Planning a Groundwater Treatment Project - Design Considerations
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Treatment System Design Considerations
Understanding the flow, water quality, duration, and space available is critical when designing an effective treatment system to meet water discharge quality requirements.
Flow Rate - How much water will be discharged?
Flow rate is necessary to determine media requirements and the size of the system. Flow rates are estimated during the dewatering system design process using the project and hydrogeologic information available.
Typical dewatering systems provide a constant stream of water that’s treated 24/7. However, other factors may need to be considered depending on the project. The following questions should be asked if flows are intermittent or there are other sources of water:
Intermittent Flow
- Anticipated volume per day?
- Operating hours per day?
Total Flow
- Additional sump pump flow?
- Rainfall considerations
Water Quality
Knowing water quality is necessary for determining the treatment needs. Influent water quality and effluent discharge standards dictate what contaminants need to be removed. Certain media types may require additional testing to evaluate constituents that will affect the media’s ability to effectively provide treatment.
Water quality information can be collected through the following activities:
- Perform water quality analysis using one or more monitoring wells on-site
- Conduct a pump test and take water samples from an actively pumping well to ensure influent water quality is accurate
- Test samples for constituents of concern in the permit & others that may hinder the treatment process, such as iron, manganese, & suspended solids
Duration of Discharge - How long will the discharge last?
Knowing the duration of the project is required to calculate the life of media bed.
Other considerations when it comes to project duration are:
- Seasonal changes may impact flow
- Duration can impact permitting
- Discharge fees can impact decisions regarding treatment & discharge points
Discharge Point - Where to discharge water?
Understanding the discharge location will have a significant impact on the amount of treatment required prior to discharge. Some potential discharge locations and considerations are:
Onsite holding/Recharge features
- Contains the water on-site which may expedite permitting process
- Requires space & appropriate geology
- May be limited on discharge capacity
- Recharge systems can be difficult to implement and maintain
Sanitary or Storm Sewer
- Typically easy to locate and utilize in urban settings
- Likely requires a permit
- Discharge fees are typically charged per unit volume of water
- Limited on discharge capacity depending on size of sewer pipe
Surface Water Body
- May have a higher discharge capacity
- Likely requires a permit
- Erosion control measures may be required
Space Available On-site
Availability of space on site is crucial, and you must plan for the area to accommodate the required system. Space on-site dictates if media will be sized for the entire duration or will need to be exchanged periodically during the project.
Typically, the higher the flow rate, the larger the footprint necessary. Consideration to site logistics or the impact of the treatment system setup/weight on the excavation/shoring should be made.
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