Wastewater Treatment is the process of removing contaminants from wastewater. The objective is to improve the wastewater quality to a point where it may be reused or disposed of without detrimental environmental impacts. The process of removing contaminants involves physical and biological processes and produces residuals and biosolids which must be managed. ABL staff members have provided engineering expertise to design wastewater treatment plants for federal, municipal, commercial and industrial clients using a variety of physical and biological methods including lagoons, sequencing batch reactors, activated sludge, rotating biological contactors, trickling filters and other fixed film bioreactors, clarifiers, dissolved air flotation, anaerobic and aerobic digesters, sludge dewatering and chemical/physical treatments. All designs were preceded with predesign studies to define concepts and budgets.
 
Activated Sludge systems use suspended natural biological and bacterial growth to remove contaminants. The wastewater is mixed with a bacterial floc in an aeration tank where the contaminants are removed by sorption and subsequent breakdown. The bacterial floc pass with the wastewater into a clarifier where the floc settles and the treated effluent is produced. Some of these plants have included pretreatment processes, sludge digestion and dewatering processes, effluent filtration and disinfection. Extended aeration activated sludge processes have been designed for Greenwood, an industrial client, and Michelin North America Ltd.
 
Lagoons are large, low rate, suspended growth treatment systems. These systems have a lower operator skill level and lower operating cost than many other treatment systems. They require a large site. Lagoon systems often produce effluent which has higher than acceptable SS due to growth of natural algae. This sometimes necessitates that the effluent be filtered before disinfection processes or release to the receiving water. Lagoon systems have been designed for the Town of Antigonish, Fox Harbour Developments, Sunset Residential Centre, and Tim Horton's Children's Camp.
 
Fixed Film Reactors utilize films of attached bacteria to treat the wastewater. ABL staff have investigated and designed fixed film processes including trickling filters, rotating biological contactors (RBC) and innovative rolling bed hybrid reactors. The 'Lunenburg Process' was developed by ABL specifically to meet the needs of coastal communities with combined sewer systems, and was chosen by the Town of Lunenburg as the most appropriate technology for this historic site.
 
Sequencing Batch Reactors (SBR) are a special form of activated sludge treatment in which all of the treatment process takes place in the reactor tank and clarifiers are not required. This process treats the wastewater in batch mode and each batch is sequenced through a series of treatment stages. ABL has developed our own version of the SBR which is marketed as the ABL-SBR. We have designed SBRs with installed capacities ranging up to 3 MGD (11,500 m³/d). Project examples include: Marine Atlantic Digby, Brudenell Resort, Avonport, Keltic Lodge, a commercial mall, DND Canada, Brookfield, Lunenburg, Baddeck, Pomquet, and Pugwash, Nova Scotia.
 
Industrial Wastewater is unique to each industry. The processes used to treat industrial wastewater are basically the same as those for municipal wastewater but attention must be paid to the qualities of the wastewater, nutrient balance, temperature and other factors which affect the treatment process and equipment selection. ABL has designed wastewater treatment plants including physical chemical treatment and biological treatment. We have experience dealing with wastewaters from airport glycol deicing, oily bilges, metal plating, dairies, apple processing, slaughterhouses and rendering plants, and with landfill leachates, fire fighter training and tire fire wastewater, and fish culture wastewater.
 
Commercial and Resort Wastewater has been treated at Keltic Lodge, Brudenell Resort, Sonesta Beach and Palmetto Beach Resorts, Bermuda, and a commercial mall using ABL-SBR. ABL has applied Biopyramid Greenhouse technology to the post treatment of wastewater from a 14 unit apartment building complex and consistently achieved effluent averages of about 5 mg/l BOD and SS. Other commercial clients include a children's camp, a marine ferry terminal, an environmental health clinic and recreational centres.
 
Treatability Studies are not typically required for municipal wastewater but industrial wastewater treatment may benefit from bench and pilot studies. ABL has laboratory facilities and pilot plant equipment which can be mobilized to the client's site to perform treatability studies. These studies are essential to ensure that treatment concepts and design parameters are properly selected. We have performed these studies for DND Canada, a rendering plant, and industrial clients (for glycol and fish processing effluents, for example) in the design of their treatment facilities.
 
Odour Control system design has been provided at many plants including Eastern Passage Sewage Treatment Plant and Chester Sewage Treatment Plant. System design considerations included containment, capture, treatment and dispersion.
 
Biosolids are generated by the growth of bacteria as contaminants from the wastewater are consumed. These bacteria accumulate in the treatment plant and must be managed if optimum wastewater treatment is to be achieved. ABL staff have designed management systems for wastewater sludges including aerobic and anaerobic digestion, dewatering and disposal. Services have been provided to develop sludge management plans and to maintain and develop facilities. Projects have included ongoing maintenance dredging of the Aerotech sludge lagoons which serve Halifax Regional Municipality, design of digestion and dewatering facilities at Greenwood, septage receiving stations, sludge/septage treatment facilities, and dissolved air flotation.
 
On-site Systems include disposal beds and packaged wastewater treatment plants configured to treat and dispose of the wastewater without offsite discharge. Usually the wastewater is percolated into the soil through infiltration beds or trenches or is disposed by irrigation or other means. ABL has designed systems ranging to 10,000 gpd (38 m³/d) capacity as in the recirculating sand filter installed at Sir John A. MacDonald High School, Hubley, NS. ABL has investigated failures of large systems for clients including the Nova Scotia Department of Public Works and the Municipality of the District of Yarmouth.
 
Wastewater Collection systems have been designed for numerous municipalities including the Municipality of Yarmouth, Town of Lunenburg, Avonport, and Town of Liverpool. These systems have included gravity sewers, forcemains and pump stations with capacities to 3 MGD. Forcemains approaching 20,000 ft length have been designed and built. The Arcadia system included design of three pump stations, 15,000 ft of gravity sewer, and 19,200 ft of forcemain. The Avonport system included 5 pump stations, 19,000 ft of gravity sewer and 6,900 ft of forcemain. The Lunenburg system has included consolidation and interception of all untreated outfalls and construction of pumping facilities to deliver 3 MGD to the new treatment plant. Sewer separation and flow reduction studies have been conducted in Liverpool, Nova Scotia.
 
Stormwater Management and storm sewer designs have been done for the Town of Liverpool to alleviate flooding problems and for Queens Regional Municipality as part of an infrastructure upgrade in the Village of Milton. ABL also has staff trained in Stormwater Management Modeling (SWMM) software.