Polypipe Continuing Professional Development. Rainwater Harvesting In The Sustainable Environment

Transcription

1 Polypipe Continuing Professional Development Rainwater Harvesting In The Sustainable Environment

2 Introduction to Polypipe Terrain

3 Aims and Objectives The Sustainable Environment The Concept of Rainwater Harvesting Legislative Changes & Drivers The System Maintenance Requirements Life Cycle Costs Summary & Conclusion Open Forum

4 The Sustainable Environmental Flooding as a result of extreme storms similar to those of the summer 2007: 57,000 homes were affected by surface water flooding Damage estimated to be around 3 billion Currently 80,000 homes in the UK have a 10% annual chance of suffering surface water flooding with the likelihood of damages estimated at 270 million per annum.

5 The Sustainable Environment Climate Change is driving the need for innovative solutions for surface water management Average UK annual temperatures may rise by C by the 2080 s Seasonal distribution of rainfall will change significantly with the possibility of winters becoming wetter. Sea levels are expected to rise by between 90 to 690 mm Increase in the prevalence of extreme weather events

6 The Sustainable Environment Exceptionally low rainfall Substantially below average Below average Normal range Above average Substantially above average Very Wet With the exception of the South West, the whole of the UK has seen above average rainfall compared with the average Source Met Office

7 The Sustainable Environment The water stress method takes a long-term view of the balance between water availability and the demand for public water supply, rather than a snapshot of shorter or peak periods. For most companies (Water Supply Undertakers), the largest component of increased demand is customer water consumption; in other words it predicted that we will nearly all use more water in our homes in the next 25 years. Serious Moderate Low (Environment Agency 2007)

8 The Sustainable Environment 95% 5% Natural Undeveloped Land 5% 95% Developed Land

9 The Sustainable Environment Source OFFWAT Potable water is not as abundant in England and Wales as you would think. We only have 1,334 cubic metres (m3) per person a year much less than France (3,065 m3) or even the hotter Mediterranean countries of Italy (2,785 m3) and Spain (2,775 m3). South East England has even less water per person due to its high population density. The Thames Valley has only 266m3, only a fifth of the England and Wales average. The average person in England and Wales uses 150 litres of water every day. Most of it is used for washing and toilet flushing, but it also includes drinking, cooking, car washing and watering the garden. We use almost 50% more water than 25 years ago.

10 The Sustainable Environment For most companies (Water Supply Undertakers), the largest component of increased demand is customer water consumption; in other words it predicted that we will nearly all use more water in our homes in the next 25 years. Environment Agency

11 Domestic Water Consumption

12 Commercial Water Consumption

13 Market Sectors Housing Commercial / Industrial / Retail Agricultural / Animal Shelters Education Leisure Utilities Ministry of Defence Hospitals Fire, Police and Ambulance Stations Airports

14 Rainwater Harvesting Applications Housing Speculative Social Self Build

15 Rainwater Harvesting Applications Commercial / Industrial / Retail Commercial Industrial Retail

16 Rainwater Harvesting Applications Agricultural / Animal Shelters Organic Farming Horticulture Animal Husbandry Animal Sanctuaries

17 Rainwater Harvesting Applications Educational Universities Secondary Schools Primary Schools

18 Rainwater Harvesting Applications Leisure Golf Clubs Swimming Pools Football Stadia

19 Assessment Criteria Principal use and location Roof area Roof Construction Number of occupants Applications for rainwater Peak and total water demand Gravity or pressurised system Rainfall data Water supplier Detailed requirements Health and Safety considerations

20 Assessment Basic Information Requirement To allow even a budget specification and quotation to be prepared for the client, the following information will be required Site Location This will allow us to use the correct rainfall average and will also define the water company in the area thus allowing us to calculate the water cost saving. Roof Area & Material The surface area of the roof used for harvesting purposes is required. Drainage System Used Commercial roofs will either have standard gravity downpipes or siphonic downpipes. Siphonic systems will increase the flow rate thus affecting the filter chosen

21 Assessment Type of Site Is the site a school, an office, domestic housing, industrial etc Population on site Split in to Male & Female. How many of each on site. Site Hours of Use How many hours per day, how many days per week etc Use for Water Toilets, irrigation, vehicle washing, industrial etc If non standard use, try to find out quantity used. Delivery of Water How will the water be delivered to the appliances? Via a header tank, a booster set or direct to appliances. Pump Duties Rarely available at this stage. Pumping distance. Flow requirement. Pressure requirement. Pipe work size etc.

