Bitumen Asphalt Water Treatment

Enviro Concepts is a leading manufacturer of modular, above-ground washbays and wash down wastewater treatment. For one of our clients, we created a purpose-built, environmentally compliant system for their asphalt/bitumen equipment and truck wash down wash bay. In this case study, we look at some of the challenges that our system solved and highlights from the project.

Challenges

For companies involved in cleaning asphalt and bitumen trucks, tanks and equipment, there is a high input cost of cleaning as well as disposing of the trade waste generated from the wash down process. Most asphalt wash downs use kerosene as a degreaser. The wastewater therefore has high levels of kerosene and bitumen that pose serious threat to the environment and more so to wash staff health.

EPA and council regulations state that proper design, operation and maintenance of water pollution is required for asphalt plants. Water has to be collected and prevented from going down the stormwater stream or anyway to the environment. Even discharge to sewerage system requires high levels of filtration in order to remove hydrocarbons in water. Flammable goods in water can cause explosions in sewers. The wastewater from washing of vehicles and equipment must be directed to sewerage system under stricter than usual conditions of a trade waste permit, or collected for recycling. The only other option is that wastewater be collected and removed by a licensed removalist, which adds to long term, ongoing costs for the client.

We proposed our above ground wash bay waste water treatment system to our client. It was designed to follow council guidelines and provide the most efficient and cost effective solution for washdown compliance. We also specified a portable bay to help reduce the overspray which would affect the neighbouring environment, etc.

Enviroconcept, wash bay, bitumen, asphalt

Project Requirements

 Enviro Concepts had to fulfill 3 primary requirements of the project:

  • A modular washbay that the client was fully able to relocate to the next facility.
  • Fully containerised, close-looped wash water recycling system.
  • A seamless process of installation, commissioning, training and hand-over.

The design for the portable wash bay with heavy-duty washpad, walls and ramps were custom designed to wash trucks and heavy vehicles onsite. Built to withstand large trucks, the washbay was made of hot-dipped galvanised steel to ensure robustness and durability of the wash bay.

In the system designed for the client, the wastewater goes through 3 phases.

After wash, the wash water containing primary solids like dirt, sand, silt, clay and gravel was allowed to flow into the side gutter of the washbay for collection. In wash bays where heavy solids are present, the introduction of a Solids Reduction System is highly recommended. The polluted wastewater is picked up from the side gutter and put into an above-ground solids settling tank. Once the primary and secondary solids are removed, the wastewater is put through an oil water separator (OWS). This removes most of the kerosene and hydrocarbon byproducts of the bitumen.

Due to the extreme nature of pollutants in the waste stream, the next stage of design includes a Dissolved Air Flotation (DAF) system. The system uses coagulation and flocculation chemicals to process the remaining oil and grease as well as carry out removal of suspended solids. At the heart of Dissolved Air Flotation is a mixing tank where the process is fundamental to the system’s high performance. In the mixing tank, air bubbles are generated when a stream of treated water is introduced and pressurized. The fine micro bubbles of air generated in the DAF combines with the insoluble contaminants in the wastewater and lifts them to the surface. In the photograph below, you can see the client’s DAF where the mechanical scraper is in the process of removing the floating sludge layer as the purified water is released for the next part of the filtration process.

Enviro Concepts, Dissolved Air Flotation

After the DAF, the water is then taken through an Enviro Concept Wash-Water Recycle and Polishing plant. The water makes multiple passes through a targeted deep-bed media filtration module. This module is placed at the end of the recycling plant so that it allows a continuous recirculation and polishing of water. This is where the water is disinfected and taken through pH balance ensuring it is safe. Water is then made available as a compliant feed supply for wash bay pressure cleaning process.

Together, these separate filters create a state of the art, high capacity industrial wash-water filtration, treatment and recycle system.

enviro concepts, wastewater, bitumen, asphalt

Filtering and cleaning wastewater from vehicles and equipment in asphalt and bitumen factories has a high degree of difficulty. However, our system is able to process and treat the water rendering it safe for reuse. The photos above show the wastewater during and after treatment. The recycling plant we used saves ongoing input water costs as well as long term costs of having the water removed. Both the washbay and water treatment systems meet compliance requirements. The entire system was installed in a matter of days, training was provided and the project handed over to the client, all within a week.

If you have any questions about a wash bay or water treatment project, send your query to us and we will get back to you within 24 hours.