Projects
Clashnessie Water Quality Modelling
added on Tuesday 14th November 2006 by Ian Fraser
Client: Matheson Mackenzie Ross Architects
Project Value: Less than £10,000.00
Gunn MacPhee & Associates were engaged by Matheson Mackenzie Ross Architects, in September 2006 to undertake a study and modelling of the wastewater discharge from a private residential cottage in the village of Clashnessie.
Scottish Natural Heritage (SNH) had raised concerns at the planning stage that the proposed extension to the cottage and subsequent wastewater treatment discharge would increase the risk of pollution of the Abhainn Clas An Eas River. The river supports a population of freshwater pearl mussels (Margaritifera margaritifera) whose survival could be threatened if the river pollution levels increased.
The Abhainn Clas An Eas is an ungauged river so no data existed regarding flows or volume of water for the river. In order to identify the risk of pollution a desktop exercise was carried out to estimate the following variables:
· The total catchment area for the Abhainn Clas An Eas River
· The local Hydrogeological data within the catchment area
· The Standard Average Rainfall for the catchment area
· The Annual Potential Evaporation for the area
Using this data GMA were able to carry out statistical estimates to determine the low flow levels of the river. A Mass Balance Equation then determined that the discharge from the wastewater treatment when mixed and diluted by the river still produced an acceptable water quality suitable for the freshwater pearl mussels.
To confirm the results a Statistical Monte-Carlo simulation was conducted with 1,000 repetitions. This indicated that at the 95th percentile based on a Log Normal distribution both the Biochemical Oxygen Demand (BOD) and Ammoniacal Nitrogen (NH4-N) levels in the water were safe for the mollusc population.
Gunn MacPhee & Associates were therefore able to show statistically that the proposed treatment for the cottage discharge would reduce the BOD and NH4-N to a sufficiently low level continuously to maintain the water quality of the Abhainn Clas An Eas suitable for the Margaritifera margaritifera population.
Project Value: Less than £10,000.00
Gunn MacPhee & Associates were engaged by Matheson Mackenzie Ross Architects, in September 2006 to undertake a study and modelling of the wastewater discharge from a private residential cottage in the village of Clashnessie.
Scottish Natural Heritage (SNH) had raised concerns at the planning stage that the proposed extension to the cottage and subsequent wastewater treatment discharge would increase the risk of pollution of the Abhainn Clas An Eas River. The river supports a population of freshwater pearl mussels (Margaritifera margaritifera) whose survival could be threatened if the river pollution levels increased.
The Abhainn Clas An Eas is an ungauged river so no data existed regarding flows or volume of water for the river. In order to identify the risk of pollution a desktop exercise was carried out to estimate the following variables:
· The total catchment area for the Abhainn Clas An Eas River
· The local Hydrogeological data within the catchment area
· The Standard Average Rainfall for the catchment area
· The Annual Potential Evaporation for the area
Using this data GMA were able to carry out statistical estimates to determine the low flow levels of the river. A Mass Balance Equation then determined that the discharge from the wastewater treatment when mixed and diluted by the river still produced an acceptable water quality suitable for the freshwater pearl mussels.
To confirm the results a Statistical Monte-Carlo simulation was conducted with 1,000 repetitions. This indicated that at the 95th percentile based on a Log Normal distribution both the Biochemical Oxygen Demand (BOD) and Ammoniacal Nitrogen (NH4-N) levels in the water were safe for the mollusc population.
Gunn MacPhee & Associates were therefore able to show statistically that the proposed treatment for the cottage discharge would reduce the BOD and NH4-N to a sufficiently low level continuously to maintain the water quality of the Abhainn Clas An Eas suitable for the Margaritifera margaritifera population.