Phosphorus, Quality and Energy: Challenges for the Wastewater Industry Presenting Author Amanda J Lake 1

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1 Phosphorus, Quality and Energy: Challenges for the Wastewater Industry Presenting Author Amanda J Lake 1 1 Jacobs Engineering, Edinburgh, Scotland, UK Short Abstract At a time when the global community seeks to combat climate change through lower energy technologies and reduced natural resources consumption, improvements demanded in the quality of wastewater discharged to the environment necessitate ever increasing energy inputs. With a focus on phosphorus removal, this paper provides an overview of the wastewater treatment quality-energy nexus and a summary of the current policy frameworks applicable to phosphorus and water quality in Europe with a focus on the UK and Scotland. Key opportunities exist for participation by the wastewater industry in achieving water quality objectives and emissions reduction. This will require improved participation and communication by an industry focused on engineering end of pipe solutions. Keywords: Energy, Phosphorus, Wastewater, Water Framework Directive Introduction Phosphorus is vital for human and plant life and has helped transform our society through modern agriculture. Most recently, focus has been on its negative impacts in eutrophication of water bodies and the European Union (EU) has enacted legislation to combat this at a catchment level via the Water Framework Directive (WFD). The UK Water Industry has predicted an increase in greenhouse gas emissions of up to ninety percent if water quality objectives under the WFD are to be achieved - primarily due to increased energy usage, chemical usage and sludge production. Yet, in order to meet challenging emissions targets, the industry must substantially reduce its carbon emissions. This paper provides an overview of the origins and fate of phosphorus against the background of the WFD approach with a focus on the UK and Scotland. Its purpose is to provide a policy background and to challenge the reader and water industry practitioners to appreciate wider issues. Phosphorus origins Historically, phosphorus required for animal and plant growth was available in soil structures and returned to these in the application of human and animal wastes. Modern day agriculture has broken this cycle and requires mining of phosphate rock for production of fertilisers. Forty percent of the world s phosphate rock resources lie in Morocco and Western Sahara; China has the second largest reserves (U.S. Geological Survey, 2011). Resoures are limited and the potential for peak phosphorus is increasingly recognised (Vaccari, 2009; Soil Association, 2010). Phosphorus use by humans is primarily in fertilizers and household detergents. UK domestic inputs by mass are illustrated in Fig. 1. Page 1 of 8

2 Water treatment chemicals 5% Dishwashing detergents 7% Laundry detergents 18% Other 6% Urine 32% concentrations can lead to eutrophication - the enrichment of water bodies by nutrients causing an accelerated growth of algae and higher forms of plant life which causes undesirable disturbances and which can result in loss of aquatic life (OJ L, 1991). Faeces 32% Fig. 1: Domestic phosphorus inputs by mass (Source: UKWIR, 2009 Point source human phosphorus inputs may comprise some fifty percent of total inputs to EU water bodies the remainder is diffuse though apportionment between sources is highly catchment specific (EEA, 2005). Food related phosphorus intake, primarily through meat and dairy products, is estimated at 1244 mg/d per person (Food Standards Agency, 2003). Nutritional phosphorus requirements are estimated at 550mg/day (British Nutrition Foundation, 2009). As food additives 1 phosphorus compounds are increasingly added to improve functionality in restructured meats, processed cheeses, instant and refrigerated bakery products (Jones, 2009; Uribarri & Calvo, 2003). Phosphorus and Water Quality Phosphorus from fertilizer or slurries in excess of plant nutrient needs runs off with soil into watercourses following rainfall. Septic tanks and sewage treatment facilities also discharge point source phosphorus in effluents. Resulting elevated phosphorus The EU legislative response The issue of eutrophication from phosphorus is addressed by EU Member Countries through various legislative controls. 