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P O T W CHARACTERISTICS
Introduction
A publicly owned treatment works (POTW) is responsible for collecting and treating wastewater, consisting of a sewer system for conveyance and a treatment system for processing Understanding the components and limitations of POTWs can enhance the success of terminals in negotiating and implementing effluent discharge programs.
This section discusses the POTW conveyance system, treatment system processes, typical requirements of a
POTW’s operating permit, and operating limitations of
POTWs The information is the basis for the PUTW concerns described in Section 4.
Components of a POTW System
This section discusses the sewer and treatment systems
These systems are primarily intended for the management of residential wastewater, specifically domestic sewage However, they may also be designed to accommodate contributions from industrial and commercial sources, depending on the community's needs.
Wastewater is transported through a system of sewers and pump stations to a treatment facility, primarily relying on gravity, which often leaves the pipes only partially filled This creates an air space above the wastewater, where flammable gases like hydrogen sulfide can accumulate, posing a significant explosion risk.
Pump stations are essential for transferring wastewater over long distances or elevating it to enable gravity flow The wetwells of pump stations store wastewater until the water level triggers the pumps During this accumulation, gases can volatilize and accumulate in the air space above the wastewater.
Pump stations contain moving metal components that may generate sparks Although these parts are typically housed in a separate dry-well compartment, hazardous gases like hydrogen sulfide can infiltrate this space, creating a risk of explosion.
Sewer workers need to access the conveyance system via manholes for routine maintenance and emergency work
Manholes and pump stations necessitate confined space entry due to the presence of gases in municipal wastewater systems that handle domestic sewage Toxic gases like hydrogen sulfide pose significant risks, while nontoxic gases are also a concern as they can displace air within the sewer system Additionally, P O W operators must be vigilant about potential exposure to volatile and possibly toxic contaminants released by industrial users.
1.2.2 TYPICAL WASTEWATER TREATMENT SYSTEM COMPONENTS
Wastewater treatment plants utilize a combination of solids settling, biological degradation, and disinfection to purify wastewater The complexity and configuration of these plants can vary significantly between Publicly Owned Treatment Works (POTW) and other facilities While most plants focus on liquid and sludge treatment, some have begun to incorporate air and odor treatment as well Key processes involved in wastewater treatment are outlined, with specific concerns related to POTWs highlighted A typical arrangement of these processes is illustrated in Figure 1.
At certain wastewater treatment plants, influent pumping stations elevate wastewater to enable gravity flow through the facility However, these pumps have hydraulic limitations, and overloading can lead to sewer backups and potential wastewater overflows Additionally, since the influent pumping chamber is the lowest point in the conveyance system, it can accumulate vapors that are heavier than air, raising concerns about explosion hazards for plant operators.
Treatment processes work better with stable inputs of flow and waste Wastewater flows to P O W s tend to follow a
The diurnal curve illustrates predictable sewer flow patterns, with peaks typically occurring after morning and afternoon commutes, while low flows are observed during inactive hours, such as after midnight This variation is more significant in smaller publicly owned treatment works (POTWs), whereas larger POTWs, serving bigger communities, experience diverse water use patterns that mitigate these fluctuations To manage high variations in flow or waste strength, treatment plants may implement equalization basins to stabilize the impact on the overall treatment system.
The headworks, located early in the process train, screen out large debris that can clog or otherwise damage equipment downstream Equipment may include a bar screen, which acts
Provided by IHS under license with API
Low point in Trash weening plant where Comminutor hydrocarbon Grinding vapors could Grit collection ammulate Often in endosed building
Gravity settling of Activated sludge, Usually chlorination wastewater s o l i trickling filters, or to kill pathogens
Sludge is usually aemted lagoons collected and are common managed with Biological solids biological solids are usually collected, digested, dewatered, and land application disposed by
Figure 1-Typical Municipal Wastewater Treatment Plant Process with Issues Related to Terminals Noted)
12:oo AM 6:ûû AM 12:OO PM 6:oO PM
Figure 2-Typical Treatment Plant Inflow Curves (Weekday, Residential, Conditions)
Provided by IHS under license with API
STD.API/PETRO PUBL 1bL2-ENGL 1 7 7 b = 0 7 3 2 2 7 0 0 5 b 2 8 3 7 1 7 b
The guidance document outlines the discharge of petroleum distribution terminal effluents to publicly owned treatment works, emphasizing the importance of headwork equipment such as hash racks and comminutors, which function similarly to garbage disposals by grinding up debris Typically, this equipment is housed in an enclosed building, raising concerns about potential explosions due to the mechanical moving parts and the confined space.
