Comox Valley Wastewater Treatment Facility Upgrades:Biological Nutrient Recovery and Biogas Production

Group B5: Xrystos Bhegani, Luke Privett, Anand Samra, Marisa Tellis, Ariel Zheng

Introduction

Raw Sewage

Mechanical Screening

Grit Removal

Grit

Primary Clarification

SecondaryTreatmentAeration

Secondary Clarification

Biological Nutrient Recovery System

System Effluent

-TSS reduced by 98%-BOD reduced by 95%-P reduced by 99%-N reduced by 90%

Retrofitted System UpgradesExisting Treatment ProcessExisting Treatment Process

SludgeThickening

Water Recycle

Water Recycle

Water Recycle

Sludge Recycle

SludgeBlending

The Comox Valley is a growing community on northern Vancouver Island surrounded by breathtaking nature and a thriving ecosystem. The residents of the Comox Valley take pride

in the surrounding environment and are passionate to maintain its integrity. The Comox Valley Water Pollution Control Centre (CVWPCC) treats the wastewater of a majority of the

population which includes over 44,000 residents. The objective of this capstone project is to use the technology of biological and chemical engineering to provide a series of

upgrades to assist the CVWPCC in maintaining the environment as the community continues to expand in the years to come. These upgrades go above and beyond what is expected

from a wastewater treatment plant and include a Biological Nutrient Removal (BNR) system and a Sludge Digestion System. The BNR system employs both biological nitrogen (N)

removal and enhanced biological phosphorus (P) removal to lower the nutrients of the system effluent with the ultimate goal of water reclamation. The sludge digestion system

utilizes the nutrient rich sludge to create biogas used to power the plant and fertilizer sold to the local community to offset the energy and cost requirements of the plant. .

Plant Layout & Location

A very special thanks to Zoe Berkey, the engineer at the CVWPCC that helped make this project possible; to all the other

engineers at the CVWPCC who provided input to this project; to Josh Torry and the other operators who helped facilitate

a tour of the centre; to Mr. Sergio Beretta who provided a tremendous amount of inputs for our process diagrams; and

our instructors and assistants Dr. Jonathon Verret, Lee Rippon, and Dr Sue Baldwin.

AcknowledgmentsSludge trucked toComposting Facility

Blended SludgeDewatering

N itrogen Removal P hosphorus Removal

1) Nitrification: the ammonia (NH4) is oxidized to nitrite

(NO2-) by Nitrosomonas then to oxidized to nitrate (NO3

-) by

Nitrobacter ; occurs under Aerated conditions

NH4 + + O2 → NO2- + H2O + H+

NO2- + O2 → NO3

-

2) Denitrification: the nitrates are reduced to nitrogen gas

(N2) by Pseudomonas ; occurs under Anoxic conditions

NO3- + H+ → N2 + H2O

A high flow rate recycle line from the Aerated zone to the

Anoxic zone allows the system achieve ammonia < 0.5mg/L

and nitrate <2mg/L

P removal is made possible by the incredible ability of

phosphate accumulating organisms (PAOs). PAOs are able

to store more polyphosphate than required for growth.

Anaerobic conditions: PAOs use stored polyphosphates,

release phosphorus, consume organics, and store energy.

Aerated conditions: PAOs use stored energy to uptake

phosphorus, store polyphosphates, and grow.

Anaerobic Digestor

Screw Press

Pre-Anoxic Anaerobic Anoxic Aerated

The Johannesburg ConfigurationIncludes the standard Anaerobic, Anoxic, and Aerated zones, necessary for N and P removal with the addition

of the Pre-Anoxic zone. Nitrates present in returned sludge disrupt Anaerobic conditions, reducing energy

stored by PAOs reducing their ability to reabsorb P in the Aerated zone. The Pre-Anoxic zone removes these

nitrates improving the removal of both N and P. With proven to be success operating in colder climates and

with dilute wastewater this was the best option to ensure our system maintains nutrient removal year round.

Why Thermal Hydrolysis?

● Increases the amount of biogas produced

by 50% by accelerating the solubilization

of particulate organic matter

● Operates at elevated temperatures,

reducing potential pathogens present in

wastewater

On-Site Sludge Digestion System

Biogas

CAPEX

92MOPEX

4.7M

Water Recycle

Water Recycle

Fertilizer

Equipment20.9%

Installation8.2%

Instrumentation, Piping & Electrical

11.3%

Building & Service Facilities17.6%

Yard Improvements

2.1%

Engineering & Construction

13.8%

Contractors Fee3.7%

Contingency7.4%

Working Capital15.0%

Raw Materials3.8%

Labour12.7%

Utilities6.2%

Maintenance & Supplies

38.0%

Laboratory Charges

2.2%

Insurance11.6%

Plant Overhead

10.0%

General Expenses

6.0%

Biogas Upgrading

9.6%

PAOsPAOs

Organics P

EnergyStorage

Poly PEnergyStorage

PP

Poly P

P

Growth

Anaerobic Conditions Aerated Conditions

PAOsPAOs

Organics P

EnergyStorage

Poly PEnergyStorage

PP

Poly P

P

Growth

Anaerobic Conditions Aerated Conditions

Environmental Benefits

Economic Breakdown

Advantages of using high-rate continuously fed stirred anaerobic digesters:

● Good mixing results in no stratification or loss of capacity due to supernatant, scum, or dead pockets

● Continuous addition of raw sludge and using thickened sludge results in a significant reduction of retention times

● Achieves 50% destruction of volatile solids allowing the digestate to be used in

fertilizer applications

Benefits of the Screw Press over

other dewatering equipment

● 70% reduced energy consumption

● 90% reduced water consumption

● Low operator attention

● No noise or vibrations

Thermal Hydrolysis

Reactor

Thermal Hydrolysis

Reactor

Victoria

VancouverComox Valley

Victoria

VancouverComox Valley

Thermal Hydrolysis

ReactorAnaerobic Digester

Digestate Dewatering

BNR System

Supporting pumps and heat

exchangers

Primary Clarifiers

Aerated Basins

Sludge Thickening

Secondary Clarifiers

Produced by biogas reducing demand of fossil fuels

Energy Production

72000GJ/year

By displacing the production of artificial fertilizers

Reduced CO2 Emissions

-175 tonnes/day

CO2

Reduced CO2 Emissions

-175 tonnes/day

CO2

By displacing the production of artificial fertilizers

Reduced CO2 Emissions

-175 tonnes/day

CO2

Nutrient removal is a step towards additional applications for water reclamation, reducing

the communities water consumption

Water ReclamationWater Reclamation

Nutrient removal is a step towards additional applications for water reclamation, reducing

the communities water consumption

Water Reclamation

BNR system replaces

the aerated basin

No need to truck

sludge with on-site

processing!