1. Source Reduction While a number of member states had already banned phosphates in laundry detergents 2, the European Commission (EC) has recently proposed a ban on phosphates in laundry detergents from 2013 (EC, 2010). In the UK phosphate containing detergents have a seventeen percent market share and while consultation for their phase out is ongoing it seems unlikely to bring any imminent result. Neither the EC ban nor UK proposals concern dishwashing detergents which include dishwasher tablets and comprise an estimated seven percent of phosphorus in domestic sewage with dishwasher use also predicted to increase (UKWIR, 2009). Although increasing attention is being given to dietary phosphorus intake, evidence suggests this will further increase due to increasing consumption of meat and fast foods (Uribarri & Calvo, 2003). 2. Diffuse Pollution from Agriculture EU member states have instigated various mechanisms for control of diffuse pollution from agriculture under the Water Framework 1 With some sixteen phosphorus containing E numbers to be counted at 2 EU Member States Belgium, Germany, Ireland, Italy, Luxemburg, Netherlands and Austria have all banned phosphates in laundry detergents. Page 2 of 8

3 Directive (discussed subsequently) and in response to agricultural and water source protection legislation. Within Scotland, General Binding Rules have been developed under the Water Environment (Diffuse Pollution) (Scotland) Regulations 2008 and cover activities which may result in diffuse pollution including agriculture. The Scottish Environmental Protection Agency (SEPA) has proposed a two tier approach for enforcement - a national awareness campaign and identification of priority sub-catchments. SEPA are presently 3 assessing the extent of diffuse pollution through measures such as on-theground river walks but it is clear that diffuse pollution identification and management - despite likely to be contributing significant phosphorus loads - is in its formative stages in Scotland. 3. Point Source Inputs from Sewage End of pipe phosphorus reduction is achieved through the Urban Wastewater Treatment Directive (1991/271/EEC). This sets nutrient limits on STW discharges for works greater than 10,000 population equivalent 4 (PE) discharging into sensitive areas subject to eutrophication - requiring a 2mgP/l total phosphorus concentration on an annual average basis or a minimum eighty percent reduction in incoming load. For STWs of greater than 100,000 PE, a 1mgP/l limit is applied (OJ L, 1991). 3 See /perthshire-s-waterways-under-scrutiny-fromsepa.html - though one to one discussions with landowners found to be in breach of general binding rules on diffuse pollution have been delayed in this catchment until late With one PE equivalent to 60g BOD per person per in day raw sewage in UK design standards. Since the Directive s introduction in 1991, UK Water Companies have implemented significant reduction of phosphorus loads; effluent phosphorus discharges to the Thames have reduced almost ten fold in the last twenty years (Neal et al., 2010). 4. WFD A River Basin Approach The Water Framework Directive (2000/60/EC), introduced in 2000, is considered the most significant international water legislative instrument to be introduced to date. It establishes a framework for the protection and improvement of water bodies, promoting sustainable use and protective management measures and is novel in its requirement for economic analysis of water and for full public participation in the development of river basin management plans (OJ L, 2000). Member countries are required by 2015, through river basin planning, to achieve good 5 status in all surface water bodies unless this is disproportionately expensive 6. Perhaps the most important concept of the WFD for the water industry is that, following data gathering and assessment, it requires the prioritisation of key measures to address pressures such as eutrophication on water quality status at a river basin and subcatchment level and it requires stakeholder participation. While there is evidence that regulators are developing the means to apportion and 5 Good being defined for ecological and chemical status of the water body see WFD Article 2. 6 There is plenty of UK discussion concerning disproportionate costs in the WFD but no examples of determining this in practice. See Proceedings of the 4th European Water and Wastewater Management Conference, edited by Horan, N.J. Aqua Enviro, September Page 3 of 8

