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Construction of Industrial Wastewater Pretreatment Systems

In accordance with s. 281.41, Wis. Stats., and ch. NR 108, Wis. Adm. Code, plans for wastewater pretreatment systems that discharge into publicly owned treatment works must be submitted to the Department of Natural Resources for review and approval. Department approval must be obtained prior to construction of a proposed pretreatment system.

Guidance for plan and specification submittals

Pretreatment plan submittals should be mailed to:

Jason Knutson
Wastewater Section Chief
Wisconsin DNR - WQ/3
PO Box 7921
Madison WI 53707-7921

One copy of each of the submittal requirements for DNR review should also be transmitted to the local municipality for their review and approval.

A complete description of the content and recommended format of the engineering report is provided below. The plans or the engineering report should include:

  • A general project location plan drawing.
  • A schematic flow diagram including treatment units, monitoring and control devices, and all piping with pipe content and flow direction indicated.
  • Plan drawings (to scale) indicating existing and proposed collection, treatment and monitoring and control equipment. Piping should be labeled to indicate pipe content and flow direction.

The department plan reviewers will evaluate the submittals to ensure that accepted engineering practices are used and that the proposed system design is appropriate for the type of industry and applicable pretreatment regulations. Reviewers will also check for suitable sampling provisions and design features to ensure operational reliability. The department does not have specific codified design criteria for pretreatment systems.

Once the submittal is determined acceptable, a department approval letter with one set of plans and specifications (with department approval stamp) will be mailed to the pretreatment system owner. Copies of the approval letter will also be sent to the municipality owning the sewerage system receiving the discharge and to the design engineer.

Guidance for pretreatment system engineering reports

Pretreatment system plan submittals should include the following information. Please be concise and arrange the information in an orderly format. This will greatly assist the department in conducting the review and in preparing the approval letter.


Engineering report for a wastewater pretreatment system for [insert name and location of industry]

General Information: Provide executive summary of proposal submitted for approval and include any special circumstances or relevant information not covered by report sections listed below.

Company Contact:
Name of Person, Title
Company Name and Address
Telephone Number
E-mail Address

Name of Person, Title
Firm Name and Address
Telephone Number
E-mail Address

The person, or persons, responsible for preparing the plans, specifications and engineering report should be indicated. Plan preparers should indicate if they are registered professional engineers in the state of Wisconsin. If not a professional engineer, the plan preparer should describe their relevant experience and qualifications (submittals are not required to be provided by professional engineers except when the department determines that a pretreatment facility may affect public health or safety).

Products manufactured: Describe the products manufactured at the facility and the processes and raw materials used.

Wastewater: Characteristics should include information such as flow rates and key contaminants, particularly those that are being regulated. Describe the type of wastewater to be treated (sanitary, contact cooling, non-contact cooling, process), and identify any combined waste streams or side streams. Describe the final discharge or use of treated wastewaters, i.e. sanitary sewer, storage for truck hauling off-site or process recycle.

Need for pretreatment: Briefly describe why the pretreatment system is needed and whether this is a new system or a modification to an existing system. List the specific numerical standards the system is designed to meet. If the wastewater is subject to federal standards, cite the applicable 40 CFR Standard or Wisconsin Administrative Code.

Description of system: Briefly describe the pretreatment system and the wastewater to be treated. Indicate the design flows (gallons/day) and key contaminants, as well as the actual flows and loading anticipated. The plans and specifications, or the engineering report should contain a general project location plan, and a schematic flow diagram including treatment units, monitoring devices and all piping. Pipe contents and flow direction should be indicated.

If new or innovative equipment or methods are proposed in the plans, sufficient data based upon practical application, experimental or otherwise, shall be submitted to show that satisfactory results can be secured.

Sludge removal and disposal: Describe the anticipated methods of removal, handling, and disposal of wastewater treatment sludges and their filtrate recycle. Some sludges are considered to be hazardous wastes and subject to special disposal regulations. Disposal of sludges on land may require a WPDES discharge permit. It is important that the plans provide ready access for removing sludge accumulating in the pretreatment system and provides for removal of sludge without taking the system out of service.

Sampling: Describe the provisions made to sample the wastewater, including the pretreated effluent flow monitoring and sampling equipment and frequency. Provisions should be made for a representative monitoring point such as a manhole that is accessible to city, DNR and EPA regulatory persons.

Project implementation schedule: A brief project implementation schedule should be provided.


  • Include any flow schematic or other drawing not included as part of plans.
  • Include any relevant correspondence from municipality or other agencies.