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Protecting Against Variable Wastewater Loads

Jim Kang, Ph.D., PE
CDM Smith industrial water expert Jim Kang examines the challenge of variable wastewater loads and flows and an innovative low-footprint solution.

Companies in a variety of industries face pressure to reduce water use at their facilities. As they strive to cut down fresh water consumption, recycling and reusing process water continues to garner interest as a way to achieve sustain­abil­ity goals. And for companies that are manu­fac­tur­ing multiple unique products at their facilities, distinct variable wastewater flows challenge the notion of water reuse. To improve treatment efficiency and avoid overloading their treatment systems with these varying loads, facility managers are seeking a reliable solution that keeps the possibility of water reuse on the table. 

Pro­duc­tion Line Chal­lenges
In the past, industrial wastewater treatment facilities were designed as fixed systems based on projected wastewater loads. Today, these aging facilities cannot take the same approach because of flow and load fluctuations. Many facilities are implementing wastewater treatment tech­nolo­gies like anaerobic digestion to meet their energy recovery and water reuse objectives. However, industrial wastewater treatment has become increas­ingly difficult as corpo­ra­tions produce a larger variety of products to meet evolving consumer preferences. As Kang explains, “Food and beverage manu­fac­tur­ing facilities may change their production line multiple times per day. This generates drastic organic highs and organic lows, coupled with pH swings in the wastewater, straining the water treatment system and related downstream treatment systems.”

In addition, facilities must implement clean-in-place practices between batches when producing separate products. They allow facilities to clean equipment without disas­sem­bling machinery, but require water and chemicals to clean systems between loads. Every new batch going to production could use different ingredients and produce completely different waste constituents. This constant change leads to a constant cleaning of the vessel.” For example, a food and beverage facility producing 10 to 20 beverages a day may create products ranging from high sugar energy drinks to vitamin enhanced products, requiring a thorough cleaning between each batch.

Facilities must carefully navigate these obstacles to maintain operations and avoid plant disruptions. When wastewater treatment systems become overloaded, the bacteria used to anaer­o­bi­cally digest organic material die and get washed out. These special bacteria are expensive to purchase and require close care. “Bacteria wash-out causes complete system shut downs and disruptions, requiring facilities to regrow their biological processes using new bacteria,” explains Kang. Addi­tion­ally, bacteria wash-out may lead to regulatory violations. “Industrial wastewater treatment plants have categorical discharge limitations based on the types of the industry and manu­fac­tur­ing processes. If they cannot handle bacteria wash-out or the varying loads of pollutants in the wastewater, they will exceed these limitations and face hefty surcharges.”

Every new batch going to production could use different ingredients and produce completely different waste constituents.
Jim Kang, CDM Smith vice president, Industrial water expert 

Main­tain­ing Op­er­a­tions with Moving Bed Biofilm Reactors
A universal challenge for industrial facilities is dealing with site constraints. Fortunately for facility managers combating the strain variable wastewater loads place on their treatment systems, many new innovative tech­nolo­gies are reasonably compact. One example, moving bed biofilm reactors (MBBR), can be retrofitted to existing facilities for a more robust, stable and reliable system. This type of reactor can increase treatment capacity and sustain the impact hydraulic and organic loads have on the digester.

MBBR is an effective biological treatment process that uses attached-growth moving biocarriers. The bacteria reside in biocarrier media that provide extra surface area (at 150 square feet per cubic foot of media) for bacteria to grow on. MBBR’s honeycomb shaped biocarriers help retain the microor­gan­isms and prevent them from washing out. The bacteria grow on these carriers, which have a slightly lighter density than water and are kept in movement with wastewater inside a reactor. The movement inside an MBBR can be caused by aeration in an aerobic reactor or by a mechanical mixer in an anoxic or anaerobic reactor. It has been proven that MBBR systems have higher biomass, higher organic loading capacity, higher tolerance to loading impacts and a smaller footprint when compared to conven­tional activated sludge treatment systems.

Therefore, MBBR provides operators and plant managers with an additional, robust mechanism to handle hydraulic and organic load variations by providing additional treatment capacity with a healthy bacteria population. “What really keeps plant managers awake at night is the reliability of their system,” says Kang “Adding MBBR technology would solve this challenging issue without requiring expansion of your treatment plant.”


CDM Smith vice president Jim Kang brings nearly 30 years of experience in water and wastewater treatment, technology development, soil and groundwater remediation system design, and operations and maintenance.
r. Jim Kang brings nearly 30 years of experience in water and wastewater treatment, technology development, soil and groundwater remediation system design, and operations and maintenance.Dr. Jim Kang brings nearly 30 years of experience in water and wastewater treatment, technology development, soil and groundwater remediation system design, and operations and maintenance.

Jim Kang Jim Kang
What really keeps plant managers awake at night is the reliability of their system. 
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