4 assess the relative contribution of phosphorus from point and diffuse catchment sources, this process is in its formative stages and a significant impact of the WFD has been new or tightened phosphorus standards for STWs. In England and Wales, the WFD is expected to require some thirty percent of STWs to introduce phosphorus removal (EA, 2009). Phosphorus Reduction in Wastewater Treatment Where an end of pipe solution is required, phosphorus removal at STWs is enabled with a combination of biological, chemical and physical removal processes. Enhanced Biological Phosphorous Removal (EBPR) uses selection of specialised microbial populations capable of storing phosphorus in excess of their metabolic requirements, with the resulting captured phosphorus wasted as sludge (WEF, 2011). There are no EBPR plants in Scotland due to its dilute sewage concentrations. Elsewhere in the UK, EBPR is undertaken but remains challenged by dilution through infiltration and inflow, resulting low organic loads and by winter sewage temperatures (Black & Veatch, 2009). Where installed, EBPR may also require chemical phosphorus removal in addition to supplemental carbon dosing to enable sufficient carbon for treatment. Chemical phosphorus removal occurs through precipitation, surface complexation and solid-liquid separation due to dosing with hydrous metal oxides commonly iron or aluminium (WEF, 2011). The reaction consumes alkalinity and, in addition to removing phosphorus, enhances removal of solids as sludge in settlement stages. This creates significant additional sludges for transport and treatment. The requirement for metal salts dosing for phosphorus removal and as a coagulant in drinking water treatment applications has resulted in metals effluent standards being introduced and these alone may introduce a requirement for tertiary filtration to at some STWs. Phosphorus consents below 1 mg/l may also require tertiary filtration and such tertiary treatment stages retrofitted to existing STWs typically require re-lift pumping of all flows with substantial operating cost impacts. The Challenge: Phosphorus Removal and Carbon Emissions Reduction Hence, chemical phosphorus removal - widely used in the UK - increases energy and material requirements at STWs. The net increase in carbon emissions due to phosphorus reduction for WFD compliance is estimated at between twenty five to fifty percent in work by the Environment Agency (2009) though is highly dependent on the scale of the sewage treatment facility. Yet, in the face of WFD compliance, and corresponding emissions increase, the UK Water Industry is expected to achieve reduced carbon emissions. Within the Industry, carbon accounting and trade has recently been introduced through the Government s compulsory CRC Energy Efficiency Scheme which requires Water Companies to report, reduce and trade their emissions (DECC, 2010). EU member states have also committed to a twenty percent reduction in greenhouse gases below 1990 levels by 2020 and are required to meet renewables targets. With Page 4 of 8

5 considerable renewables potential, the Scottish Government have recently revised their national target from fifty percent renewable energy to eighty percent by UK Industry response Scotland s RBMPs developed under the WFD do not quantitatively consider climate change impacts of planned measures such as point source reduction through sewage treatment and the likely process for future prioritisation of planned measures considering economic (and carbon) costs is far from clear. The Environmental Agency of England and Wales (EA) in a recent report Transforming Wastewater Treatment to Reduce Carbon Emissions outlines five key strategies to mitigate increases in emissions due to WFD compliance (EA, 2009): 1. Source control recognising the greatest carbon savings but also the historic lack of control Water Companies have here. 2. Low carbon process solutions continued end of pipe treatment but at lower carbon cost. 3. Greater operational efficiencies improved aeration control, reduced treatment of storm waters, reduced infiltration through catchment intervention. 4. Redevelopment of existing treatment processes to less conventional lower energy technologies. 5. Renewable energy generation increased adoption of anaerobic digestion, on-site hydroelectricity generation. In considering compliance with the WFD and two scenarios of varying emissions reduction, the EA concludes that net emissions can be reduced - but only with a catchment based approach (EA, 2009). Recycling phosphates A further possibility to offset carbon emissions when considering phosphorus is its recovery through recycling as fertiliser. There is no EU requirement for P recycling other than for general beneficial reuse of sludges and wastewaters where possible (EC, 2006; OJ L, 1991). Recovery could be as urine, as sewage sludges or in effluent reuse. Agricultural slurries are already widely spread on land in the UK. With fifty percent of total household phosphorus excreted in urine in just one percent of waste volume, separation of urine at source as a fertilizer has been trialled in Sweden. Studies conclude that, though not without its social challenges, urine separation and direct application as fertiliser is a lower energy alternative to sewage treatment and conventional fertilizers (Jonsson, 2001). Once incorporated into sewage, phosphorus can be recycled as struvite through sidestream processes or recycled to land as fertilizing biosolids. Struvite production at a UK STW recently began in Slough however the process can only be adopted where biological not chemical phosphorus removal is undertaken (Thames Water 2010). While agricultural benefits of chemical P sludge application to land is recognised, precipitated phosphorus is less bioavailable to plants and contains potentially toxic contaminants (Hislop, 2008). Page 5 of 8

