Pump and Treat

Introduction/Principles

The majority of contaminated sites in the UK contain impacted groundwater that requires treatment during remedial works. Groundwater can be abstracted from open excavations, boreholes, trenches, eductor and ejector wells, or even cut off trenches and pumped to a water treatment facility where contaminants are removed from the water. Clean water can then either be discharged to a trade effluent sewer, recycled for use on site such as dust suppression or re-injected back into the site with appropriate approvals.

Contaminated groundwater contains three phases of contamination:

Contaminated suspended solids
Dissolved phase contaminants
Free phase contaminants

Groundwater treatment is usually combined with other remediation processes such as dual (multi) phase extraction , ex-situ bioremediation or excavate and dispose. Additionally many remediation processes produce liquid waste streams that require water treatment such as leachate from ex-situ bioremediation or abstracted effluent from dual phase systems. A pump and treat approach can also be used as a treatment system in its own right should the site have other constraints limiting remediation options or if the site and client requires a longer timescale remediation.

Contaminants

Groundwater treatment plants are specially designed for individual sites, a water treatment plant can be designed to cope with almost any contaminant or combination of contaminants. Common contaminants of concern in groundwater requiring treatment include but are not limited to:

Diesel range organics (DRO)
Petroleum range organics (PRO)
Volatile and semi-volatile organic compounds (VOC, SVOC)
Hydrocarbons
Heavy metals (lead, chromium etc)
Pesticides
pH

Plant Description

Water treatment plants are often specifically designed for individual contaminated sites therefore there is no defined set of equipment or plant description. Common plant equipment associated with groundwater treatment plants includes:

Abstraction pumps
Groundwater storage tanks
Control systems
Granular activated carbon (GAC) pods
Oil/water separators
Lagoons
Settlement beds/tanks
Baffle tanks
VOC strippers
Dosing pumps
Buffer tanks

Example

The majority of VertaseFLI remediation works have involved water treatment of groundwater plumes and/or dewatering of excavations. Due to these requirements VertaseFLI designs its own modular water treatment plants (WTP) so all of our treatment plants are adaptable to almost any contaminant.

VertaseFLI was commissioned to design and construct a WTP capable of treating water from a VertaseFLI designed dual (multi) phase extraction system and water from civil engineering excavations.

The water treatment plant ran on site for 6 months, during which time the plant was successfully increased in capacity to accommodate additional excavation works. The plant consisted of a number of units including a settlement tanks, oil/water separator, GAC units, pumps and hosing, the unit was fully automated and ran successfully for the duration of the project. Treated water was discharged under a trade effluent license to a local waterway under a stringent discharge consent, which included weekly laboratory analysis of treated waters. In total over 3.2m litres of groundwater was treated and 1,000 litres of free product was collected.

Advantages and Limitations

Advantages:

Can be designed to remediate almost all groundwater based contaminants
Proven track record on UK contaminated sites

Limitations:

Only treats groundwater
Can be expensive depending on contaminants and discharge consent agreements
Additional by-products required disposal (sediments, spent GAC pods, etc)
If used alone can have lengthy timescales

A great set of people with a good attitude all around. The site was managed very professionally, I never had to intervene once on a H&S matter, which is very unusual!

Daniel Barnes

Project Manager, Balfour Beatty

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