EFFLUENT REUSE AT EAST LISMORE WASTEWATER TREATMENT WORKS

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1 EFFLUENT REUSE AT EAST LISMORE WASTEWATER TREATMENT WORKS Jeremy Silk Project Engineer, Lismore Water, NSW Janaka Weeraratne A/Manager, Lismore Water, NSW Summary The East Lismore Wastewater Treatment Works uses approximately 50 ML of potable water per year for cleaning purposes, making it one of the highest water users within Lismore City Council. The majority of this water is used on two large industrial plant items within the treatment works, for the sole purpose of cleaning filters. Lismore City Council staff designed and constructed a reuse system, with the aim of making initial savings of 40 ML of potable water per year. The project highlights that in many instances, water of drinking quality standard is often not required for industrial processes. Introduction Lismore Water, a business unit of Lismore City Council, is actively involved in better managing the water and wastewater cycles. As part of this effort, Lismore Water has implemented a water reclamation and reuse project at the East Lismore Wastewater Treatment Works. The treatment works currently treats 5.1 ML of sewage per day, servicing approximately 22,000 people. As an initial step, Lismore Water decided to reuse this water to replace the potable water on two items of plant within the treatment works. The two items are the gravity drainage deck (GDD) and belt press filter (BPF), which currently use approximately 80% of the consumed 50 ML of potable water. In future, it is expected that this reclaimed water will also replace some of the potable water used at Tryton s Vermiculture Plant (worm farm) which is located adjacent to the treatment works. The worm farm is the largest of its kind in the Southern Hemisphere. The reuse of reclaimed water will initially save 40 ML per year of potable water ($40,000 per annum) and these saving would increase as the reclaimed water is further used in other locations. This also reduces the effluent discharged into Monaltrie Creek, which eventually flows out into the Wilsons River. Background In 1879, Lismore was proclaimed a municipality and in the following years, there were reports of drainage problems with runoff containing raw sewage. On 16 th May 1901, Lismore was gazetted a sewerage district and in 1906, the first sewerage works were completed. In 1954, Lismore s second treatment works was completed and this is now known as the East Lismore Wastewater Treatment Works. In 1998, an upgrade of this treatment works was undertaken which converted the existing trickling filter plant into a state of the art biological nutrient removal (BNR) sewage treatment plant capable of treating 30,500 EP. These works included the laying of effluent reuse pipework parallel to the potable water supply, which was the foundation of the 2005 effluent reuse project. Effluent Reuse at East Lismore Wastewater Treatment Works 1 of 9

2 In 2003 additional augmentation works were undertaken, resulting in the construction of an ultra violet (UV) disinfection system that is capable of disinfecting up to 250 L/s of treated effluent. This unit consists of two banks of lamps with each bank having 32 UV lamps. Project Planning and Development Initially this project was to be incorporated into the design and construction of the UV disinfection facility. The idea was to reuse effluent on two existing high uses of water within the treatment works, namely the: 1. Belt press filter (BPF); and 2. Gravity drainage deck (GDD) The main function of each item of equipment is to dewater the sewage sludge at different stages of the treatment process. Both items previously used potable water (approximately 110 kl/day) to spray clean tensioned conveyor belts and prevent them from clogging. Consideration was also given to the potential of using reclaimed water at various hose cocks around the treatment works. Further investigation of the initial proposal discovered several flaws in the design of the reuse system, the main one being a lack of storage for the reclaimed water. The original requirement for a 4,000L storage facility at the end of the UV channel was insufficient as it relied on constant flow through the UV disinfection channel. It was soon discovered that constant flow could not be guaranteed. Because of these flaws, it was decided to remove the effluent reuse component from the UV contract and complete it once the UV disinfection facility was completed and fully operational. Hence the reuse component was designed and constructed by Council staff. With Council now taking full responsibility for the project, a number of objectives were developed by which the success of the project could be gauged. The objectives are listed below. To replace potable water used within the treatment works with UV disinfected reclaimed water. This would initially save 40 ML of potable water a year ($40,000 per annum) and reduce potable water consumption by approximately 80%. Improve knowledge and skills within Council and use them to determine what can be achieved with reclaimed water and to transfer those lessons learnt to future reuse projects. Show leadership by innovation in better managing the water and wastewater cycles, as highlighted in Lismore City Council s Strategic Plan. Design and construct a reuse system that is expandable for potential future users of the reclaimed water, particularly Tryton s Vermiculture Plant located adjacent to the treatment works. Processes The initial plan to supply the reuse main from the UV channel was to involve the installation of a pressure pump at the,4000l storage facility and connect it to the reuse main which was laid in However, owing to the lack of storage and a lack of recognition of the water quality requirements of the GDD and BPF, the initial cost estimate was revised to incorporate the additional infrastructure. Benefits with constructing the system with the additional storage are that future expansion to the worm farm will require fewer modifications. The transfer of tertiary treated reclaimed water to the GDD and BPF is as follows: 1. Reclaimed water is pumped from the 4,000L holding tank at the end of the UV disinfection channel. The lift pump is capable of pumping 15 l/s at 15m head. 2. The reclaimed water then passes through a gravel filter system that has been designed according to the water quality requirements of the GDD and BPF. This includes a requirement that the suspended solids in the reclaimed water do not exceed 30 ppm and that Effluent Reuse at East Lismore Wastewater Treatment Works 2 of 9

