Irrigation futures a framework for efficient wastewater treatment and recycling systems


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A framework for efficient wastewater treatment and recycling systems -

Gayathri Devi Mekala, Brian Davidson, Madar Samad and Anne-Maree Boland. Irrigation Australia Journal, Spring 2008.

The drought conditions of the past seven years in Australia and increasing environmental
awareness have led to an active promotion of wastewater recycling. The absolute and relative cost of recycling is one of the key factors that will have a big influence on the
future of wastewater recycling in Australia.

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Irrigation futures a framework for efficient wastewater treatment and recycling systems

  1. 1. A FRAMEWORK FOR EFFICIENT WASTEWATER TREATMENT AND RECYCLING SYSTEMS Gayathri Devi Mekala, Brian Davidson, Madar Samad and Anne-Maree Boland The drought conditions of the past seven years in Australia and increasing environmental awareness have led to an active promotion of wastewater recycling. The absolute and relative cost of recycling is one of the key factors that will have a big influence on the future of wastewater recycling in Australia. This article outlines the development of a toolkit/decision support tool for allocating wastewater among different sectors to achieve desired objectives in a cost-efficient way. It deals in particular with answering these questions: • How can the cost-effectiveness of wastewater recycling be judged and budget allocated? • For which sectors in a defined region will wastewater recycling be cost-efficient? A Broccoli field in Werribee Irrigation District irrigated with treated wastewater. The vegetables Wastewater has a number of most commonly irrigated with recycled wastewater from the Western Treatment Plant in the alternative uses and each alternative Werribee Irrigation District are broccoli, cauliflower, cabbage, onion, artichoke and lettuce. is associated with a set of costs from the point of treatment to the point of use. As a result, recycling can satisfy prove to be the basis of a decision nothing). Only if the new strategy is more than one objective such as: support tool that can be used to associated with enhanced effects and reduce the discharge of nutrients to allocate wastewater among different higher costs, is cost-effectiveness natural water bodies, save/substitute sectors. analysis required. It is compared potable water, bring more land under against current practice (the “low-cost cultivation, and save water for Cost-effectiveness analysis alternative”) in the calculation of the environmental purposes. The Cost-effectiveness analysis (CEA) is incremental CE ratio: methodology chosen to evaluate the one of the techniques for economic best alternative or alternatives is evaluation in which all costs are Cost-Effectiveness Analysis. related to a single common effect. It The cost effectiveness of a particular is designed to compare the cost The result might be considered as alternative depends on what one effectiveness of an intervention and the “price” of the additional outcome wants to achieve. Therefore, a ranking determine if the intervention is worth purchased by switching from the exercise needs to be conducted for the doing. It is a technique for selecting among competing wants wherever current practice to the new strategy. different objectives among stakeholders and each objective resources are limited. It was first The choice of technique depends weighted accordingly. A further step applied to health care in the late on the nature of the benefits may be comparing the cost- 1970s to make decisions on specified. In CEA, the benefits are effectiveness of wastewater recycling appropriate strategies to increase expressed in non-monetary terms and with other options like buying water health benefits or cost savings. in cost-benefit analysis they are on the market from the agricultural In cost-effectiveness analysis, a new expressed in monetary terms. As with sector and desalination. It is hoped strategy is compared with the current all economic evaluation techniques, that the approach outlined above may practice (which may include doing the aim of CEA is to maximise the32 IRRIGATION AUSTRALIA
  2. 2. CRCIFlevel of benefits relative to theresources available. With CEA, it is normal todistinguish between the direct costsand the indirect costs associated withthe intervention, together withintangible positive and negativeexternalities, which although at timesdifficult to quantify, are oftenconsequences of the intervention andshould be included in the cost profile.The costs to be considered for CEA ofrecycling projects are:• direct costs: includes capital costs of treatment and distribution of recycled water• indirect costs: e.g. groundwater pollution of areas irrigated with recycled water• intangibles: includes “yuck” factor, non-acceptability of the wastewater irrigated products. It is important to specify the costs to Werribee Park Tourism Precinct: All these five public areas now use recycled water forbe included in a CEA and those which irrigation from Western Treatment Plant.should not to reduce the risk ofmisinterpreting the findings. Adistinction must be made between which by definition are uncertain, the recycling infrastructure only if theythose interventions that are level of confidence that can be placed are financially viable and it is worthcompletely independent, i.e. where in them need to be identified. In a the risk. Therefore, the cost ofthe costs and effects of one dynamic market, both the costs and supplying recycled water becomes aintervention are not affected by the the effects can change. Sensitivity crucial determinant of overall projectintroduction or otherwise of other analysis tests all assumptions used in viability. It is important to recogniseinterventions, and those that are the model and enables the impact of that the direct costs of providingmutually exclusive, i.e. where the best-case and worse-case settings recycled water will depend on theimplementing one intervention means on the baseline findings to be specific nature of the project and thethat another cannot be implemented, investigated. use to which the recycled water will be put.or where the implementation of