6 While unplanned indirect potable reuse has been widely practised in the UK 7 no agricultural irrigation schemes exist although reuse is an increasingly hot topic in water stressed Southern England. The Great Sludge Debate With chemical phosphorus removal increasing sludge production, this has considerable implications for sludge management and carbon footprints: Increased GHG emissions due to: Increased volume of sludge to be managed and transported; Reduced thickening capacity of chemically dosed sludges; Higher percentage of inert solids in sludges = increased aeration costs, lower energy potential; Reduced fertilizer value of chemical sludge than for non chemical sludges. Decreased GHG emissions due to: Potential for on site anaerobic digestion (AD) increases with increased sludge volume; Higher removal of organics in settlement increases biogas potential; Higher removal of organics in settlement means reduced aeration. The degree of interactions and importance of site specific treatment and disposal routes is evident; meaningful options evaluation and emissions assessment has to be site specific. Meeting Quality & Carbon Challenges The Water Industry has commitments to reduce its carbon footprint while increasing 7 As the River Thames Alliance remind visitors, a drop of rain falling in the Cotswolds will be drunk by 8 people before it reaches in the sea. the levels of phosphorus removal and has a role to play in economic analysis of treatment alternatives for prioritisation of planned measures under the WFD. As this work has shown, this will be challenging for the industry because: Significant catchment pressures are from sources the industry has had little historical control over - diffuse pollution, human consumption and detergents; While diffuse agricultural phosphorus pressures will be prioritised in WFD planning, this process will be slow. Point source discharges will remain a concern and easiest regulate; Nutrient balances on a catchment basis will be required to prioritise measures to improve water quality at least cost; The implications of chemical rather than biological phosphorus removal are worse from an emissions and reuse perspective but remain the reality for countries like Scotland with weak sewage strength; There is significant scope for reduction of STW energy consumption through improved process operation and control, heat and power generation from AD though only for larger scale STWs; There is scope for beneficial agricultural use at various stages of P removal from sewage but research continues and chemical P sludges are more problematic. Given the above, the industry s role in the effective reduction of phosphorus pollution (while reducing carbon emissions) is, perhaps, less clear. Significant phosphorus inputs appear beyond their control; the most obvious solutions appear to be upstream of STWs. Yet the catchment approach afforded by the WFD offers key opportunities for Page 6 of 8

7 participation in delivering the most effective methods of nutrient reduction and requires such participation. Key challenges to be addressed by the Industry must include: 1. Source reduction - WFD basin planning The water industry acknowledges a lack of control over source reduction (EA, 2009). However in England, water regulator OFWAT increasingly enables funding for catchment management activities proposed by Water Companies. With such participation by the water industry, meaningful catchment projects can be developed in place of, or to compare with, end of pipe phosphorus reduction solutions. The process must be iterative as focus on point source sewage pollution continues, the relative importance of diffuse sources increases (EEA, 2005). 