22 Legislation, Regulations & Drivers British Standards BS 8515:2009 Now seen as the definitive guide for Rainwater Harvesting design Public Health considerations Document L8 BREEAM Water Supply Regulations Building Regulations considerations

23 Important References Part H of The Building Regulations Planning Policy Guidance Note PPS 25 WRAS Information and Guidance Notes The Private Water Supply Regulations The Water Supply (Water Fittings) Regulations HSC Document L8 for the control of Legionella CIRIA Notes C359 & PR080 Delayed Part G of The Building Regulations

24 Legislation British Standard BS-8515:2009 In 2002 Approved Document H changed the hierarchy of drainage and drainage design considerably Consider rainwater harvesting first and foremost Attenuation or if ground conditions permit, a soak away structure may be used Discharge to sewer or watercourse may only be considered as a last resort PPS 25 -the EA to have a wider consultation role and recommends upsizing drainage by over 20% to cope with future building and climate change Government Future Water Strategy launched together with a consultation on improving surface water drainage 2009 Water Framework Directive starts to be implemented

25 Future Water Strategy Sets out how Government wants the water sector to look by 2030 with the following main aims : reduced water demand by reducing average per capita water consumption from 150l/p/d to 120l/p/d Improved water supply with more reservoirs and fewer abstraction licenses Encourages rain water harvesting Improve water quality in the natural environment Water Framework Directive (2009). Improve surface water drainage by implementing SUDs Reduce flooding risk from rivers and coasts by more integrated strategic planning Near universal water metering in water stressed areas Code for Sustainable Homes BREEAM

26 Concepts of Rainwater Harvesting

27 Rainwater Harvesting Rainwater harvesting systems collect run-off from a roof and stores the rainwater in an appropriately sized tank. Water is then pumped back into the building for use in non-potable applications such as toilet flushing, urinal flushing and commercial wash down areas. Surface water from car-park areas can also be collected with rainwater only with a purpose designed treatment filter is used for the surface water On average, 63% of the water used within a commercial building is not required to be of a potable standard and therefore rainwater can be used in these applications.

28 Gravity System Captured water is pumped from the primary storage tank to a header tank at high level within the building Water in the header tank is distributed to the point of use via gravity Pump option to boost the supply to particularly remote outlets Mains water top up directly to the header tank Available in single and duty standby pump arrangements Back up function ensures that water supply is maintained even in the event of power failure

29 Pressurised System Electronic control system monitors demand for water Water is pumped directly from the main storage tank directly to the point of use The control system measures water level in the tank and imports mains water if required to prevent the system running dry Delivers water under greater pressure Space saving no need for header tank Available in single and duty standby pump arrangements

30 Filtration A Rainwater Harvesting System usually incorporates 3 forms of filtration Pre-tank filter (leaf filter) Floating filter on the pump In-line filter within the property A fourth form of filtration will be incorporated if the system installed includes UV Disinfection. All filters within the system should be cleaned regularly in accordance with manufacturers instructions

31 System Components FILTERS As stated in BS8515, filters must Be water and weather resistant Removable and accessible for maintenance purposes Have an efficiency rating of at least 90% Pass a maximum particle size of less than 1.25mm All filters must conform to these specifications even sedimentation chambers

32 Pre-Tank Filters Filter options for a wide range of internal and external applications

33 Calculating Tank Size As stated in BS:8515 there are 3 different calculation methods Simplified Approach Intermediate Approach Detailed Approach Simplified Approach Usually used for domestic dwellings and is based on roof area/annual rainfall/no of inhabitants Intermediate Approach A little more in depth, with set equations used to calculate tank sizes based on either available yield or demand Detailed Approach Used to calculate storage size more accurately when, demand is irregular, yield is uncertain or costly or larger rainwater harvesting systems are proposed Usually all calculations are based upon storing 5% of annual rainfall (18 days) DREAM Assessment Method calculates RWH tank sizes on 14 days and NOT 18!

