Atkins is leading the overall program for the seventh addition of improvements to the Little Patuxent water reclamation plant in Howard County, Maryland, including designing improvements to expand treatment capacity to 29 million gallons/day, improving treatment performance to achieve enhanced nutrient removal, and treating a significant organic waste load from a large industrial client.

To accommodate the industrial waste load, Atkins evaluated a variety of anaerobic and aerobic processes. A low-rate anaerobic contact process, followed by an aerobic selector process, was installed for its ability to produce the highest quality effluent. This process is protective of the existing biological nutrient removal (BNR) process and is the overall lowest cost option. A slip­stream of the industrial organic waste will be used to create volatile fatty acids, which will enhance the existing biological phosphorus and nitrogen removal processes. Odors from the aerobic and dissolved air flotation processes will be sent to a new modular biofilter odor control system. To save time, the new pretreatment facilities were delivered by a combination of construction manager-at-risk (CMAR) and design-build delivery methods. We assisted Howard County with procurement and selection documents for each alternative delivery process. Innovative uses of existing facilities saved the County more than $5 million.

Atkins evaluated both post-anoxic zones and denitrification filters; denitrification filters were chosen, and Atkins assisted the County in pre-selection of the filter manufacturer. Other improvements include new bar screens, expansion of the existing BNR Johannesburg process, new secondary clarifiers, an intermediate pumping station to send flow to the denitrification filters, and a new ultraviolet disinfection system. Solids processing improvements include a new centrifuge and improved odor control and collection facilities, with an acid scrubber for removal of ammonia released from the high-lime stabilization process. To expedite the construction and reduce overall risk, the main BNR and expansion contract is also being delivered CMAR. Atkins assisted the County in recommending the alternative delivery approach, and worked with the County to develop the request for qualifications and request for proposals.

• Construction services
• Program management

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