Dry Drains Forum 2009 Leaving a Sustainable Future Don Boynton

Presentation Outline Case for Sustainable Design Reduced Flows in Drains Chemical and Biological Activity Leaving a Sustainable Future

Case for Sustainable Design

Sustainable Development - more than green solutions 2005 World Summit’s three pillars of sustainability declaration: 1.Environment 2.Society 3.Economy

Sustainable Design – more than green solutions Sustainable Design Decision Model:  Environmental  Economic  Social  Time / Program  Quality “The old decision model is based on a balance between cost [economic], schedule [program] and quality. However, designers also need to become equally familiar with the effect their decisions have on the environment and human health, safety and comfort [social].” Mendler, S. Odell, W. Lazarus, M A. (2006) The HOK Guide Book to Sustainable Designs. 2 nd Edition. New Jersey: John Wiley & Sons, Inc.

Reduced Flows in Drains

Average Velocities in Pipework Average velocity in pipework of a WC discharge based on the mean flow rate from the WC in DN 100 and DN 150 Pipework. Gradients used are 1:60 (1.67%) for DN 100 and 1:100 (1.0%) for DN 150. To achieve 9L flush average velocities from a 4.5L flush WC, nominal pipe gradients need to be: 1:40 (2.5%) for DN 100; and 1:65 (1.54%) for DN 150

Modelling of Drainage Pipework Model boundary conditions  DN 100 uPVC pipework;  Pipework installed at a 1:60 (1.67%) gradient;  45° Junction with branch installed at 1:60 (1.67%) gradient; and  Single Toilet Flushes based on 4.5 L and 6 L capacity cisterns. Four monitoring points.  2m downstream of junction – Velocity (GREEN).  Centre of Junction – Velocity (RED).  2m upstream of junction – Velocity (BLUE).  Side branch pipe – Flux (flow in and out of branch) (BROWN) Modelling by L Erakovic. GHD Melbourne.

Modelling of Drainage Pipework Play Video Discharge rate based at head of drain based on the chart below. 4.5 L Flush 6 L Flush

Modelling of Drainage Pipework Play Video 4.5 L Flush 6 L Flush Modelling by L Erakovic. GHD Melbourne.

Model Analysis – Velocity 4.5L Flush. 6L Flush. Modelling by L Erakovic. GHD Melbourne.

Model Analysis - Flux Water flux into the junction branch pipe (kg/s), negative values indicate flow in and positive values flow out (return flow) of junction pipe. 4.5L Flush. 6L Flush. Modelling by L Erakovic. GHD Melbourne.

Model Analysis – Flux and Velocity 4.5L Flush. 6L Flush. Modelling by L Erakovic. GHD Melbourne.

Chemical and Biological Activity

Changing Characteristics of Sewerage COD BOD Trade Waste Limits Higher Strength Sewerage Longer retention times in domestic drainage systems. Increased risk of odour issues. Increased risk of Sulphide Production. Sewerage characteristics based on residential apartment TSS – Total Suspended Solids BOD – Biological Oxygen Demand (5 Day) COD – Chemical Oxygen Demand

Municipal Sewerage Observation Water authorities are observing strengthen sewerage. Water efficiencies resulting in reduced sewerage inflows. This chart:  BOD trending to strengthen. m =  COD trending to weaken. m =  Daily flow trending to reduce. m = Concern of retained materials in sewers.

Sulphide Production vs Temperature As temperature increases, the potential for Sulphide Production increases. Study by C Marree. GHD Townsville

Sulphide Production vs Velocity As velocity decreases, the potential for Sulphide Production increases. Study by C Marree. GHD Townsville

Sulphide Production vs BOD As BOD increases, the potential for Sulphide Production increases. Study by C Marree. GHD Townsville

Green House Gases Methane  Methane is produced in wastewater systems by the anaerobic metabolism of organic material by micro-organisms.  Reductions in sanitary plumbing and drainage flows will see longer retention times and higher concentrations of methane, or the production of methane in sanitary pluming and drainage where this has previously not occurred. Study by C Marree. GHD Townsville

Leaving a Sustainable Future

Where to from here? Stewardship of our water supplies is essential. There is no silver bullet solution. Solutions are affected by local conditions. Higher quality of design and installation. Can we achieve this? Ventilation of sanitary systems becomes more critical in odour control. Design standards should not be so concerned with probable simultaneous flows, but examine low flows and the geometry of the pipework. Prima-facie Environmental Sustainable Solutions need to be challenged to ensure that the other sustainable elements are not compromised and thus not providing a truly sustainable solution.