oneintervention results in changes to the Procedure for conducting the ACIL Tasman broadly categorisedcosts and effects of another. cost-effectiveness analysis the infrastructure related costs The four sectors where wastewater can associated with recycling as: For the current study, wastewater be recycled and for which the CEA can • capital costs for new or upgradingrecycling was considered to be an be conducted are: treatment plants, and subsequentindependent programme. Using CEA • household/residential operating costswith independent programmes • industry • installing and operatingrequires that cost-effectiveness ratios • recreational irrigation reticulation and trunk delivery(CERs) are calculated for each • agriculture. systemsprogramme and ranked. • storage capacity where needed to The cost-effectiveness of using match seasonal variations in recycled water for each of the sectors production and demand is obtained by summing the costs of Interventions with the least CER • costs incurred by users in using recycled water for each of theshould be given priority but to decide accessing recycled water, e.g. options (which includes the cost ofwhich programme to implement, the converting equipment, plumbing, treatment to comply with the EPAextent of resources available must be and extra on-site storage or standards for each of the specific usesconsidered. In mutually exclusive treatment. and to take it to the point for use) andinterventions, incremental cost- Other costs of supply include: dividing this cost by the intendedeffectiveness ratios (ICERs) are used: • project planning and regulatory impact it creates depending upon the approvals objective one chooses to attain. • marketing, public education and Costs to be included for CEA. In consultation programs Alternative interventions are ranked 2005 ACIL Tasman Pty Ltd conducted • capital and operating costs of anyaccording to their effectiveness on the stakeholder consultations to identify additional treatment and waste-basis of securing maximum effect the impediments to recycling. stream treatment followingrather than considering cost, and Seventy-seven per cent of stakeholders recycled water useICERs are calculated. identified the cost of infrastructure as • ongoing monitoring and The results of CEA should be an important impediment to the compliance with regulatorysubjected to a sensitivity analysis. supply side of the recycled water requirements and other riskSince the CERs are point estimates, market. Water companies can invest in management measures IRRIGATION AUSTRALIA 33
  3. 3. CRCIF • contingent liabilities for possible Table. Possible objectives of recycling and the expected effect. legal claims arising from inappropriate use of the recycled Objective Criteria for Effectiveness (AUD*/effect) water • metering, billing, and other To reduce the nitrogen load released AUD/tons of nitrogen discharge customer-related costs. into the bay/river reduced into bay/river The capital and operating costs of To save potable water or create AUD/gallons (GL) of potable water treating wastewater to a standard alternative or new sources of water saved suitable for its intended use will to complement the existing sources depend on factors such as the quality To reduce the costs of treatment by AUD/kilolitres of wastewater treated of the effluent, the quality of the treating the water to a lower level recycled water required, the technology adopted or required for To promote regional development in AUD/number of people employed the appropriate level of treatment, new areas through employment and the extent of economies of scale. generation and promotion of primary The general position is that the industries higher the level of treatment, the * Australian dollars higher the cost. The relative cost- effectiveness of recycled water schemes in terms of cost per environment, and inadequate acceptability of using recycled water megalitre varies a lot from project to community consultation on the is higher for non-edible crops than project, with a high volume of issue. for edible crops. For edible crops, industrial or agricultural schemes 2. Lack of trust in technology: in a preference is towards crops that must benefiting from economies of scale. 1999 study by Sydney Water, the lack be peeled or washed before human A common issue raised by suppliers of trust in technology was the second consumption like oranges and consulted in this research was the most frequently stated reason given sweetcorn. challenge and costs associated with by participants who opposed using However, a 1988 study using overcoming the spatial separation of reclaimed water for agricultural salient options, which specifically supply. irrigation. described how and when the recycled Objectives of wastewater 3. Social pressure and fear of social water was to be used in a recycling. State governments have a backlash: a heightened need for new community, found that the degree of variety of objectives for recycling. water sources does not automatically contact was not related to how Depending on the objective, the warrant the acceptability of acceptable people perceived a certain results of the CEA will vary. The wastewater recycling. Drought- use option to be. Rather participants different possible objectives are affected Werribee farmers were favoured specific-use options which shown in the table. offered a deal to access water from conserved water, enhanced health the Thompson Dam by the Victorian and reduced treatment and Depending on the objective (see Government in 2004, in return for distribution costs. After all the the table) that an institution/ which they were required to sign up factors that influenced overall public community wants to achieve, the to a program to take reclaimed water perceptions of use were collated as sector to which the recycled water is the following year. Only half of the (1) degree of human contact and (2) allocated would vary and so would farmers have so far accepted the deal. the five factors (i.e., health, the costs and its effectiveness. It is environment, treatment, distribution also possible that governments and Others are reluctant because of fears and conservation) it was concluded communities will have a number of of possible community backlash. that the first component only had a