The grit chamber, located after the headworks, effectively removes inorganic solids like stones from the conveyance system This grit removal process is essential for safeguarding downstream equipment from abrasive materials.
Gravity settling of wastewater solids provides primary treatment by removing readily settleable organic material
Liquid overflows to the next pmcess, the biological treatment unit The sludge coiiected from the clarifier bottom is pumped to sludge processing units i 22.6 Biological Treetment
Secondary treatment effectively eliminates most organic contaminants by utilizing living microorganisms, specifically bacteria, that feed on organic matter In Publicly Owned Treatment Works (POTWs), these microorganisms primarily consume organic waste from domestic sources, allowing them to adapt to typical household sewage However, POTWs face challenges when nondomestic wastewater introduces unusual contaminants that can harm or inhibit microbial growth, or that are beyond the microorganisms' capacity to degrade Protecting these microorganisms is crucial, as sending untreated contaminants through the treatment plant poses significant risks Further details on these issues are explored in section 2.
Several process configurations are commonly used in
POTWs utilize various configurations such as activated sludge, trickling filters, rotating biological contactors, and lagoons to effectively treat wastewater These systems facilitate the interaction between microorganisms and wastewater, ensure adequate oxygen supply for microbial activity, and regulate the microorganism population to maintain optimal treatment efficiency.
Activated sludge, one of the most common biological treat- ment processes, uses continuous-flow aeration basins for mixing the wastewater, microorganisms, and air together
Microorganism communities, known as flocs, thrive in basins by consuming wastewater contaminants, ultimately growing to macroscopic sizes and becoming the main component of the solids present These mixed solids then flow into a clarifier, where the microorganism solids are separated.
In wastewater treatment, settled sludge is removed, allowing the clarified liquid to flow to subsequent treatment stages Some of the settled microorganisms are recycled back to the aeration basin to enhance the treatment of incoming wastewater, while others are disposed of Effective process control is essential to sustain optimal aeration basin conditions, ensuring the ideal growth environment for microorganisms.
Trickling filters utilize stationary media, such as plastic or stones, to support the growth of microorganisms Wastewater is distributed over this media, allowing microorganisms to form a slime layer that degrades contaminants as the water flows past The treated wastewater is then directed to a clarifier, where solids from the slime layer are settled out.
Performance Requirements of P 0 " s
POTws, like tennuials, are part of the regulated commu- nity Treatment plant discharges must comply with National
The Pollutant Discharge Elimination System (NPDES) permit imposes specific conditions that must be adhered to, as violations can result in regulatory intervention, fines, and enforcement actions Additionally, breaches of the NPDES permit may lead to environmental lawsuits initiated by third parties These permits encompass various requirements, which are primarily divided into flow limits and concentration limits.
NPDES permits establish maximum concentration limits for specific contaminants based on either technology or water quality Technology-based limits reflect the capabilities of treatment processes, such as biological treatment, which can remove around 85 percent of influent organic contaminants In contrast, water quality-based limits are designed to protect the health and designated uses of receiving waters, ensuring that discharged contaminants do not create toxic conditions for aquatic life.
The POTw's discharge is rouiinely analyzed for regulated contaminants Any exceedences associated with industxial
discharges indicate that the POTw may not be effectively treating the indusirial contaminant, meaning that pass- through is creating permit violations for the POTW
An NPDES permit specifies the maximum flow rate that a
PUIW discharges may lead to wastewater flow rates that necessitate investigations into treatment plant expansions by the POTW Consequently, POIWs closely monitor residential and industrial connections, stormwater discharges, and groundwater infiltration into sewer systems POTWs are increasingly reluctant to accept stormwater, viewing it as a nonwastewater stream that could exacerbate existing issues.
