Stormwater Treatment Systems

Stormwater Treatment with a storage reservoir (tank) or without one if vertical layout permits.

The Stormwater Treatment is usually designed in such a way that the surface wastewater enters the plant by gravity through the stormwater treatment system. Unfortunately sometimes the lay of the ground doesn’t allow for such design.

In this case, the construction of a storage reservoir (tank) is necessary.

A storage reservoir is an intermediate link before the water treatment. It accumulates storm discharge and, at the same time, treats the most heavy suspension by gravitational settling. In this case the storage reservoir is a sand separator. It is usually a part of treatment facilities and serves for the primary large mineral suspension purification of wastewater.

Most often storage reservoirs are made from reinforced concrete where the accumulation of discharge takes place.

The storage reservoirs service consists of sediment removal and equipment check.

The sediment from storage reservoirs is pumped out through the servicing wells by the sludge pumps and disposed of in appropriate locations.

Regular supply of discharge for further treatment is made out of the storage.

Stormwater treatment installations with or without a storage reservoir if vertical layout permits. Stormwater treatment is usually designed in such a way that the rain flow enters water treatment by force of gravity through the stormwater treatment system. Occasionally, the topography of the area will not allow for such facility design.  In such cases, the construction of a storage reservoir (tank) is necessary.

A storage reservoir is an intermediate link before the municipal stormwater treatment. It accumulates storm discharge and, at the same time, treats the heaviest suspension by gravitational settling. In cases like this, the storage reservoir acts as a grit removal system. This stage is a smaller scale version of the sediment separators used at the start of wastewater treatment plant flows to reduce large mineral suspensions. Sediment separators are often found in water purification plants and are used in the initial stages of water purification from large mineral suspensions.

Most often storage reservoirs are made of reinforced concrete where the accumulation of discharge takes place.

The maintenance of the storage reservoirs consists of sediment removal and equipment upkeep, as well as equipment function check.

The sediment from the accumulator pits is removed through the servicing wells by the sludge pumps and disposed of in accordance with the EPA and each State’s governing body, whichever is stricter.

Removal of suspended and petroleum products due to settling and filtration is one of the main methods of treatment. Here, sand and petroleum separators are used as sorption filters.

Sand Separator

To remove sand and other contaminants in suspension, a sand separator is used.

Sand separator activity is based on gravitational separation and sedimentation of suspended solids in wastewater.

Wastewater flows into the tank through the suction pipe, where insoluble pollutants with density of 1500kg / m3 and higher are discharged through the outlet, while the lighter particles are separated on the coalescence module.

In stormwater treatment facilities designed by Bioxica, HELYX sand separators are used.

HELYX Sand Separator

The HELYX sand separator is a cylindrical tank made of glass-reinforced polyester. The tank also includes a well with a ladder. The sand separator and sludge level sensor are serviced through this well. Maintenance of the device consists of periodically removing sand and calibrating equipment. Sand can be pumped out using a sewage truck or sludge pump.

Evacuation must be carried out when sludge fills ⅓ of the sand void volume, or at least once a year.

Wastewater storage pits

The above scheme of the surface wastewater pre-treatment through the sand separator is possible if the topography of the area will allow supplying cleaned wastewater to the sand separator by gravity. Otherwise wastewater storage pits are necessary, which may increase construction cost and operation complexity.

The wastewater storage pits consist of a container, often made of reinforced concrete, which accumulates waste.

Some gravitational sedimentation of suspended solids occurs here also.

Maintenance of the device consists of periodically removing sludge and calibrating equipment.

The precipitate from the storage pits is pumped out periodically through service wells with a sludge pump and is transported for recycling or disposal to designated sites.

The adjustable flow drain is cleaned at this time.

If there is a storage pit, the sand separator is not included in the wastewater treatment plant.

Oil- petroleum separators

The oil-petroleum separator is designed for mechanical treatment and removal of insoluble petroleum products, oils and combustibles out of surface wastewater.

The stormwater treatment facilities designed by Bioxica use HELYX oil-petroleum separators.

Oil-petroleum separators by HELYX can purify wastewater from petroleum products to 0.3 mg / l and suspended solids to 20 mg / l.

Achieving a high degree of treatment is possible through the use of a coalescent structure module that separates particles larger than 0.2 mm, and the lighter suspended solids (less than 1500 kg / m3).

Addition of a coalescence module improves the performance of the oil- petroleum separator compared to similar units by 1.5 due to the large surface area of the modules.

Coalescing modules are made of polypropylene profiled sheets. Polypropylene is a water repelling material that attracts small droplets of oil to the surface where they coalesce to form larger droplets, and then ascend to the surface. Maintenance of the device is worry-free because the coalescing unit is self-cleaning.

For ease of maintenance, it is possible to install a sensor-switch in the oil- petroleum separator, which will activate a light and sound alarm in the case of overflow of petroleum products.

Oil- petroleum separator HELYX

Sorption filters

For discharge on to surface water, strict characteristics must be met. In such cases, post-treatment facilities are used. The post-treatment unit is a tank equipped with a filter which receives the wastewater. Transit of waste through the body of the filter is carried out without pressure. The stormwater treatment facilities designed by Bioxica use Helyx sorption filters.

