Sinclair Knight Merz wins 2013 PACE Zenith Award for Water & Wastewater

PACE Zenith Awards 2013: Water & Wastewater category sponsored by Bürkert Fluid Control Systems

WINNER: Sinclair Knight Merz
Project: Critical Portfolio Work Program Goodna STP Upgrade Stage 4A

In order to rehabilitate and protect the Brisbane River catchment, Queensland Urban Utilities (QUU) saw that the Goodna Sewage Treatment Plant (STP) required a significant upgrade to meet not only the identified future demand for wastewater services of the region, but also to meet stringent effluent release license limits which will come into effect in 2013.

The Goodna facility required leading edge automation to enable and monitor the required outcomes. Sinclair Knight Merz (SKM) was engaged to provide multi-disciplinary engineering design services, including process, mechanical, civil, electrical, instrumentation and control for this upgrade of the Goodna STP.

To achieve the outcomes of the Goodna STP upgrade project, SKM identified the need for an integrated solution which would both allow for increased treatment capacity and improved plant performance to meet the imminent implementation of stringent license conditions.

The solution would be the implementation of a sophisticated monitoring and control system. To ensure compliance, sewage treatment plants usually design in effluent criteria which is lower than the actual licence limit where adopted. In the case of Goodna STP, this criteria stipulated Total Nitrogen (TN) of 2.5 mg/L and Total Phosphorus (TP) 0.8 mg/L.

To achieve such low TN and TP concentrations within the final effluent, the plant utilises a Membrane Bioreactor (MBR) configuration consisting of final stage membrane ultra-filtration within a 5 Stage Bardenpho process, with Enhanced Biological Phosphorus Removal (EBPR).

The incorporation of a bioreactor configuration with EBPR is not only beneficial to achieving the low TP concentrations required within the final effluent, but also reduces the amount of supplementary phosphorus removal chemicals required during the lifetime of the STP.

Similarly the incorporation of membrane ultra-filtration improves the quality of the released permeate by limiting the carryover of phosphorus containing biomass into the permeate stream, assisting in achieving the low TP effluent concentrations required. This complex process required significant automation, including monitoring to ensure the treated effluent meets the requirements.

A key innovative feature of the STP is the increased water depth of the bioreactor. The increased bioreactor depth allows improved nutrient performance via the buffering of influent hydraulic and nutrient loads, which is performed by varying the effluent production rate of the MBR system, ultimately varying the height of liquid within the bioreactor. This allows for greater retention time within the bioreactor which enhances biological treatment performance.

Dean Bryant (R) NSW Sales Manager at Burkert Fluid Control Systems congratulates winners Damian Sharland of SKM and Peter Bailey (L) of Queensland Urban Utilities.

Dean Bryant (R) NSW Sales Manager at Bürkert Fluid Control Systems congratulates winners Damian Sharland of SKM and Peter Bailey (L) of Queensland Urban Utilities.

Although the main benefit of the increased bioreactor depth is improved biological nutrient removal performance, this functionality also provides potential power consumption efficiencies by allowing hydraulic loads to be buffered during peak power consumption periods, and allowing increased permeate production by the MBR system during off-peak periods.

Utilisation of the flow balancing available within the bioreactor of the STP minimises power consumption in addition to assisting with the plant meeting compliance during peak loading at final design loading conditions. Another significant challenge for the design of the Goodna STP was the constrained land availability and the existing operating STP on the site, which contained a large amount of infrastructure.

This resulted in the need for a very compact site layout for the upgraded plant, with existing structures used heavily during the upgrade. The existing Stage 3 Modified Ludzak-Ettinger MLE configuration bioreactor was converted into a MLE configuration aerobic digester to provide stabilisation of the biosolids from the upgraded STP, which provides increased dewatering capability of the biosolids and reduces the overall biosolids production from the upgraded STP.

The existing dewatering facility, incorporating Gravity Drainage Decks, Belt Filter Presses and polymer batching units was also retained to minimise the amount of redundant infrastructure onsite. The existing final clarifier from the Stage 3 system was also retained and refurbished to provide emergency clarification during mixed liquor bypass from the MBR system. This continuation of operation requirement, whilst modifying the existing works, required extensive planning regarding the automation cut-overs.

A number of energy efficiency measures were included in the design, including utilisation of load/unload control regimes for the bioreactor and MBR blowers systems, on/off control regimes for the digester blowers, digester mixers and bioreactor mixers, and high efficiency aeration diffusers within the bioreactor.

The Goodna STP incorporates real time monitoring and control of processes throughout the STP, specifically via the inclusion of analysers in all process streams to assess the real time performance of nutrients such as ammonia, nitrate and orthophosphate, with all monitoring conducted via a completely new SCADA system for the STP.

