Mechanical Screen for Goolwa Waste Water Treatment Plant (WWTP) – Construction

⁠⁠⁠A new dedicated mechanical screen is required to be constructed at the existing Goolwa WWTP.

The new mechanical screen is required to cater for wastewater flows received and must provide an ability to ‘screen’ all incoming wastewater flows; to remove hard contaminants from water flows, prior to processing. In general, users of a wastewater system will discard foreign objects into the wastewater network via drains, toilets etc. These items must be removed.

The new mechanical screen shall generally be;

• New dedicated package mechanical screen, including screw (or similar) mechanical screen, pipework, valve pits, foundations, access platform and all other ancillaries as required
• Connection to the existing Goolwa WWTP pipe work
• Removal of any redundant equipment from site
• Provision of any ancillary plumbing work and blank conduit runs, to house future electrical works
• Reinstatement of surfaces affected by the new service installation works
• Provision of ‘as constructed’ survey and drawings
• Mechanical screen to be as per drawing and specification

As a Council owned & operated wastewater network, Council requires that a number of Special Conditions apply to these works;

• The scope excludes live connection to existing electrical power supply to service the new mechanical screen. The new power connection shall be installed as a separate package of works and be under the supervision of Council’s wastewater Electrical Engineer.
• The successful contractor IS required to install blank conduit from the new mechanical screen, to the existing power feed location. The successful contactor will make allowance for runs of orange HD electrical conduit, as shown on plan. The installation of these blank conduits will be part of these works and placed in the locations deemed necessary by Council;
• The placement of electrical wiring (live) to operate the new mechanical screen will occur at a later date, likely to be 3 to 6 months after the completion of civil works;
• Once electrical feed has been installed, Council’s wastewater Electrical Engineer will test & commission, in conjunction with the successful contractor, the new mechanical screen and all associated works;
• The successful contractor shall make allowance to re-visit site to assist commission the new mechanical screen at that time.

Mechanical Screen

• The screen shall be inclined filter screw screen type. The screen shall combine screening, conveying, washing and dewatering of screenings within a single unit. The screen shall include the following elements:
• Prefabricated screen chamber;
• Perforated half pipe screen;
• Shaftless spiral screw conveyor;
• Screenings washing system;
• Drop chute from screening outlet to collection bin;
• Local termination panel; simply a stainless steel box that has a terminal strip installed with the control elements (level sensors, solenoids etc.) pre-wired to it. No control system (ie: PLC unit, relays, timers etc.) are required;
• Inlet and outlet pipework to connect to the existing system, isolation valves, control valves and pipework joints;
• The screen capacity shall be at least 60 L/s of typical municipal wastewater.

Local Termination Panel

• The Contractor shall supply a machine with all of the required input and output transducers pre-wired to a stainless steel marshalling/termination panel to be confirmed with the CWMS electrical engineer to enable Council to connect these devices to the existing main/central “Melsec” PLC system digital input & output points located within the existing control room. The 3 x phase drive motor is to be simply left mounted & unterminated.
• In consultation with the CWMS electrical engineer the Contractor is to identify all cabling within the marshalling/termination panel via approved cable markers & provide a simple schematic diagram reflecting these circuits.
• Council shall develop & install the required PLC system software as per the sequence/control specifications to be supplied to Council by the Contractor.
• Council shall integrate the units hardwired emergency stop system into the sites existing hardwired emergency stop system.
• Council shall install all of the necessary power & control cabling between the unit & the existing control room.

The Council is supportive of tenders considering and utilising the services of local suppliers, providers and trades for all aspects of the project. Tenders shall document those nominated specialists, suppliers and trades within their package and fee proposal.

It is important to note that the Council requires this project to meet with a maximum construction budget. 

Briefings: A briefing session will be held at CWMS - Waste Water Depot, Skewes Road, Goolwa, SA, Australia 5214 on 3:00PM 16 March 2020