Gunalda, Queensland


Kubota HCZ


Consult, design, and construct STP

When a new onsite wastewater treatment system failed at Gunalda Service Station, True Water stepped in to help find a solution to the problem. The sewage treatment plant designed and installed by another company failed within 18 months of installation and was not treating the effluent to the required standard. In fact, the system had not met the required Environmental Authority (EA) discharge limits since its construction. United Petroleum sought the expertise of the True Water team to assess options for providing an immediate and long-term solution that meets the EA licensing conditions and adheres to project lifecycle objectives.

Gunalda Service Centre is located on the Bruce Highway which connects Gympie and Maryborough. It’s approximately 30km North-West of Gympie and receives a high volume of traffic. Currently, the service centre consists of a large food court containing 350 seats, 90 parking lots along with a separate trucker’s lounge. The waste generated from Gunalda stems from the site amenities, kitchen, and laundry facilities.

The site does not have a mains water supply, utilizing rainwater for all non-potable purposes and tankering in potable water for consumption purposes. This affects the influent strength which is already high due to the nature of service station wastewater.

Assessing the site to identify the best solution

True Water’s specialist consultancy team was asked to assess Gunalda’s failed onsite wastewater treatment system. After conducting a thorough assessment of the site, True Water found the design had multiple points of malfunction. The assessment revealed evident signs of overflows in the STP with a severe build op of solids and untreated sludge. The grease trap had accumulated excess oils and grease with the trap no longer removing grease from the treatment train. The components of the system were not functioning as intended and the wastewater was not being treated.

Additionally, the undersized effluent disposal area was unable to meet the operational, hydraulic, and nutrient requirements of the site. It was poorly installed with large rocks in the lateral trenches and components placed in a way that the system lacked the velocity to flush the laterals.

The client had been forced to put a pump-out schedule in place to remove wastewater from the site and pay to have it delivered to a municipal sewage treatment plant. As a long-term solution, the prohibitive costs and uncertainty around ongoing acceptance by the municipal plant meant continuing to pump out was not viable.

Furthermore, although individual parts could be fixed, a cost assessment showed that repairing the system would incur substantial costs. With no guarantee that the original system would be able to manage the wastewater load. The cost involved in removing from the site and disposing of the failed STP was substantial due to its size and condition. True Water recommended that the existing STP be cleaned, decommissioned, and left in place.


Completed wastewater treatment system at Gunalda Service Station

True Water installs onsite wastewater system designed to last

Due to the severity of the issues, the ongoing failures, and the inadequate system design, True Water was engaged to design and install a new fit-for-purpose wastewater treatment solution.

True Water designed a site-specific solution that is suitably sized for the expected wastewater flow. The new system treats and disposes of the wastewater on-site whilst meeting the operational requirements.

It’s important to consider the future expansion of the site and design a system that can stand the test of time. Based on the information attained during the consultancy phase, True Water installed a Kubota HCZ to provide Class B treatment. The effluent is then dispersed to a suitably sized sub-surface drip irrigation field. The new system is configured to receive up to 30kL/day with the flows to the treatment system being managed via an EQ Chamber.

True Water provided a wastewater solution that includes inflow buffering capacity to manage influent flows and strength. The primary buffer storage captures the wastewater before it enters the Kubota treatment plant. It helps to regulate the flows going into the treatment system and provides a buffer for high-volume flow periods. Due to the limited water supply, the concentration of the influent entering the system is high. The primary buffer storage is also designed to mix the wastewater flow. This is to ensure the high concentration influent from toilets is mixed with wash water before it enters the treatment system.

A new system that is out of sight and out of mind

The original STP was large, noisy, smelly, and placed right next to the service area where it impacted visitors. True Water values amenity and specializes in wastewater solutions that fade into the background. The new True Water system is installed behind and down a slope from the service station. The modular Kubota sewage treatment systems are underground and serviced via gas-tight access lids. The customers of the United Gunalda Service Centre are unaware of the system and that’s the way it should be.

In order to meet the requirements of the project, True Water replaced the failed onsite wastewater treatment system and irrigation that had previously been provided. The replacement system is reliable, simple for staff onsite to manage, and provides a high quality of water treatment. In addition, Kubota systems have no internal moving parts. This means they don’t require chemical dosing systems as part of the treatment process. This reduces operational and maintenance costs.

What happened at Gunalda’s service station highlights the importance of engaging a wastewater treatment specialist. By contacting consultancy specialists, we can design a system that meets all of your project requirements. True Water provides a unique service in the industry.  Our team specializes in all aspects of delivering onsite wastewater treatment solutions. From consultancy and design to installation and management. Contact our team today to discuss your project needs.

Contact the team at True Water for a great solution for your own unique property.

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