Sustained successful performance of the wastewater treat- ment plant requires control of the two primary operating con- sirainợs: hydraulic (flow) loading and mass (contaminant) loading
Flow limitations can affect both the sewer system and the treatment plant, as the pumps and process units are engineered for specific hydraulic capacities When pumps or sewers experience hydraulic overload, it can result in overflows Excessive flow rates hinder adequate hydraulic detention during disinfection, which compromises pathogen destruction As detailed in section 3.4, the terminal effluent volumes are minimal and are expected to have a negligible impact.
POTW inủuent flow rate It is unlikely that terminai efủuents have a high enough volume to create hydraulic problems at a m
Treatment plant process units are engineered to handle specific influent loading of contaminants measured in pounds per day Exceeding these loadings can disrupt the treatment processes The terminal effluent mass loadings are minimal, as illustrated in the mass balance example in Appendix A, and are expected to have a negligible impact on the overall system.
POTW infiuent composition It is unlikely that terminai efủuents have a high enough loading to upset a POTW pro- cess
The latest edition or revision of the referenced publications will be included in this document as specified When specific sections, such as numbered paragraphs or tables, from other documents are mentioned, the version in effect at the time of this publication will be applicable.
Provided by IHS under license with API
GUIDANCE DOCUMENT FOR THE DISCHARGE OF PETROLEUM DISTRIBUTION TERMINAL EFFLUENTS TO PUBLICLY OWNED TREATMENT WORKS 5
Pub1 4602 Minimization, Handling, Treatment, and 440/1-82/303 Faze of Prior@ Pollumts in Publicly
40 Coak of Fedem1 Reguktions, F4Kts 122,303, and 403
Guidance Manual on the Lkvebpmmt und Impkmentation of Local Discharge Lunitations Under the Pretmüment Program Indusrial User Permining Guidance Manual
Disposal ofthe P e t r o k m Products Ter- m'nal Wawwater
Treatmerir of P e t r o k m Marketing Eflue# in a Pub- licly Owned Treatment Facility
SECTION 2-PR ETR €ATM ENT RE W I R EM ENTS
POTWs must effectively manage and treat complex wastewaters that include both domestic and industrial discharges Since most system components are designed for domestic waste, it is essential for POTWs to implement a pre-treatment program to control industrial discharges This program not only authorizes but also mandates the necessary measures for effective wastewater management.
This section outlines the importance of regulating the quality and quantity of industrial discharges, focusing on pretreatment programs, classifications of industrial users, and typical pretreatment requirements that impact petroleum terminals Additionally, it discusses the establishment of local limits to ensure compliance and protect the environment.
The PAS National Pretreatment Program was created to manage the entry of contaminants from non-domestic sources into Publicly Owned Treatment Works (POTWs) This program is designed for local implementation by the POTW, following the guidelines established by federal EPA regulations (40 CFR Part).
Many states have been authorized to implement the F " s ' programs, ensuring that regulatory oversight is maintained locally to address community interests effectively Figure 3 illustrates the states that have EFA-approved pretreatment programs, while those without such approval must comply with established regulations.
The MRMAI procedure requires the Publicly Owned Treatment Works (POTW) to develop a jxetreatment program, detailing its elements as outlined in this section, and submit it for approval to the state or the EPA In exceptional circumstances, the state or EPA may assume responsibility for preparing the program.
POTW The terminal should identify the agency having authority for implementing the program
The pretreatment program aims to achieve several key objectives, primarily focusing on preventing contaminants that could disrupt the normal operation of the sewer system from entering it.
