Wastewater Systems

Downloadable Documents
Categorical IU Monitoring Report [PDF]
IU Monitoring Report [PDF]
Application And Instructions for Industrial Wastewater Discharge Permit [PDF]
Permitted Liquid Waste Transporters authorized to work within the City of McAllen [PDF]
How Sewer Surcharge is Calculated [PDF]
Reference Guide for Installation of Grease Traps [PDF]
MPU Policy for Pretreatment Device-Grease Trap Sizing [PDF]
Plumbers List [PDF]
Industrial Wastewater Survey Form [PDF]
Lets Get The Grease Out [PDF]
Pretreatment Devices [PDF]
Keeping Fats, Oils and Grease out of the Sewer System [PDF]
Protect Waterways
Septic Tank System Guide
Wastewater Systems Staff
Name Position Phone
Marco Pedraza Director of Wastewater Systems 681-1750
Javier Hinojosa Asst. Director of Wastewater Systems 681-1750
Christina Alfaro Administrative Supervisor 681-1750
Terri Vasquez Administrative Assistant 681-1755
Joe Gonzalez Wastewater Collection Manager 681-1755
Julio Oviedo Supervisor 681-1755
Reynaldo Palomo South Treatment Plant Manager 681-1750
Jose L. Moreno North Treatment Plant Manager 681-1781
Rafael Gomez Wastewater Pretreatment Supervisor 681-1760
Jose Cantu Pretreatment Technician 681-1760
Liliana E. Espinoza
Administrative Clerk 681-1760

Overview

Wastewater Systems consist of three (3) divisions within the City of McAllen, McAllen Public Utilities Department which are Wastewater Pretreatment, Wastewater Collections, and Wastewater Treatment.

Wastewater Pretreatment

McAllen Public Utility Board (MPUB) in conjunction with the City of McAllen has implemented an Industrial Wastewater/Pretreatment Program for regulating the discharge of industrial and commercial wastewaters to the sanitary sewer system.

The general pretreatment regulations assign responsibility to the city or local sewerage authority to regulate industrial or commercial customers. All local authorities operating POTW’s (Publicly Owned Treatment Works) with total flows in excess of 5 MGD and which receive industrial wastes from sources subject to the national pretreatment standards are required to implement a Pretreatment Program as mandated through the Environmental Protection Agency (EPA).

MPUB continuously surveys for Industrial Users (IUs), who are subject to discharge regulations and may require a permit. The survey is accomplished by reviewing these periodic lists:

  • MPUB New Water Meter Taps
  • List of Businesses from the McAllen Chamber of Commerce
  • List of New Building Permits

These lists are review to identify industries which may generate a wastewater stream that contains either pollutants with limitations or high strength conventional pollutants such as BOD & TSS. These lists are also reviewed for industries regulated by an EPA Categorical Standard. MPUB sends a survey questionnaire to each IU suspected of generating a regulated waste discharge. An example of this form is attached with this memo. Returned questionnaires are reviewed and verification of data may require a site visit to the facility to determine whether all processes were described and all discharges correctly reported. This verification process may require the collection of samples to further characterize the IU’s wastewater. The survey results are used to classify the industry in one or more of the following groups.

Commercial
Commercial establishments such as restaurants, car washes, and laundromats are not permitted, but are routinely sampled for the high strength wastewater program. In which pretreatment collects a sample and runs BOD (biochemical oxygen demand) and TSS (Total Suspended Solids) analysis on these samples.
Categorical
Categorical Industrial User (CIU) which are permitted to control the discharge of toxic pollutants and to enforce the national categorical standards.
Significant Industrial User
(SIU), means all industrial users subject to categorical pretreatment standards under 40 CFR and any other IU that:
  1. discharges an average of 25,000 gallons per day or more of process wastewater to the POTW (excluding sanitary, non-contact cooling and boiler blow down wastewater);
  2. contributes a process waste stream which makes up 5 percent or more of the average day weather hydraulic or organic capacity of the POTW treatment plant; or
  3. is designated as such by the City as on the basis that the IU has a reasonable potential for adversely affecting the POTW’s operation or for violating any pretreatment standard or requirement (in accordance with 40 CFR 403)

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Wastewater Collections

The City of McAllen Wastewater Collection Department consists of 20 employees whom are responsible for the care and maintenance of the wastewater collection system. The Wastewater Collection System consists of 51 Liftstations throughout the City of McAllen and City of Alton that distribute the sewage to the two wastewater treatment plants for treatment.

Wastes are generated from homes, stores, restaurants, hospitals, and other community sources, such as industries: factories, refineries, food processors or metal platters that also will contribute to the wastes generated.

These wastes go directly into the collection system at their source, and then go through the collection system to the treatment plant. In the treatment system the sewage is conditioned for safe discharge into public waterways.

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Wastewater Treatment

Permits and Standards

Wastewater treatment plants operate under permits, which have been established to control pollutant discharges. Permits are designed to regulate the manner, nature, volume and frequency for discharging from a particular source. These permits establish specific limits on standards for discharging according to the rules and regulations of the State of Texas, orders of the Texas Commission on Environmental Quality and according to the Federal (EPA) agency. These permits also insure that the limits and standards established are met through proper enforcement (i.e. annual plant inspections, bio-monitoring and compliance monitoring).

This department is comprised of two (2) facilities with in the City of McAllen and treats all of McAllen’s wastewater as well as the City of Alton thru an Interlocal agreement. These facilities are the South Wastewater Treatment Plant with a design capacity of 10 MGD, located on the South side of McAllen and the North Wastewater Treatment Plant with a design capacity of 6 MGD, which has recently completed a 2 MGD expansion, brings the design capacity to 8 MGD, located on the North side of McAllen. The North Wastewater Treatment Plant sells a portion of its reclaimed effluent to the Power Generation Plants for their cooling towers and the South Wastewater Treatment Plant provides reclaimed effluent to the McAllen Palm View Golf Course for irrigation.

Treatment Process

The McAllen Wastewater Treatment Plants are an extended aeration activated sludge process. Activated sludge is the sediment from sewage that has been agitated in the presence of oxygen. This sediment of “activated sludge” contains living organisms that feed on sewage and require oxygen to live.

In this treatment system, the raw wastewater passes thru an influent channel with a mechanical bar screen. The wastewater after mechanical screening then flows to the aerated grit chamber that removes gritty materials in the waste. After the grit chamber, the wastewater flows to the aeration tanks for biological stabilization.

The mechanical surface aerators in the aeration basin agitate the mixture of the wastewater and sludge, which is then stabilized and settled in the final clarifiers. A portion of the sludge from the final clarifiers is digested in the aerobic sludge digester and a portion of the sludge is returned to the aeration basins to provide the necessary microorganisms in the aeration basins.

The clarified wastewater effluent flows then to the chlorine contact chamber for disinfection with chlorine gas and before discharge to the Parshall flume; chlorine is removed with sulfur dioxide.

The digested sludge from the aerobic digester is stored in the sludge holding tanks (digesters) and then dewatered in sludge drying beds. Which is later harvested once dried and hauled off for beneficial land application.

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