The sorption filter is a cylindrical container with fiberglass pipes for admission and discharge of water. Dynamic adsorption is used in the filter. It is a process in which the adsorbent solution flows through a fixed adsorbed layer. The natural stone shungite, activated carbon, and a hydrophobic sorbent HEC are used as sorbents. Operation can continue without replacement of this material for over 3 years.

The stormwater treatment system, designed and supplied by Bioxica, according to client's specifications, for volume and composition of treated wastewater, is assembled in multiple or single units (monoblock).

Stormwater sewage in multiple HELYX blocks

Production capacity of the wastewater treatment plant is up to 2400 g/m (150 L / s).

The composition of stormwater treatment facilities in multiple blocks includes:

1. Distribution well;

2. Sand separator;

3. Oil- petroleum separator;

4. Sorption filter;

5. Well for sampling.

All the units are made of fiberglass containers manufactured by filament winding machine.

To prevent displacement during backfilling and under the influence of surfacing groundwater due to lightweight, tie belts made of synthetic non-elastic materials are put in place. Tie belts are affixed to the  sludge pit tank with special lugs, situated on the reinforced concrete plate. The plate is usually made of monolithic concrete.

Distribution well

A distribution well supplies wastewater to the treatment plant in the corresponding amount. The flow of wastewater is separated. The contaminated part of the flow goes to the wastewater treatment plant, and during intensive rain the "conditionally clean" part of the flow goes to the bypass line.

This system reduces the cost of equipment for wastewater treatment as compared to traditional systems.

Distribution wells are produced for different volumes of incoming wastewater: 10-30; 15-45, 20-60; 30-90; 40-120; 50-150; 75-225; 100-300 L / sec (up to 4800 gpm).

Sand separator

Wastewater flows into the sand separator, where the insoluble solids with density of 1500 kg / m3 are precipitated due to gravity. The sediment is removed through an outlet. The lighter particles are separated in further purification. A sewage truck pumps the sludge out through the service well.

A vertical, tangential sand separator, or one with thin-layer modules will have a smaller footprint.

Sand separators are produced for different volumes of incoming wastewater: 1.5; 3; 6; 10; 20; 30; 40; 50; 75; 100; 150 l / s (24 - 2400 gpm).

Oil-petroleum separator (oil separator, oil-petroleum separator, petroleum-oil detector, petroleum-oil separator, gasoline-oil separators)

The oil-petroleum separator is designed to mechanically treat the surface wastewater and remove hard dispersive insoluble matter out, that is a mixture of mineral oil and products of combustion.

The composition of the oil- petroleum separator includes a coalescing unit that separate oil particles larger than 0.2 mm and suspended solids lighter than 1500 kg / m3.

The coalescing module is made of thin-layer corrugated PVC plates glued together.

Usage of the coalescing unit in an oil-petroleum separator can increase its performance compared to similar units by 1.4 times due to the greater surface area of the modules.

One of the advantages of the modules is also their self-cleaning ability.

The composition that can be achieved by an oil-petroleum separator is:

• Petroleum derivatives - 0.3 mg/L;
• Suspended solids - 20 mg/L.

Oil-petroleum separators are produced for different volumes of processing of incoming wastewater: 1.5; 3; 6; 10; 20; 30; 40; 50; 75; 100; 150 l / s (up to 2400 gpm).

Sorption filter (sorption unit, tertiary wastewater)

The sorption filter is a cylindrical container with fiberglass pipes for admission and discharge of water. The dynamic adsorption is used in the filter as a process in which the adsorbent solution flows through a fixed adsorbed layer.  Sorbents in use are the natural stone shungite, activated carbon, and the hydrophobic sorbent HEC.

In this system, replacement occurs every 3 years or longer, with a high degree of purification throughout the period of operation.  Lifetime of the sorbent is determined by the degree of purification at the outlet, and depends on the level of suspended solids, as well as the concentration of oil at the inlet.  With the sorption filter, the purification rate can be: suspended solids - 3 mg / l, petroleum derivatives - and 0.05 mg / l.

Sorption filters are available for different amounts of processing of incoming wastewater: 1.5; 3; 6; 10; 20; 30; 40; 50; 75; 100; 150 l / s (up to 2400 gpm).

Sampling well

A sampling well is used to test the quality of treated water.

Sampling wells are produced for different volumes of incoming wastewater 10; 15; 20; 30; 40; 50; 75; 100 l / s (up to 1600 gpm).

One unit (Monoblock) stormwater treatment plant of HELYX type

Single unit stormwater treatment system characteristics.

The single unit HELYX stormwater treatment plant is assembled as one body and made of composite materials based on fiberglass.

For some types of treatment, the interior is divided into sections

Such treatment facilities are used, as a rule, in cases when there are restrictions on the areas of infrastructure.

Material and labor costs in the manufacturing, construction and installation works of one unit systems are less than that of multiple blocks.

But for all the apparent advantages of monoblock treatment plants, they require a more careful approach to the work on adjustment and operation.

Bioxica designs and supplies single unit (monoblock) or multiple fiberglass HELYX treatment systems. The single unit treatment system capacity is up to 100 L/s (1600 gpm). The single unit treatment system tech-line capacity is up to 150 L/s (2400 gpm).

For larger volumes of wastewater, the treatment facilities are installed in several production lines.

At the head of the treatment facilities, one common distribution well is installed to distribute wastewater to technological lines.