'Brown and Caldwell, P.O.BOX 8045, Walnut Creek, California 94596
The EPA-approved state pretreatment program aims to prevent plant upsets caused by contaminants that can pass through treatment facilities, leading to environmental harm Pass-through occurs when a treatment plant fails to effectively remove a contaminant, resulting in effluent concentrations that exceed permit limits or violate water quality standards Additionally, the program prioritizes the safety and health of sewer workers by prohibiting the discharge of flammable or toxic materials, which can create hazardous working conditions It also seeks to avoid restrictions on sludge disposal options due to contaminants in the sludge and to minimize the introduction of clean water into the sewer system, thereby preserving its hydraulic capacity Finally, the program ensures that oily or viscous discharges do not damage the publicly owned treatment works (POTW) by clogging pipes or coating equipment.
2Enviromental Protecrion Agency ù ủ e Code of Fedemi Regulations (CFR) is available from the U.S Government F'rinting office, Washington D.C
Provided by IHS under license with API
780 M g To p h i b i t the discharge of corrosive and/or reactive materials to the p(Trw
These major objectives are achieved through local ordi- n a n ~ e ~ , i n d u s a pretreatment pro gram^, and industrial dis- charge limits
The pretreatment program aims to establish and enforce a fee structure that adheres to federal and state regulations, implement a compliance enforcement plan for the sewer ordinance, and ensure that information regarding industrial discharges is accessible to the public.
As part of the pretreatment program, a POTW identifies the most significant industrial dischargers and focuses discharge controls on them These dischargers are called signijkm industrial users (SIUS)
It is important for a terminal to become familiar with its
POTWs should ensure that terminal effluents do not significantly impact contaminant or hydraulic loading To prevent an unrealistic designation as a Significant Industrial User (SIU), terminals must engage in effective communication with the POTW and implement appropriate wastewater management practices.
Referenced Publications
The latest edition or revision of the referenced publications will be included in this document as specified When specific sections, such as numbered paragraphs or tables, from other documents are mentioned, the version in effect at the time of this publication will be applicable.
Provided by IHS under license with API
GUIDANCE DOCUMENT FOR THE DISCHARGE OF PETROLEUM DISTRIBUTION TERMINAL EFFLUENTS TO PUBLICLY OWNED TREATMENT WORKS 5
Pub1 4602 Minimization, Handling, Treatment, and 440/1-82/303 Faze of Prior@ Pollumts in Publicly
40 Coak of Fedem1 Reguktions, F4Kts 122,303, and 403
Guidance Manual on the Lkvebpmmt und Impkmentation of Local Discharge Lunitations Under the Pretmüment Program Indusrial User Permining Guidance Manual
Disposal ofthe P e t r o k m Products Ter- m'nal Wawwater
Treatmerir of P e t r o k m Marketing Eflue# in a Pub- licly Owned Treatment Facility
SECTION 2-PR ETR €ATM ENT RE W I R EM ENTS
POTWs must effectively manage and treat complex wastewaters that include both domestic and industrial discharges Since most system components are designed for domestic wastewater, it is essential for POTWs to implement control measures for industrial discharges This control is facilitated through a pre-treatment program that not only authorizes but also mandates the proper handling of these industrial inputs.
This section outlines the importance of regulating the quality and quantity of industrial discharges, focusing on pretreatment programs, classifications of industrial users, and typical pretreatment requirements that impact petroleum terminals Additionally, it discusses the establishment of local limits to ensure compliance and protect the environment.
The PAS National Pretreatment Program was created to manage the entry of contaminants from non-domestic sources into Publicly Owned Treatment Works (POTWs) This program is designed for local implementation by the POTW, following the guidelines established by federal EPA regulations (40 CFR Part).
Many states are authorized to manage the F " s ' programs, ensuring that regulatory oversight is maintained locally to address community interests effectively Figure 3 highlights the states with EFA-approved pretreatment programs, while those without such approval must comply with established regulations.
The MRMAI procedure requires the Publicly Owned Treatment Works (POTW) to develop a jxetreatment program, detailing its elements as outlined in this section, and submit it for approval to the state or the EPA In exceptional circumstances, the state or EPA may assume responsibility for preparing the program.
POTW The terminal should identify the agency having authority for implementing the program
The pretreatment program aims to achieve several key objectives, primarily focusing on preventing contaminants that could disrupt the normal operation of the sewer system from entering it.