2. Catchment based phosphorus balances With significant monitoring and data collection required under the WFD and the resultant development of interactive water quality mapping tools, the makings of a catchment scale nutrient assessment exist already and must be developed to enable the required prioritising of planned measures to improve water quality at least cost. 3. Challenge the need for treatment During the optioneering process, an opportunity has to be recognised for consideration of a no-action option or a reallocation of funds elsewhere to a more effective catchment water quality solution. Only when sufficient information becomes available in a project is this assessment likely possible: there must then be a forum for challenge of the catchment solution. 4. Challenge the process solution To succeed as a lower carbon wastewater industry and mitigate the impacts of phosphorus reduction and WFD compliance, significant efficiencies must be made at STWs. This must include challenge of the degree of treatment required, flexibility in licenses, and the pursuit of low energy construction and operational solutions. With carbon accounting now entrenched in the UK Water Industry, carbon assessment of treatment options must be undertaken.the industry must develop necessary tools for designers to have at their disposal. 5. Process design for nutrients and energy Identification of suitable reuse options for biosolids, effluents and energy on a catchment basis will allow more informed design choices to be made. However, the scale of treatment possible, available land bank, competition from farm slurries and lack of effluent reuse options may remain barriers to nutrient recycling (SW, 2006). Discussion and Conclusions The human relationship with phosphorus is interesting. As a non-renewable resource, our major phosphorus use in fertilizers is heavily reliant on fossil fuels, is set to increase to meet global food needs and yet significant excess amounts applied to soils are lost at the expense of diffuse agricultural pollution. At the same time, humans consume and excrete increasing amounts of phosphorus with this also set to increase. Unfortunately, we have identified a key water quality issue the result of our phosphorus emissions. In addressing this through the regulatory framework, the net impact of will be increased carbon emissions with a number of interdependent impacts on wastewater treatment, energy generation and sewage sludge management. Page 7 of 8

8 To participate in effective management of our anthropogenic phosphorus problem without further contributing to climate change, water industry practitioners must bravely step outside their site boundaries, understand phosphorus inputs and interactions, appreciate the catchment approach and engage effectively allow most effective management of water quality References Black & Veatch, Scottish Water Reporter's Report SR10 2nd Draft Business Plan. British Nutrition Foundation, Nutrient Requirements. British Nutrition Foundation. Available at: DECC, The CRC Energy Efficiency Scheme User Guide. EA, Transforming wastewater treatment to reduce carbon emission., Bristol, Environment Agency. EC, EC proposes to ban phosphates in laundry detergents. Available at: EEA, Source apportionment of nitrogen and phosphorus inputs into the aquatic environment, Luxembourg: European Environment Agency Office for Official Publications of the EC. Food Standards Agency, Risk Assessment Phosphorus. Available at: Hislop, H.(ed.) Review of the feasibility of recycling phosphates at sewage treatment plants in the UK, United Kingdom: DEFRA. Jones, D.C., UK Food Standards Agency Initial Opinion: Phosphated distarch Phosphase as Food Ingredient. Available at: Jonsson, H., Urine separation - Swedish experiences. In Proceedings from NJF-seminar No Urban Areas - Rural Areas and Recycling - The organic way forward. Copenhagen, DARCOF, p Neal, C. et al., Declines in phosphorus concentration in the upper River Thames Science of the Total Environment, 408(6), pp OJ L, /271/EEC Council Directive concerning urban waste water treatment. OJ L 327, 135, p.40. OJ L, Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy (entered into force 22 December 2000). OJ L 327, 43, pp Scottish Water, Draft National Sludge Strategy. Soil Association, A rock and a hard place - Peak phosphorus and the threat to our food security, Bristol: Soil Association. Available at: Thames Water, Renewable phosphate fertilizer from sewage: a UK first - News releases - Thames Water. Available at: U.S. Geological Survey, Mineral commodity summaries UKWIR, Source control of phosphorus from domestic sources, London: UKWIR Ltd. Uribarri, J. & Calvo, M.S., Hidden Sources of Phosphorus in the Typical American Diet: Does it Matter in Nephrology. Seminars in Dialysis, 16(3), pp Vaccari, D.A., Phosphorus: A Looming Crisis. Scientific American, 300(6), pp WEF, Nutrient removal, New York McGraw-Hill ;;WEF Press. Disclosures The author has nothing to disclose. Page 8 of 8