Sizing oxidation pond treatment systems (6-2)

Transcription

1 Sizing oidation pond treatent systes (6-2) Oidation treatent systes coprise two or ore sealed ponds in a series. One of the ost coon reasons for the poor perforance of effluent pond treatent systes is undersized ponds. Intensification has led to ore efficient ilk production but it has also led to increasing aounts of effluent being generated at the far dairy. Unless your effluent treatent syste has been upgraded to cater for this increased effluent, then the eisting effluent syste ay be inadequate. Poorly perforing oidation ponds can lead to a decline in water quality and nuisance effects fro odour. See Farfact 6-1: How effluent oidation ponds work. Poor design and inadequate aintenance will result in poor pond perforance Investigate the local regulations and cost before deciding on an option involving pond systes. The figure below outlines the planning procedure and the factors influencing the decision to construct oidation ponds and the design of the pond syste. Always use a suitably qualified effluent engineer to provide advice when designing or upgrading an oidation pond syste. In any areas, regional councils have indicated they do not see the oidation pond syste, with discharge to waterways, as an acceptable or sustainable practice under the Resource Manageent Act (1991). Land application of effluent, as an alternative, has the double benefit of retaining and utilising nutrients on far and having better water quality outcoes than typical oidation systes. Optiu conditions for oidation ponds The pond syste will not work well if: It is too sall Teperatures are below 20 C A lot of botto sludge has built up The retention tie is less than 60 days Indicators of a poorly operating pond include: Sludge build-up or ecessive crusting Bubbling has stopped in the anaerobic pond Discolouration of the receiving waterway Bad sells fro the receiving waterway Septeber 2012

2 Farfact 6-2 Septeber 2012 Page 2 of 5 PROCEDURE FOR PLANNING A POND SYSTEM Peak volues and loading Identify the volue, BOD and pollutant loading Topography, cliates, waterways and soils Identify the physical liitations of the property Pond systes as an initial treatent Meet Regional Council and Food Safety requireents Pond site selection Select a suitable site for the pond syste Anaerobic pond syste Calculate the surface area required. Consider depth, surface area orientation and future herd size increases Pond syste add-ons Consider the use of echanical aeration, anaerobic digestion or additive treatents to iprove effluent quality. Pond systes as an initial treatent Consider using the ponds as an initial treatent before additional ponds, land application or wetlands Pond syste construction Pay attention to pond liners, ebankents, batter slope, stor water control, piping, and fencing Pond syste anageent Correctly carry out pond start up and pond aintenance

3 Farfact 6-2 Septeber 2012 Page 3 of 5 How big should the ponds be? The following pages provide a guide to deterine whether your effluent pond treatent syste is adequate for the size of your herd and details if you are planning to increase the size of your herd. Use this worksheet as a guide only the accuracy will be deterined by the quality of the inforation used. The calculations in this worksheet are based on the following assuptions: 50 litres per cow per day total effluent fro the far dairy; can vary fro 30 to 100 litres 100:1 (100 litres of water to 1 litre of effluent) dilution factor in the receiving water. Lower dilution ratios ay deand an additional treatent such as a constructed wetland. You will need the following inforation: Cow nubers (aiu ilked) Current effluent pond sizes easure diensions fro the level of the effluent in the pond (see diagra) First (anaerobic) pond depth can be easured with a long pipe (paint increents on it so you can see the readings). Anaerobic and Aerobic Pond Length () Anaerobic Pond Depth () Level of effluent in pond Anaerobic and Aerobic Pond Width () Step One: Storwater diversion Is storwater fro your dairy shed and surrounding land diverted fro entering the pond treatent syste? Step Two: Calculate volue of anaerobic (first) pond Measure the diensions of your anaerobic pond: Length Width Depth 3 (A) (A) Anaerobic Pond Volue 3 (B) Accounts for a 2:1 batter slope

4 Farfact 6-2 Septeber 2012 Page 4 of 5 Now deterine the recoended volue for your herd size: No. of Cows X Recoended volue per cow (fro table) Use this table to deterine the recoended volue for your anaerobic pond nuber of cows per cow volue. Your Actual Volue (B) 3 3 Region Northland, Auckland, Waikato, BOP, Gisborne, Hawkes Bay Manawatu, Wanganui, Taranaki, Wellington, Marlborough, Tasan, Nelson, Canterbury West Coast, Otago, Southland Recoended Volue per cow for Anaerobic Pond** **Assues storwater fro the dairy shed and surrounding land is NOT entering the pond. A larger volue will be required if this is not the case. Does your anaerobic (first) pond eet the recoended volue for the size of your herd? Step Three: Solids retention Are the solids retained in your anaerobic (first) pond by an effective baffle or T-piece? (outlet pipe between ponds) Step Four: Calculate surface area of aerobic (second) pond Measure the diensions of your aerobic pond. Where you have ore than one aerobic pond, work out the surface area of each pond then total the: Width Length Surface Area Aerobic Pond One Aerobic Pond Two (if relevant) Aerobic Pond Three (if relevant) Total Surface Area of all Aerobic Ponds 2 (C)

5 Farfact 6-2 Septeber 2012 Page 5 of 5 Now deterine the recoended surface area for your herd size: Recoended Surface Area No. of Cows X Recoended surface area per cow (fro table) Use this table to deterine the recoended surface area for your aerobic pond nuber of cows per cow surface area. Your Actual Surface Area (C) 2 2 Region Northland, Auckland, Waikato, BOP, Gisborne, Hawkes Bay, Manawatu, Wanganui, Taranaki, Wellington, Marlborough, Tasan, Nelson, Canterbury, West Coast, Otago, Southland Recoended Surface Area per cow for Aerobic Pond** **Aerobic ponds should be no deeper than 1.2. Does your aerobic (second) pond/s eet the recoended surface area for the size of your herd? Step Five: Effluent contribution fro stand-off and/or feed pad Is your pond syste designed to cater for effluent fro your stand-off / feed pad areas? So what does this ean? If you have answered to all these questions then the pond treatent syste should perfor adequately. If you have answered NO to any of these questions, you ay find that your pond syste is inadequate for the size of your herd. If so, consult with your regional council or an effluent engineer specialist for design advice. Septeber 2012 DairyNZ 2012