'Brown and Caldwell, P.O.BOX 8045, Walnut Creek, California 94596
The EPA-Approved State Pretreatment Program aims to prevent plant upsets caused by contaminants that can pass through treatment facilities, leading to environmental harm Pass-through occurs when a treatment plant fails to effectively remove a contaminant, resulting in effluent concentrations that exceed permit limits or violate water quality standards Additionally, the program ensures the safety and health of sewer workers by prohibiting the discharge of flammable or toxic materials, which can create hazardous working conditions It also addresses the need to avoid restrictions on sludge disposal options due to high contaminant concentrations Furthermore, the program seeks to minimize the introduction of clean water into the sewer system, thereby preserving its hydraulic capacity for wastewater Lastly, it protects the Publicly Owned Treatment Works (POTW) from damage caused by oily or viscous discharges that can clog pipes and coat equipment.
2Enviromental Protecrion Agency ù ủ e Code of Fedemi Regulations (CFR) is available from the U.S Government F'rinting office, Washington D.C
Provided by IHS under license with API
780 M g To p h i b i t the discharge of corrosive and/or reactive materials to the p(Trw
These major objectives are achieved through local ordi- n a n ~ e ~ , i n d u s a pretreatment pro gram^, and industrial dis- charge limits
The pretreatment program aims to establish and enforce a fee structure that adheres to federal and state regulations, implement a compliance enforcement plan for the sewer ordinance, and ensure that information regarding industrial discharges is accessible to the public.
As part of the pretreatment program, a POTW identifies the most significant industrial dischargers and focuses discharge controls on them These dischargers are called signijkm industrial users (SIUS)
It is important for a terminal to become familiar with its
POTWs should ensure that terminal effluents do not significantly impact contaminant or hydraulic loading To prevent an unrealistic designation as a Significant Industrial User (SIU), terminals must engage in effective communication with the POTW and implement appropriate wastewater management practices.
Federal regulations under 40 CFR Part 303 outline the criteria for wastewater discharge These criteria include: a) Categorical industries defined in 40 CFR Part 403, which encompass over 40 large contaminant dischargers, including petroleum refineries, while terminals are not classified as such; b) Industries with an average discharge of 25,000 gallons per day of process wastewater, excluding sanitary and non-contact cooling water; c) Industries contributing a flow rate that exceeds 5 percent of the average dry weather hydraulic capacity of the treatment facility; and d) Industries that produce a waste load surpassing 5 percent of the organic capacity of the Publicly Owned Treatment Works (POTW), where organic capacity refers to the design influent biochemical oxygen demand.
Industries with the potential to cause permit violations for the Publicly Owned Treatment Works (POTW) must be closely monitored This includes any industry that could adversely affect the operation of the POTW or violate pretreatment standards and requirements.
Terminals are unlikely to receive an SIU designation based on the initial five criteria related to flow or contaminant loading However, the final two criteria, which address potential issues, could lead to a terminal being classified as an SIU This guidance document aims to equip both terminals and PoTWs with the necessary knowledge and tools to prevent this inappropriate designation.
In many states, industries or Publicly Owned Treatment Works (POTWs) can petition to have a Significant Industrial User (SIU) designation revoked To achieve this, the industry must demonstrate that their discharge poses no reasonable potential to affect the treatment facility or breach established treatment standards.
2.32 TYPICAL REQUIREMENTS FOR NONSIGNIFICANT INDUSTRIAL USERS
Pretreatment programs establish discharge requirements common to both nonSIus and SlUs The common require- ments are presented in this section, and the SIU-specific requirements are presented in 2.3.3
Industrial discharge regulations typically focus on local limits, spill prevention, access for POTW inspections, waste disposal, and associated fees Generally, non-SIUs are not mandated to monitor, sample, or report their discharges, although they may need to initially characterize their waste and document flow.
AU industrial dischargers must meet local discharge limits
The local limitsdefine maximum amounts of contaminants in industrial discharges (see 2.4)
Spill prevention and control procedures and safeguards are required of ail industrial dischargers Terminals implement such procedures due to other reguiations