As society’s waste stream grows larger and more complex, preservation of public health and the environment requires thoughtful innovation in wastewater engineering and treatment processes. Hazen and Sawyer has long been at the forefront of this innovation, maintaining the industry’s top expertise in biological nutrient removal, high-rate disinfection, and advanced membrane processes, as well as traditional primary and secondary wastewater treatment.

After extreme flooding in the Cumberland River (TN) basin inundated the Clarksville Wastewater Treatment Plant, Clarksville Gas & Water hired Hazen and Sawyer to design and manage construction of the restoration of treatment operations, rebuilding a state-of-the-art facility with more efficient treatment operations and increased wet weather capacity.

For the 30-mgd Nansemond WWTP, we designed a plant expansion and upgrade that will meet an ammonia limit of 2 mg/L and a total nitrogen limit of 10 mg/L year-round.

In a pilot test in Hollywood (FL), we developed a treatment approach that minimized the need for reverse osmosis treatment that is typically used for indirect potable reuse, potentially greatly reducing capital and operating costs.

As a part of the Santo Domingo Sanitary Sewer Master Plan Study, we conducted a series of oceanographic studies in the Caribbean Ocean to assess the feasibility of installing several ocean outfalls in the coastal region of Santo Domingo.

Hazen and Sawyer piloted Electrocell™ technology at the North Regional Wastewater Treatment Plant to evaluate the suitability and effectiveness of the treatment unit for nutrient removal and pathogen reduction on anaerobically digested biosolids.

A Hazen and Sawyer study revealed that, using the appropriate equipment, the Cape Fear Public Utility Authority’ 16-mgd James A. Loughlin, Jr., WWTP could turn digester gas into electrical energy at a profit - creating $2.40 of present value with each dollar of invested capital – while simultaneously reducing greenhouse gases by tapping a readily available renewable energy resource.

To address struvite issues and a stringent phosphorus limit (0.08 mg/L) at F. Wayne Hill Water Resources Center, Gwinnett County undertook a pilot program and business case evaluation to assess the potential for a nutrient recovery process that treats phosphorus and ammonia while producing marketable fertilizer as a by-product.

Johannesburg Water is upgrading the sludge handling and digestion facilities at its five wastewater treatment plants. The new high-performance digestion facilities will significantly offset energy costs at the plants – as much as 55% at one plant.

Improvements to the Neuse River facility included a new equalization basin to handle wet weather flows, facilities for total nitrogen removal, a sludge management plan, and conversion of the existing chlorine contact tanks to ultraviolet disinfection contractors.

In anticipation of required nutrient reduction, Broward County undertook a pilot program to evaluate cost effective process modifications that would achieve the necessary reductions at the North Regional Wastewater Treatment Plant.

For New York City, the project team assessed the vulnerability of infrastructure and prepared recommendations for the study drainage area and select wastewater treatment facilities. The team also defined adaptation recommendations for all WWTPs and pump stations at risk of inundation during extreme storm surges.

As part of the Port of Miami recently provided fast-track design-build services to replace underwater pipelines to prepare for the dredging of the Port of Miami access channels to accommodate “New Panamax” ships allowed by the deepened Panama Canal.

Hazen and Sawyer performed asset management assessments of two 72 mgd WWTPs in Nassau County (NY) under an aggressive 90 day schedule.

A 5-stage biological phosphorus-nitrogen removal (BNR) process was determined to be the most cost-effective, involving lower capital and operations and maintenance costs for the North and South Durham Water Reclamation Facilities.

We have helped clients develop new, technologically-advanced wastewater treatment plants from less than one to more than 300 million gallons per day (mgd) capacity, each uniquely designed and built to meet specific desired outcomes. Just as often, we have assisted in the rehabilitation, upgrading, and expansion of existing plants. Our engineers are skilled in maximizing the use of existing structures and equipment and our careful project sequencing keeps plants in service during the phase-in of new facilities.

Through decades of experience assisting numerous treatment plants through various levels of upgrades, we have developed a state-of-the-art, site-specific approach to process modeling, design, and optimization using the BioWin™ simulator. Our extensive modeling library enables us to identify the most appropriate technology to meet any individual plant’s needs, accounting for process optimization, regulatory compliance, and energy efficiency.

Our approach also includes expert analysis and optimization of secondary clarifier performance using the 2Dc model – a state-of-the-art quasi-three-dimensional Computational Fluid Dynamics (CFD) model that can be used for circular or rectangular clarifiers. We also employ Life Cycle Analysis (LCA) and Total Cost Accounting (TCA) to assess both the internal costs (those borne by the utility) and external costs (those borne by society) of different design options, enabling decision-makers to consider each.

Hazen and Sawyer has also planned, designed and managed the construction of numerous sludge management facilities for both new and upgraded plants. These facilities range from lagoons to advanced highsolids sludge dewatering systems that yield the greatest possible disposal efficiency of plant residuals. Effluent, residuals and biosolids can often become an asset through any number of beneficial reuse options. From vast agricultural irrigation systems, energy generation facilities and aquifer recharge fed by treated wastewater, to fertilizer production from treated sludge, these reclamation and reuse projects can address both resource demands and market potential.