The term pretreatment means the reduction of the amount of pollutants, the elimination of pollutants, or the alteration of the nature of pollutant properties in wastewater prior to, or in lieu of, discharging or otherwise introducing such pollutants into a publicly owned treatment works (POTW). The requirement to develop and operate an industrial pretreatment program was promulgated by the EPA and became effective on March 30, 1981.

The General Pretreatment Regulations are set forth in the Code of Federal Regulations, 40 CFR 403. Under the regulations, any POTW with a design flow greater than 5 million gallons per day (mgd) must establish a pretreatment program as a condition of its National Pollutant Discharge Elimination System (NPDES) permit. The District has developed a pretreatment program and obtained approval from the State Division of Water Quality to administer its pretreatment program with authority to permit, monitor, and enforce the requirements of the program. The District has legal authority to impose fine s on any user for non-compliance within the provisions of its wastewater control ordinance and pretreatment program. The District monitors the discharges of all significant industrial users (SIU’s) within its boundaries. SIU is a term assigned by the EPA to industries meeting specified criteria based on their potential to impact, interfere, or upset the ability of a treatment plant to treat the wastewater stream and meet its discharge standards. The total industrial flow in the District has been estimated to make up 10% of the total plant flow.

Routine tasks associated with the District’s pretreatment program include screening new businesses for the need to permit and monitor; inspecting industrial users’ facilities; inspecting and assessing the proper use and maintenance of grease traps at restaurants and other oil and grease generating businesses; performing sampling of monitored industrial discharges; evaluating lab reports to determine individual industrial user compliance; sending proper notice of violation occurrences; assessing fines when appropriate; consulting with industries concerning pretreatment requirements; compiling and filing records required for the State and EPA, billing of industrial users; calculating and implementing technically based local limits; and staying current on applicable State and Federal pretreatment regulations.

Annually the State conducts an inspection and audit of the District’s pretreatment program. During this inspection they verify compliance with applicable regulations and determine whether the District’s pretreatment program is being properly administered.

All SIU’s are required by the District to be permitted. In an industry’s permit, discharge limitations are specified. These limitations can either be prescribed by federal categorical standards or locally developed and imposed standards. All SIU’s are monitored to determine compliance with their permitted limitations. Each industry is given the option of performing their own monitoring or having the District perform the monitoring. If an industry elects to perform its own monitoring, the District must still perform at least one quarter of the monitoring to verify accuracy. The monitoring performed consists of taking samples using battery operated automatic samplers. These samplers are programmed to automatically take samples over a 24-hour period. It is important to preserve and maintain the most representative and accurate sample possible. This includes using proper techniques as well as verifying security against tampering. A specific and special sampling manhole is provided by each industry for pretreatment monitoring purposes.

After samples have been taken, they are delivered to either the District’s laboratory or a third party certified laboratory of the industry’s choosing. The laboratory runs analyses on the samples to determine the concentrations of specified pollutants. An analysis report is provided by the laboratory to the District’s Pretreatment Coordinator. The coordinator then reviews the analysis reports for compliance and enters all data into a special pretreatment computer program. The computer program helps determine compliance and maintains all pertinent records and data on all monitored industries.

If, upon evaluating the reported analysis data, a violation of discharge limitations or other requirements is discovered, the pretreatment coordinator notifies the offending industry by phone and/or formal written notification. If the industry does not restore compliance within a given period, enforcement response is escalated. The District has legal authority to impose compliance action requirements and, if warranted, monetary fines. If such enforcement actions are still not successful in restoring compliance, more drastic actions can be taken, including hearings before the Board of Trustees, criminal charges, and severing an industry’s connection to the sewer.

Laboratory analysis is also used as the basis to determine the appropriate charges to be assessed to each industry. Industrial users are billed separately according to their actual wastewater volume and strength. Periodic or random inspections are conducted by the Pretreatment Coordinator and/or Pretreatment Manager. Such inspections are designed to ascertain compliance of an industry with the requirements of the pretreatment regulations that go beyond discharge limitations. Such requirements include proper record keeping and proper storage and spill control of chemicals.

Certain industries are unable to meet their  permitted discharge limitations without performing treatment at their place of business and prior to discharging to the District’s system. These industries are required to provide pretreatment of their waste stream to bring pollutant concentrations down to acceptable and specified levels before releasing them to the District’s system. There are only a few industries within the District that have pretreatment operations. Some operate highly technical pretreatment plants to treat a variety of waste streams including metal plating, cleaning solvents, and other toxic chemicals.

The goal of pretreatment is to prevent hazards to human health and safety, protect the environment, and protect the collection and treatment facilities against plugging and upset that may cause a health risk or violation of the District’s NPDES permit. The District’s program has been successful at reducing and controlling industrial discharges.

The following are the allowable limits given by the North Davis Sewer District 
 

Pollutant of Concern	Unit of Measure	Daily Maximum	Monthly Average	Date Added
pH	S.U	6.5 to 11.0		11/1998
Arsenic	mg/L	0.60	0.10	Original Limit
Cadmium	mg/L	1.66	0.12	Original Limit
Chromium	mg/L	7.00	1.00	Original Limit
Copper	mg/L	1.00		Original Limit
Cyanide	mg/L	0.50		Original Limit
Lead	mg/L	0.60	.025	Original Limit
Mercury	mg/L	0.02	0.01	Original Limit
Molybdenum	mg/L		4.97	11/1998
Nickel	mg/L	4.00	0.60	Original Limit
Selenium	mg/L	1.00	0.08	Original Limit
Silver	mg/L	4.00		6/1995
Zinc	mg/L	4.00	1.50	Original Limit
Oil & Grease (petro.)	mg/L	100		3/1997
FOG	mg/L		500	3/1997
TTO	mg/L	2.13		Original Limit