Environmental Discharge Objectives

Environmental Risk Assessment (ERA)

The GMWC Environmental Risk Assessment study was carried out by Natech Environmental Services Inc. and GMWC. The study was developed in support of the implementation of the Canada-wide Strategy for the Management of Municipal Wastewater Effluent (MWWE). The ERA study had four phases of work:

Phase 1 required developing a list of substances of potential concern and an effluent initial characterization program implementation. The initial characterization program was carried out from January to December 2011.
Phase 2 included developing and running a mathematical model to simulate the hydraulics of the Petitcodiac River and predict the mixing of the WWTP effluent in the river
Phase 3 primarily involved field investigations in 2011. The field work included observations of the hydrological characteristics and water quality of the Petitcodiac River estuary, and measurements of the effluent mixing regime in the river.
Phase 4 consisted of the determination of Environmental Quality Objectives (EQO), mixing zone sizes, and Effluent Discharge Objectives (EDO), based on the findings of the Phase 1 and Phase 2 investigations.

This study was completed in April 2014 and submitted to the New Brunswick Department of Environment and Local Government in May 2014 for approval.

Environmental Quality Objectives (EQOs)

EQOs are objectives to be met in the specific receiving environment in this case the Petitcodiac River. EQOs where established based on natural background concentrations in the river and water quality guidelines values*.

Once established an EQO for a particular substance became an input to a model used to back-calculate Effluent Discharge Objectives (EDOs) that applies to the effluent discharge. EDOs would ensure that water quality should not be degraded beyond the ambient level and that all practical measures should be taken to upgrade the water quality.

*The guidelines values were obtained from the Canadian Water Quality Guidelines for the Protection of Aquatic Life (CCME, 2014) for estuarine and marine waters, the Guidelines for Canadian Recreational Water Quality (Health Canada, 2012), and the National recommended Water Quality Criteria from USEPA (2011).

Environmental Discharge Objectives (EDOs)

Effluent Discharge Objectives (EDOs) are effluent quality objectives that were calculated based on the Environmental Quality Objectives (EQOs), and the dilution available at the edge of the allocated mixing zone under the worst-case scenario (1 in 10 for the existing outfall), and measured background concentrations in the Petitcodiac River. The National Performance Standards (NPS) set in the Federal Wastewater Systems Effluent Regulations (Fisheries Act -June 2012), were included as EDOs.

Table 1: Proposed EQOs for the Petitcodiac River and EDOs for GMWC effluent discharge

Parameter	Unit	Assumed Background		EQO^*	EDO^*	Effluent quality
Parameter	Unit	River	Ocean	EQO^*	EDO^*	Effluent quality
CBOD5	mg/L			NA	<25 ^(NPS)	58
DO	mg/L	varies		>8	>5	NA
TSS	mg/L	10	>500	<5 - 25	<25 ^(NPS)	61
Unionized NH₃	mg/L			NA	<1.25 ^(NPS)	NA
NH₃-N Total	mg/L	0.1		<1.0	<9	12
TN	mg/L	0.40	0.10	<0.55	<25	20
TP	mg/L	0.020	0.026	<0.05	<1.7	2.5
pH	units	8.0		7.0 - 8.7	6.0 – 9.6	6.1 – 7.8
E. Coli	MPN/100m	100	5	<200	<200	780,000
Faecal coliforms	MPN/100m	300	5	<14	<10,000	2,000,000
Arsenic	µg/L	1		<12.5	<116	<1
Cadmium	µg/L	0.08		<0.12	<0.48	0.11
Chromium	µg/L	1		<1.5	<6	1.8
Mercury	µg/L	0.01		<0.016	<0.07	<0.025
PCBs	µg/L	0		<0.01	<0.1	<0.01
Endosulfan	µg/L	0		<0.002	<0.02	<0.01
Naphtalene	µg/L	0		<1.4	<14	0.2
Benzene	µg/L	0		<110	<1,100	<0.5
Toluene	µg/L	0		<215	<2,150	1.8
Ethylbenzene	µg/L	0		<25	<250	<1
1,2 Dichlorobenzene	µg/L	0		<42	<420	<0.5
Acute toxicity	TU	0		<1	<1	<1 - 1.4
Chronic toxicity	TU	0		<1	<10	< 1 - 3.2

NPS: National Performance Standard (Wastewater Systems Effluent Regulations-June 2012)