Wastewater treatment


1: Pumping & Screening
2: Grit Removal
3: Primary Settling
5b: Bioreactors
5b: Secondary Settling
6b: UV Disinfection


4a: Sludge Dewatering
5a: Biosolids Stabilzation
6a: Composting

Advanced biological wastewater treatment

The Wastewater Treatment Facility (WWTF) was initially constructed on the basis of an advanced chemically assisted primary process able to meet the regulatory discharge limits under the Approval to Operate.

Environmental Risk Assessment (ERA)

Under the new regulatory framework, the GMWC needed to complete an Environmental Risk Assessment (ERA) which is now in the review process with the provincial Department of Environment and Local Government. This work consisted of characterizing the effluent and determining effluent discharge objectives considering the impact on the receiving stream. The ERA will be used in setting the basis of design for the biological process and also in developing the combined sewer overflow (CSO) treatment strategy.

Pilot plant

Even though the new regulations came into effect in June 2012, the GMWC had been evaluating processes to determine the best suited and most sustainable approach to meet new regulatory limits well ahead of this. A report entitled Advanced Biological Treatment Process Selection by Conestoga-Rovers & Associates dated April 2010 outlines the options, considerations and basis for the recommendation to implement an advanced biological process, namely a biological nutrient removal (BNR) in the MLE (Modified Ludzack-Ettinger) or A2O (anaerobic-anoxic-aerobic) configuration.

In 2013, the Commission completed the pilot testing program in association with Conestoga-Rovers & Associates. This was followed by the compilation and analysis of all data, computer modelling and drafting of the basis of design along with tank layouts.

Environmental Impact Assessment (EIA)

An Environmental Impact Assessment (EIA) process was initiated in 2010 with the filing of the EIA registration document. This first step was needed to present the overall project (Long-term Sustainable Wastewater Collection and Treatment Strategy) focusing on treatment, conveyance and CSO elements and their potential environmental impacts, benefits and mitigation measures. Public meetings were also held to present the overall long-term strategy. As the project evolves, individual projects will be filed as well and screened as per the EIA process. Further public consultations through open houses will be held as needed and for more specific projects having a direct impact on a neighbourhood or the region.

Preliminary design

The above-described pilot work and development of the design basis was used as the framework for a Request For Proposals (RFP) to consulting engineering companies to undertake the preliminary design and detailed design of the plant upgrade to biological treatment. The GMWC issued an RFP in November 2013. Award of this contract was made in early 2014 for the preliminary design phase and to be followed by detailed design once the funding and procurement approach have been established. The objective is to complete this construction by 2018-2019 prior to the 2020 regulatory compliance deadline. The preliminary design phase of the project looks at tank configuration, equipment review, process control, hydraulics, plant retrofit, etc.

The new Wastewater Systems Effluent Regulations (WSER) made official in 2012 require that wastewater facility effluents must not be acutely lethal and must also meet the following conditions at the final discharge point to be authorized to be discharged:

  • The average carbonaceous biochemical oxygen demand (CBOD5) must not exceed 25 mg/l
  • The average concentration of total suspended solids in the effluent must not exceed 25 mg/l
  • The average concentration of total residual chlorine in the effluent must not exceed 0.02 mg/l
  • The maximum concentration of un-ionized ammonia in the effluent should be less than 1.25 mg/l, expressed as nitrogen (N), at 15˚C ±1˚C

The GMWC has thus moved forward with the pre-design of the biological treatment upgrade along with associated processes as a first phase and then proceeding to a detailed design stage based on the outcome of the pre-design and subject to the procurement/funding approach chosen for implementation. Upon completion of the design phase, construction is anticipated to take place in the 2015-2019 timeframe.

In view of the significant anticipated cost of this project and upgrade, estimated to be in the $75 million range, the GMWC is considering all possible construction and delivery models whether they be in terms of P3, design/build, or standard bid and construction approaches.

Composting facility

The GMWC will soon bring online an advanced biological wastewater treatment process capable of very high solid removal rates. By-products of wastewater treatment, also referred to as biosolids, are now fully used within the large composting operation producing a Type “AA” quality product. The GMWC must ensure that its composting system is sustainable, considering the increased volumes of byproducts that are expected. In 2012, the GMWC awarded a contract for the construction of an Operations Centre which provides staff facilities, equipment bays and heavy equipment maintenance capability. This project was completed and turned over to the GMWC in 2014.

In late 2013, the GMWC also awarded a contract for construction of a third compost pad. This will bring the overall processing capacity close to 30,000 tonnes per year or close to 15,000 tonnes of biosolids, considering year-round continuous operation. This phase will be completed in 2014 and provides additional compost production capabilities in preparation for the additional sludge volume to be generated by the proposed advanced biological treatment process. The GMWC plans to continue gradually adding processing and curing capacity over the next few years until the project is fully completed.

© GMWC, 2014. All rights reserved.