This increased monitoring and process control, monitors nutrient reduction performance as expected, however in addition it also suggests automatic control actions to assist operators with maintaining nutrient performance within the desired range or alternately to reduce chemical consumption during periods of low influent load or excellent performance.

This is conducted through the implementation of optimised chemical dosing or aeration control, which is achieved through feedback from the associated analysers, such as alum trimming based on permeate orthophosphate concentrations, methanol trimming based on nitrate concentration and aeration trimming based on ammonia concentrations within the bioreactor.

Performance of the Goodna STP during the final commissioning and proving operations has been exceptional with median nutrient concentration in the effluent of 1.9 mg/L and 0.8 mg/L for TN and TP respectively. The implementation of a sophisticated real time monitoring and control system as part of the Goodna STP upgrade is a critical element in the achievement of promoting a healthy ecosystem that will sustainably support the livelihoods and lifestyles of people in the region.

Although a number of challenges were posed during the design of the upgraded Goodna STP, the use, control and monitoring of innovative design features have combined to deliver a limit of technology process that is achieving exception effluent nutrient performance.

Project: The Nepean Water Filtration Plant – Electrical and SCADA Upgrade

One of Sydney Water’s critical water supply systems is the Nepean Water Filtration Plant (WFP), located in the Southern Highlands of NSW, supplying residents with 36 million litres of water a day. Water filtration plants receive raw water from dams and treat it to drinking water quality before supplying homes. Drinking water is tested at every stage of the process ensuring the water is of excellent quality, and meets the Australian Drinking Water Guidelines.

The Nepean WFP in the Southern Highlands of NSW draws raw water from the Nepean Dam, supplying the townships of Bargo, Couridjah, Buxton, Thirlmere, Tahmoor, Picton and adjacent areas. Built in 1976 with a capacity of 22 ML/d, the WFP was upgraded in capacity to 36 ML/d in 1991.

The PLC & SCADA system at Nepean WFP installed during the upgrade in 1991 was nearing obsolescence and becoming increasingly difficult to support. The system was unreliable, and was not scalable. The communication network was unstable, and SCADA screen updates were slow. To improve the reliability of the plant, UGL was engaged to implement a new site wide PLC & SCADA system, alongside mechanical and electrical equipment upgrades.

UGL’s rigorous adherence to quality procedures ensured that any project design changes were identified and implemented early during the development stage of the control system design. This structured approach greatly reduced problems and re-work during the commissioning and cut-over periods of the upgrade.

UGL connected Siemens’ Simocode Smart Starters, Variable Speed Drives (VSD), Sipos Motorised Positioning Valve actuators and Power Monitors to the Profibus communication network. This ensured a standard approach to equipment selection and communication protocol across the plant.

Over 65 motorised positioning valve actuators were connected to the Profibus network. To prevent the risk of flooding in the event of a plant wide power or Profibus failure, these actuators needed to be engineered to move to a ‘Failsafe’ position in these conditions.

However, the actuator at the time did not have a Profibus related trigger function programmed in its firmware. UGL worked closely with the actuator’s software designers in Germany to update the actuator’s firmware to provide this function.

Additionally, the plant UPS was not sized to allow all 65 actuators to move at once. UGL overcame the problem by incorporating an adjustable time delay into the actuator’s software, allowing sequential initiation of the actuator movement, averting an overload of the UPS during power failure.

A significant project challenge was to ensure that this complex brown-field site maintained operation and continuity of water supply at all times. This was especially demanding when only parts of the plant were being converted to the new control system, with other parts remaining operational in the legacy system.

Consideration had to be given to interlock conditions of process sequences in old and new PLC & SCADA software, with the plant as a whole continuing to operate in automatic control. With the lack of a common communication protocol between the new and legacy control systems, a gateway was installed as a communication interface between the two systems.

The control system team then designed and programmed Temporary Operating Modes (TOM) to make sure that all processes operated successfully while cut-overs were taking place.

Recalibrating existing and installing additional online instrumentation improved the monitoring abilities of the raw water qualities pumped from the Nepean Dam. Superior control system functionalities developed as part of the project means operators now efficiently deal with sudden changes in the process.

This is especially beneficial after heavy rainfalls, which has effects on the raw water pumped into the plant. Variations in the raw water quality are detected much earlier and operators are able to easily adjust plant parameters.

Burkert sponsors the 2013 PACE Zenith AwardsThe 2013 PACE Zenith Water & Wastewater Awards are sponsored by Bürkert Fluid Control Systems.
ürkert Fluid Control Systems
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