For construction, tunneling, or excavation sites to remain safe and productive, dewatering is crucial. Strong dewatering filtration is necessary for the efficient handling of water pumped from excavations, whether it be process water, groundwater, or rainwater, particularly when releasing to regulated waterways or environmentally sensitive areas.

When would dewatering and filtration systems be used?

Anytime water runoff or accumulation could release pollutants like oil, hydrocarbons, or sediments into the environment, dewatering and filtration systems are crucial. Before releasing these pollutants into navigable waters, facilities are required by the Clean Water Act to filter them. Federal regulations also mandate that facilities and storage locations undergo routine inspections for dangerous materials, and that countermeasures be put in place right away if contaminants are discovered. Industry-leading dewatering and filtration products from Basic Concepts, including filter bags, oil-water separators, portable treatment systems, and smart textiles like Agent-X, help operators comply with EPA and SPCC regulations while simultaneously shielding sites from pollution.

Evaluating the Source of Water Quality

Assessing the source water quality is the first step in creating a dewatering filtration plan. Engineers usually check for suspended solids, turbidity, pH changes, and the presence of chemical or oil contaminants. For example, water from grout-rich areas might have high pH values, necessitating specific care such as pH neutralization. Project teams can choose the best filtration techniques once they have a clear understanding of the physical and chemical makeup of the water.

Methods for Dewatering Construction

The construction industry employs a number of dewatering techniques, such as the following:

Dewatering at Wellpoint

A number of tiny wells spaced uniformly along an excavated area are used in the wellpoint method of dewatering. Every wellpoint is connected to the main pipe, which transports the water to a designated discharge area via a high-efficiency pump.

Dewatering of Eductor Wells

Eductor well dewatering is an additional method of water removal. Using this technique, water flows through a sequence of small-diameter wells with nozzles driven by pumping stations. Since eductor well dewatering has no suction lift limits, it is frequently used on deep excavation job sites.

Dewatering Sump Pumps

The most popular technique for draining water from a construction site is sump pump dewatering. In order to collect groundwater and then direct it to an appropriate discharge area, workers dig temporary pits known as sump pits. Sites with a lot of sand or gravel and shallow excavation are ideal for this technique. It is the most straightforward and economical dewatering method.

Dewatering Deep Wells

Dewatering a deep well is a little trickier. Since water must be removed from beneath an excavation, a higher pumping rate is necessary to move the water to discharge sites effectively. Unlike other vacuum-powered dewatering techniques, each deep well has a submersible pump that pushes water forward rather than pulling it.

Common Filtration Approaches

1- Bags for filters

Filter bags, which are made of geotextile materials, fit onto discharge hoses and catch sediments while letting clear water flow through. The capacity of the bags varies, and when clogging reduces flow, operators need to clean or replace them. As a first line of defense against turbidity, filter bags stop habitat damage and erosion downstream.

2- Sediment tanks (also known as settling or weir tanks)

Gravitational separation is used in all cartridges and tanks. For example, a multi-chambered sediment tank holds water inside weirs, allowing particles to settle out before clear water is released. On small jobsite footprints where lateral spread is impossible, these are extremely helpful. They are portable and efficient due to their modular design.

3- Systems of Active Treatment

Targeted engineering is needed to remove more difficult contaminants, like oily water:

Separation of oil and grease: Hydrocarbons and other non-aqueous pollutants are cleaned by oil-water separators.

Bio-coagulants: used in chitosan-enhanced sand filters to bind fine particles and pre-treat water before it passes through the filter.

pH control and oxidation units: These ensure adherence to EPA limits (<0.30 mg/L iron, 0.05 mg/L manganese, <5 NTU turbidity) by reducing suspended iron or manganese and mitigating alkaline grouting or acidic trench water.

Pump Selection and Control of Flow

Consistent pressure and flow rates are necessary for efficient dewatering filtration. For raw, unfiltered water, trash pumps that can move solids are frequently chosen because they are resilient in challenging on-site circumstances. Electric submersible pumps that operate with precise filtration setups are better suited for active systems or filtered water. Continuous operation depends on matching the pump’s capacity to the anticipated discharge volume (such as wellpoints or storm events).

Recycling and Temporary Retention

Onsite retention, such as holding tanks or retention basins, is essential when offsite discharge is not practical. Depending on the quality and regulations, the collected water may naturally evaporate, return to the on-site soil, or be used again for dust suppression, irrigation, or compaction.

If water is eventually released, filtration must also be a part of retention systems.

Best Management Practices

Best management practices (BMPs) pertaining to water concentrate on problems with water quality brought on by land development. When creating a dewatering plan, there are many BMPs to consider in addition to filtration on the jobsite. BMP choices consist of:

Vegetative buffers: To slow runoff and stop soil erosion, plant vegetation or install vegetative buffers alongside water bodies.

Silt fencing: an inexpensive way to temporarily manage runoff and sediment on construction sites. In order to create a fence on a downhill grade, geotextile fabric is stretched between wooden stakes, trapping sediment while letting water pass through.

Berms: A transient ridge made of stone, gravel, or crushed rock that redirects water to a designated path and slows and filters runoff to stop erosion; and

Retention basins: structures made to temporarily store runoff, stop localized flooding, and hold back sediment-laden runoff from disturbed areas until the sediments have had time to settle out.

Because storm water management is an ever-evolving field, BMPs frequently undergo changes. While creating a site dewatering plan, always consult the EPA and your local agency for the most recent rules, permit requirements, and best practices.

Conclusion:

Ensuring regulatory compliance, preserving ecosystems, and preserving jobsite safety all depend on a well-designed dewatering filtration system. Before discharge, suspended solids, pH imbalances, and contaminant levels can be considerably decreased by using techniques like filter bags, sediment tanks, and active treatment, which includes oil separators and chitosan-enhanced sand filters. Performance is maximized and environmental impact is decreased by selecting the right pumps and designing retention or recycling systems. Pollutant migration and erosion are further reduced by incorporating best management practices like berms, silt fencing, and vegetative buffers. Contractors can efficiently oversee dewatering operations and protect project results and local water quality by coordinating design with NPDES and the Clean Water Act.

To explore the latest innovations in water and energy technologies, and discover a wide range of products and solutions from around the world, you can visit the virtual exhibition AQUA ENERGY EXPO which featuring leading companies in water treatment, desalination, and sustainable energy through the following link:
https://aquaenergyexpo.com/