Sediment Management (Primary Treatment)
Sediment management during dewatering projects is a necessary first step. Without the effective separation of solids from the liquid stream, all secondary treatment technologies are limited in their effectiveness and often become prematurely fouled due to sediment loading.
Particulate filtering is the most common technique used to reduce Total Suspended Solids (TSS).
It is SCG’s belief that the proper management of sediment benefits all parties. Efforts made to minimize sediment at the source (within the excavation) are imperative, and will provide best value for the project team.
Managing Elevated Contaminant Concentrations (Secondary Treatment)
Once the suspended solids have been reduced, secondary treatment, targeting the contaminant, can be effectively undertaken.
When considering secondary treatment options, it is crucial to understand the type and concentration of contaminant present.
Secondary treatment focuses on soluble contaminants, which must be identified by laboratory analysis. For the purpose of this document, we are referring to petroleum hydrocarbons only.
Petroleum hydrocarbons range from the lighter more soluble volatiles (e.g., BTEX, gasoline), to the heavier less soluble types (e.g., fuel oil, crude oil, bunker fuel).
Treatment options should be specifically designed to treat the type and concentrations of hydrocarbons present. These options include, but are not limited to: air strippers, granular activated carbon, and activated clay.
SCG has vast experience with remediation system design, operation and optimization. We have been providing our expertise and services to numerous clients, with a variety of project requirements, throughout North America for over 25 years.
Excessive Flow Rates
When designing a groundwater treatment system, flow rate is often the most difficult parameter to identify in advance. It is determined by local hydrologic conditions, seasonal precipitation events, and the required depth and extent of the excavation.
Predicting the maximum flow rate from an excavation is often best done through a combination of understanding of the geologic conditions and local experience. SCG has conducted 100’s of dewatering projects throughout Atlantic Canada, which, combined with our strong understanding of local geologic conditions allows for effective treatment designs.
SCG has provided treatment systems within Atlantic Canada with flow rates as high as 3000 L/min, with costs as low as $0.0015/litre.
Strict Onsite Discharge Criteria
The criteria for discharging treated effluent water are dependent on the method of disposal. Options may include surface water discharge and discharge to local sanitary or local storm sewer.
The selection of the disposal method may determine the level of treatment required from the system. This decision may have a significant effect on treatment costs for the project. Typically, discharge to a surface water receptor is the most stringent and will require an aggressive sampling regime.
Storm sewer discharge is typically less stringent but may also have rigorous sampling requirements as part of the discharge approval. There may also be limiting covenants surrounding flow rates during high precipitation events (this is often the time where the requirement for dewatering is at its highest).
Sanitary sewer discharge is the least stringent of the options. There are often limited sampling requirements, but restrictions on flow rates may be required. Finally, discharge to sanitary will usually have fees associated with the volume discharged.
The decision on where to discharge should include all the above considerations, in order to make the best decision for the project.
SCG’s design team has more than 25 years experience in dealing with a variety of site conditions throughout Atlantic Canada. We are ready to assist with our innovative solutions, as part your project team.