The discharge limit is Daily Maximum expressed in Million Gallons per Day (MGD) and Gallons per Minute (GPM). The Monitoring Frequency is 3 Consecutive Days.

The important interpretation; is that flow as GPM must always be satisfied and flow as MGD must always be satisfied.

The **sixth parameter** is the second entry on flow. The discharge limit is Monthly Average expressed in Million Gallons per Day (MGD).

The important interpretation; when the numeric daily flow limit is monthly average, the result is the effluent discharge for the month divided the number of days in the month.

The **seventh parameter** is pH which has a range between 6.0 and 11.0.

__Examine result:__

Discharge Permit Compliance requires paying close attention to detail as explained with illustration above.

Documenting Discharge Permit Compliance is a component of Record Retention Requirements included in a recent article.