Harlequin Commercial Sewage Treatment Plants

Sewage treatment plants are fast becoming the sewage management system of choice for situations where a connection to a main sewer is either unavailable or not viable. This is because a sewage treatment plant removes liquid effluent from the sewage and cleans it to a degree that makes it safe to release into watercourses. It is said to be so clean that you could drink it without further treatment, although we haven’t heard of anyone willing to try it!

This brings significant benefits to off-grid sewage management: less risk of polluting the environment, and as a large percentage of the sewage is removed, the remaining sludge requires emptying less frequently, resulting in savings in costs and carbon footprint.

By and large, sewage treatment plants are designed for single properties or small groups of properties, but three new ranges of commercial-scale treatment plants from Harlequin enable water boards, utility corporations, housing associations and facilities companies to benefit from this environmentally friendly and cost-efficient technology.

Where are Harlequin commercial sewage treatment systems typically used?

With their low noise impact and fully secured unobtrusive manhole covers, Harlequin commercial sewage treatment plants are ideally suited to commercial applications such as caravan parks, hotels, commercial building sites, retail stores, campsites, cafes, restaurants, schools, garden centres, etc.

How do Harlequin’s commercial sewage treatment plants differ from smaller versions?

Strength and stability

In general, smaller sewage treatment plants are manufactured from rotationally moulded plastic or fibreglass (GRP). When properly buried and supported underground, this gives them the required strength and durability for domestic applications.

Harlequin commercial plants are manufactured from Sheet Moulding Compound (SMC) panels which offer greater structural stability and strength. They also feature a flat base, making them more stable during storage and transportation.

Maximised bacterial activity and water quality

While all sewage treatment plants pump air through the liquid effluent to encourage the bacterial growth required for treatment, Harlequin commercial plants feature a unique Moving Bed Biofilm Reactor (MBBR) system which maximises bacterial growth, with no fixed media to cause system blockages.

They are also fitted with external blower units, which are used in the secondary treatment phase to create air bubbles for aeration and agitation.

Aeration provides usable oxygen to promote bacterial growth through a higher concentration of microorganisms. This is provided through high-volume, fine bubble diffusers. Agitation stirs the liquid effluent to keep waste particles in suspension throughout and expose them to the microorganisms that remove them from the water stream.

This means that Harlequin commercial systems exceed the acceptable effluent quality standards of 20 mg/l biochemical oxygen demand (BOD), 30 mg/l suspended solids and 20 mg/l ammoniacal nitrogen.

Safety and easy maintenance

Harlequin commercial treatment plants are fitted with fully secure, unobtrusive pedestrian-duty manhole covers to enable easy access to each chamber. The number of covers fitted varies according to the size of the tank.

They also contain very few mechanical moving parts or electrical components for safer, easier maintenance.


While Harlequin commercial sewage treatment plants are manufactured in a range of standard sizes, their construction enables customisation to suit the requirements of individual projects.

What are the Harlequin commercial sewage treatment plant options?

Harlequin offer three commercial sewage treatment plant ranges. The chief difference between the ranges is their capacity, although other variations are required to handle the differing demands of these capacities.

All Harlequin commercial plants are fitted with a linear diaphragm blower unit, one or more alarms, air hose, electrical connections and a control kiosk unit.

Harlequin HPOC range

This range covers Harlequin’s smallest commercial sewage treatment plants, with tank capacities designed for populations of up to 70 persons.

Harlequin HPDE range

The HPDE range covers Harlequin’s mid-size range of commercial sewage treatment plants, where populations range from 70-130 persons. Above 100-person capacity, HPDE plants feature additional side channel blowers and an individual blower box.

Harlequin HPDD range

The HPDD range covers Harlequin’s largest-capacity commercial sewage treatment plants, suitable for populations of 120-600 persons. Models with a capacity of up to 300 persons also feature additional side channel blowers, while above 300 persons the entire plant can be custom-designed to suit individual requirements.

Like to know more?

To find out more about Harlequin commercial sewage treatment plants, contact us at 01953 665940 or email sales@tanks-uk.com to get in touch with our expert team of advisors.

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