3 particles are less than 0.5mm in diameter. 3. The effluent is then stored in the two 34,000L rainwater tanks. 4. Downstream of the holding tanks is a pressure pump system, which is used to pressurise the reuse main to 800 kpa. The transfer process is shown schematically in Appendix A. Duration and Cost of Project July 2005 October 2005 at a total cost of $105,000. Environmental Issues One of the greatest benefits produced by undertaking these works has been to the environment. The reduction in water consumption within the Lismore region delays the need for future expansion of the water source and the discharge from the treatment works to Monaltrie Creek is reduced. The end result is that what was once considered a waste (effluent) is now considered to be a resource (reclaimed water). The reduction in water consumption is shown in the graph below (Figure 1). This graph highlights that daily water consumption at the treatment works has decreased from kl per day to 50 kl per day as a result of the commissioning of the reuse system. East Lismore Treatment Works Water Consumption Daily Water Consumption (kl) Reuse Commissioned Dec-04 Mar-05 Jun-05 Sep-05 Dec-05 Date Figure 1. Daily Water Consumption at the East Lismore Wastewater Treatment Works At the moment there is no firm indication that the electricity consumption has gone up since the commissioning of the reuse system. The implementation of the reuse system involved the installation of extra pumps; the lift pumps from the end of the UV disinfection channel and the pressure pump system downstream from the storage tanks. However, the decommissioning of four washwater booster pumps at the GDD and BPF has offset the expected electricity consumption increase. The graph below (Figure 2) shows the electricity consumption for the last few years. Effluent Reuse at East Lismore Wastewater Treatment Works 3 of 9

4 East Lismore Wastewater Treatment Works Electricity Consumption 140,000 Electricity Consumption (kwh) 135, , , , , , ,000 UV Commissioned Reuse Commissioned 100,000 Jan-03 Apr-03 Jul-03 Oct-03 Jan-04 Apr-04 Jul-04 Oct-04 Jan-05 Apr-05 Jul-05 Oct-05 Jan-06 Date Figure 2. Electricity Consumption at East Lismore Wastewater Treatment Works Conclusion This project highlights that in many instances, water of drinking water standard is often not required for industrial processes. The methodology used for this project could also be employed in other industrial processes, using rainwater where reclaimed effluent is not available. Due to the nature of wastewater treatment works having similar designs, it is likely that there are many throughout NSW and Australia that are high potable water users such as East Lismore. A reuse project such as the project that Lismore Water has undertaken is a feasible option for all these facilities and if implemented, would save a considerable amount of potable water. By investigating and implementing an effluent reuse scheme, this project also highlights the environmental and economic benefits that can be achieved by Local Government. In this instance, the environmental benefit gained by decreasing the potable water consumption has a flow on economic benefit, resulting in a saving of approximately $40,000 per annum to Council and allows the bulk water supplier to delay any future expansion of the potable water source. Effluent Reuse at East Lismore Wastewater Treatment Works 4 of 9

5 Appendix A Figure 3. Effluent reuse schematic Effluent Reuse at East Lismore Wastewater Treatment Works 5 of 9

6 Appendix B - Photos Figure 4. Suction pump at the end of the UV channel Figure 5. Gravel filter Effluent Reuse at East Lismore Wastewater Treatment Works 6 of 9

7 Figure 6. Reclaimed water storage Figure 7. GDD belts being cleaned Effluent Reuse at East Lismore Wastewater Treatment Works 7 of 9

8 Figure 8. Belt Press Filter Effluent Reuse at East Lismore Wastewater Treatment Works 8 of 9

9 Author Biography Jeremy Silk graduated from the University of Newcastle in 1997 with a Bachelor of Environmental Engineering. He has worked for Lismore City Council for three years, after working in the sewer flow monitoring industry with ADS Environmental Services for over 4 years. Since working with Lismore City Council he has undertaken various projects, including managing the construction of a 7 ML leachate pond and the East Lismore Wastewater Treatment Works effluent reuse scheme. Additional projects include supervision of the UV disinfection scheme at East Lismore Wastewater Treatment Works and the management of projects related to the inflow/infiltration of stormwater into the sewer system. Postal Address: Lismore City Council, PO Box 23A, Lismore, NSW Address: jeremy.silk@lismore.nsw.gov.au Telephone: (02) Fax: (02) Janaka Weeraratne graduated from the New South Wales University in 1986 with an honours degree in Civil Engineering. Since graduating from University, Janaka initially worked with the Department of Public Works, NSW where Janaka was involved in numerous water supply and wastewater schemes from supplying improved water supply to communities such as Lightning Ridge and White Cliffs to wastewater supply schemes to communities such as Baradine and Nyngan. While in Lismore, Janaka has been involved in various water and wastewater schemes from upgrading of pump stations, design of new water and sewer reticulation systems, community consultation for the Nimbin Water Supply to the upgrade of the telemetry system. Postal Address: Lismore City Council, PO Box 23A, Lismore, NSW Address: janaka.weeraratne@lismore.nsw.gov.au Telephone: (02) Fax: (02) Effluent Reuse at East Lismore Wastewater Treatment Works 9 of 9

6 WASTEWATER. 6.1 Overview. 6.2 Darvill Wastewater Works

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