34 Calculating Tank Size from available yield We would in normal circumstances use the Intermediate approach Y r = A x e x h x n x 0.05 (18/365) Where Yr = annual rainwater yield (L) A = collecting area in m 2 e = yield co-efficient (%) h = the depth of annual rainfall in mm n = hydraulic filter efficiency (%)

35 Calculating Tank Size - demand Tanks should be sized based upon 5% of the annual demand D n = P d x n x 365 x 0.05 Where D n = annual non-potable demand P d = the daily requirement per person n = number of persons BOTH of the above calculations are outlined in BREEAM

36 Calculation constants & variables Yield or roof co-effient Pitched BS:8515 states between BREEAM States between Flat BS:8515 no guidance BREEAM between Green/Sedum Roofs No guidance in either generally taken as 0.4 as no other information is available Variations above are due to different roof materials

37 Calculation constants & variables Filter efficiency is taken as 90% - co-efficient of 0.9 Annual Rainfall Data taken from Met Office based on published Regional variances Storage 5% of annual yield 18/365 days 5% of annual demand 18/365 days This may differ when using the Detailed approach Daily demand/requirement per person is dependant on No of people Flush volume Toilet visits Sex

38 System Components - Tanks Domestic tanks usually from 1,500 litres to 6000 litres Commercial tanks from 7,000 litres to 300,000 litres Commercial GRP tanks in standard, medium & heavy duty depth based on application and water table Concrete Tanks Plastic tanks now available in larger sizes

39 Above Ground Tank Options Sectional GRP Tanks Internal plant room applications Sizes from 1m 3 to 100m 3 Specialist erection on site WRAS Approved Insulated with 40mm polyurethane Used in conjunction with pump booster set or combined control units

40 Typical system

41 System Components Components Pump Floating filter Inline filter Controller Combined Systems

42 Post Installation Inspection Commissioning is the final stage when the system is shown to be functioning properly and is ready to hand over to the customer. In order to ensure that the system is going to work properly the developer must ensure that :- No debris is left inside the tanks or pipe work The system has been pressure tested and is watertight Filters are correctly housed The level sensor is correctly positioned Warning gauges are correctly calibrated The pump is correctly suspended (if it is in the tank) The control panel is working with all components The valves are working properly The mains back-up valve is working The system operates correctly in all actions at full pressure with no leaks or weeps.

43 Ultra-Violet Disinfection Unit BS8515 states that UV Disinfection for toilet flushing alone is not a standard requirement Systems that generate water vapour or mist should be treated Neutralises a wide range of bacteria including Legionella Design restricts shadowing ensuring optimum treatment efficiency Wide range of units available Regular maintenance is essential

44 Typical Pressurised System Layout

45 Gravity System

46 Combined Pressurised Systems Below Ground Option

47 Gravity System

48 Tanks and overflow

49 Pipe Identification

50 Life Cycle Costs Rapid payback periods Reduced investment requirements Minimum 25 year design life Low operating costs, typically 3p per cubic metre delivered ECA Enhanced Capital Allowance

51 Maintenance Requirements Leaf Filter Tank Components U V Filter

52 Summary and Conclusion The Sustainable Environment The Concept of Rainwater Harvesting Legislative Changes & Drivers The System Maintenance Requirements Life Cycle Costs Summary & Conclusion Open Forum The safe integration of this technology into our everyday working, living and sustainable environment