objectives that they want to achieve 4. Fear of losing markets: the greatest greater effect when people were through recycling. In such instances, concern for growers is maintenance asked about general use options, there is a need to weight and rank of markets, i.e. continued access and whereas when the specific use the different objectives based on assured price. A recent survey by the scheme was used, the second their perceived importance. Department of Primary Industries component had greater impact on asked consumers if they would be Weighting objectives of people’s perceptions. willing to buy vegetables grown in recycling Therefore, it is essential to weigh Werribee with recycled water. The the different objectives of the The options for wastewater recycling results were as follows: government for recycling options in are varied and contentious because of • Yes - 35% - Support the use of coordination with user and consumer its nature of origin and issues and recycled water; trust the acceptability and preference and perceptions related to health and authorities to do the right thing accordingly select the recycling safety. The local communities have • Not sure - 55% - If the water is projects which are most likely to be rejected a number of wastewater treated properly; if safety is accepted by the community and recycling projects by the government guaranteed therefore make the project and water boards around the world • No - 10% - Don’t like the idea of implementation successful. The and in Australia. A number of social using recycled water different weighting methods include reasons have been found to be Literature review and previous equal weighting of all attributes, rank associated with the rejection: studies have consistently shown that order weighting and ratio weighting. 1. Lack of coordination between the the closer one moved on the contact In a 1993 simulation study it was authorities involved in planning continuum, the less acceptable the health, water supply and recycling option became. The Continued over page34 IRRIGATION AUSTRALIA
  4. 4. IRRIGATION RESEARCHIRRIGATION RESEARCHRECYCLED WATER SAVING VITICULTUREBelinda Rawnsley, Senior Research Officer, South Australian Research & Development InstituteRecycled water is droughtproofing Comparison of selected quality parameters of recycled and mains water used to irrigateMcLaren Vale, keeping it one step vines in McLaren Vale, South Australia.ahead of other regions affected bywater shortages. Parameter Unit Recycled Mains The use of recycled water in the pH 7.4 7.4McLaren Vale region has observablebenefits by alleviating pressure on Boron mg/L 0.23 0.33naturally available water resources and Calcium mg/L 42 41is up to 40% cheaper per kilolitre thanmains water. Environmentally, the Chloride mg/L 270 138amount of wastewater discharged out Potassium mg/L 25 7to sea is reduced which minimises theharmful impact on the marine Sodium mg/L 190 88environment in the Gulf St Vincent. Total Nitrogen mg/L 20 0.3 Recycled water quality is constantly Total Phosphorus mg/L 8 0.08monitored. Compared to mains water,recycled water tends to have a higher Total Dissolved Solids (TDS) mg/L 807 373salt content and nutrient load (see E. coli /100ml 18 0table). Nitrogen (N) and phosphorus(P) are higher in recycled water than Source: Christies Beach Wastewater Treatment Plant and Myponga system, SA Water 2006.mains water so additional fertiliser usemay not be necessary. There arecommon concerns that recycled watercontains excessive levels of boron, yet between vines irrigated with recycled nutrients that can reduce growerthere is no evidence of this (see table). or mains water. This research has fertiliser costs. The use of recycled water has many shown that irrigation with recycled I also have conducted research onobvious benefits and ongoing water does not cause nutrient the effect of recycled water on the soilresearch, led by Dr Michael McCarthy imbalance and does not impede yield. environment, particularly the level of(SARDI), has shown that there is no Recycled water appears to provide a microbes in the soil and whether soildifference in yield or wine quality good source of plant available pathogens pose a problem. Continued from previous page Bruvold, W. 1988. Public opinion on pp. 1-6. http://www.evidence-based- water use options. Journal WPCF 60(1): found that ratio weights and rank 45-49. order weights were much superior to PMSEIC (Prime Minister’s Science, D’Angelo Report. 1998. See Using Engineering and Innovation Council). the equal weights method. Reclaimed Water to Augment Potable 2003. Recycling Water for Our Cities. Water Resources. Public Information References Paper prepared by an independent Outreach Programs (Special Publication, ABC online. 2004. Werribee farmers get working group for PMSEIC. 28 Salvatore D’Angelo, Chairperson). government water deal. News retrieved November 2003, pp. 1-45. Publishers: Water Environment January 9, 2004 Federation & American Waterworks Sydney Water. 1999. Community views on ACIL Tasman Pty Ltd. 2005. Economics Association. recycled water. Sydney. Policy Strategy. Research into access to Eddy. D. M. 2000. Effective Clinical recycled water and impediments to recycled water investment. Report Practice. Journal of American Medical About the authors Association 3(5): 253-255. Gayathri Devi Mekala works with prepared for the Australian Government Department of Jia, J.; Fischer, G. W.; Dyer, J. S. 1993. the CRCIF, University of Melbourne Agriculture, Fisheries and Forestry on Attribute Weighting Methods and and International Water behalf of the Natural Resource Policy Decision Quality in the Presence of Management Institute, Brian and Programs Committee. June 2005, Response Error: A Simulation Study. Davidson with the CRCIF and pp 1-82. Journal of Behavioral Decision Making. May 1993. University of Melbourne, Madar Boland, A. 2005. The use of recycled water Phillips, C.; Thompson, G. 2001. What is Samad with the International Water in Australian horticulture Keynote address at Irrigation 2005 – Irrigation cost-effectiveness? Published by Management Institute, and Anne- Association of Australia Conference, Hayward Medical Communications. Maree Boland with RM Consulting Townsville. Aventis House. Volume 1, Number 3. Group. IRRIGATION AUSTRALIA 35