17
Use of Geographic Information Systems (GIS) to Calculate the Assimilative Capacity of Rivers to
Receive Proposed Discharges
Vivienne Kelly
Informatics & Reporting
Office of Environmental Assessment
t: 053-9160612
Presentation Outline
Introduction to Assimilative Capacity
Calculating Assimilative Capacity & Concentrations
Integrating Data Sources
Demonstration of GIS Assimilative Capacity Tool
Our Vision
Aim:
To develop environmental management systems that assess and report on environmental quality using integrated data from multiple data sources to provide more intelligence to data users see and to increase the efficient use of EPA resources.
Systems Developed:
Assimilative Capacity Tool
Risk Assessment Tool (Landfills, Quarries & Mines)
Assimilative Capacity
What is assimilative capacity?… the ability of a body of water to cleanse itself; its capacity to receive waste waters or toxic materials without deleterious effects and without damage to aquatic life or humans who consume the water.
How is it calculated?
Simple calculation: (AC = (cmax – cbackground) x (F95 or DWF) x 86.4)
Environmental Quality Standards (EQS) (cmax)
Background Chemical Monitoring (cbackground)
Hydrometric Flow (95%iles & DWF)
EPA Role? When assessing proposed discharges from IPPC, Waste and Waste Water Discharge Applications, the EPA must determine the capacity of a waterbody to receive the discharge and the potential environmental impacts.
Questions to Ask
River
Q1: What is the capacity upstream of the discharge?
Q2: What is the concentration following the discharge?
Q3: What proportion of the capacity has been
absorbed as a result of the discharge?
UWWTP
Calculations
Assimilative Capacity:
Non Toxic Substances AC = (cmax – cbackground) x F95 x 86.4
Dangerous Substances AC = (cmax – cbackground) x DWF x 86.4
The capacity of a water body is calculated in kg/day
Variables:
AC = Assimilative Capacity
Cmax = Maximum permissible concentration (EQS)
Cbackground = Background concentration in river
F95 = 95%ile flow in the river (m3/sec)
DWF = Dry Weather Flow in the river (m3/sec)
Other Calculations
Resultant Concentration:
Capacity Absorbed:
Cmax = Maximum permissible concentration (EQS)
Cfinal = Concentration in river after discharge of effluent
Cback = Background concentration in river
Ceffluent = Treated effluent concentration
Vflow = Volume of flow in river (95%ile or DWF – m3/sec)
Veffluent = Volume of effluent (m3/sec)
% AC Absorbed =(Cmax - Cback) - (Cmax - Cfinal)
(Cmax - Cback) x 100
Cfinal =(Cback x Vflow) + (Ceffluent x Veffluent)
(Vflow + Veffluent)
Waste Water Discharge Licence Substances
1 Suspended Solids
2 Ammonia (asNH4)
3 Biochemical Oxygen Demand
4 Chemical Oxygen Demand
5 Total Nitrogen (as N)
6 Nitrite (as N)
7 Nitrate (as N)
8 Total Phosphorous (as P)
9 OrthoPhosphate (as P)
10 Sulphate (SO4)
11 Phenols (C6H5OH)
Relevant Substances
Total Substances = 31Total Calculations = 93
Per Discharge Point
Assimilative Capacity WebGIS Tool
The Assimilative Capacity Tool is a web based GIS application designed to allow licence inspectors to calculate the capacity of rivers and the surrounding environment to receive pollutants from waste water treatment discharges.
Function:
Determine the capacity of waterbodies to receive specific pollutants from proposed discharges.
Determine the potential impacts to the surrounding environment.
Improve the use of resources & produce better response times.
Support decision making.
Discharge Point
Hydrometric Station
Monitoring Station
River Flow Direction
ENGINE
Hydrometric Data
AQUARIUS
Assimilative Capacity at Proposed Point of Discharge
Hydro Flow Data
Water Quality Data
Proposed Limit
Calculation
Proposed Discharge
Run
Engine
Model Concept
Integration of Internal & External Data
Demonstration
12 Atrazine 22 Cyanide
13 Dichloromethane 23 Flouride
14 Simazine 24 Lead
15 Toluene 25 Nickel
16 Tributyltin 26 Zinc
17 Xylenes 27 Boron
18 Arsenic 28 Cadmium
19 Chromium III 29 Mercury
20 Chromium IV 30 Selenium
21 Copper 31 Barium
Dangerous Substances
Assimilative Capacity Tool Demonstration
Table of Contents
Toolbar
Zoom to Area of Interest
Zoom to Area of Interest
Discharge Point
Upstream Monitoring Point
Downstream Monitoring Point
Select Assimilative Capacity Tool
Select Discharge Point
Summary of local EPA Monitoring Stations
Click to Highlight Station on Map
Click Next
Hydro Data
Report Window Appears
User Selects Required Report
Summarry Information on Discharge
Map of Discharge
EQS Exceeded Prior to Discharge
Option to Change EQS
User Selects New EQS, Saves andRe-runs Report
With New EQSCapacity is not
Exceeded.
Select Environmental Report
River Data
Water Quality Up & Down Stream
Conservation Data
Other UWWTP’s
Caveat
Decision Support Tool Indication of waterbody capacity, not absolute rule Inspectors must have full understanding of EQS for a site
and ensure appropriate data used in any calculation All borderline cases should be examined in full
Improved Resource Use
EPA Aim: To increase the efficient use of EPA resources Manual Effort: 4-6 days No. of Discharges: 177 Approx. Time to Calculate Manually: 3yrs Total Time using AC Tool: 4 days
Development Team
EPA Team: Breen Higgins Gavin Smith Fiona O’Rourke Deirdre Kirwan Tom Stafford Ozan Emem Jason Larkin Claire Byrne Aisling McElwain George McHugh
Compass Team: Ken Dowling Pavel Janda Seth Girvin Maurizio Taddei Mick Lennon
THANK YOU
