Industrial Wastewater Treatment: Targeted Solutions with MBBR Media (Chemical/Textile/Food Processing)

There is no standardized industrial wastewater. A chemical plant can discharge water containing strong solvents, whereas a textile factory has to work with dyes which are difficult to dissolve. Food processing plants, however, have been known to generate wastewater that is usually rich in organic wastes and fats. Treatment is a challenge due to such differences. MBBR Biochip Media provides an adaptable means of managing these fluctuating environments by aiding the increase of beneficial bacteria within the system. It can be used to treat water more steadily with the right set up and maintain the treatment process more stable when water quality fluctuates day-by-day.

Pain Points of Industrial Wastewater: Special Requirements for Media Under High COD/High Ammonia Nitrogen

High COD and high ammonia nitrogen wastewater introduces a series of issues, which are difficult to overlook in actual plants. The water tends to be dark, turbulent and not very strong every shift. In a textile dyeing laboratory, e.g. a batch of textile dye can include heavy dye and surfactants and a batch of cleaning chemicals. Immediate spikes may occur in a food processing plant due to peaks in production and cause COD to surpass normal levels. In the case of treatment systems, such a load causes the biology within the tank to be under continuous pressure. The primary problem begins with the demand of oxygen. High COD implies that bacteria require a lot of oxygen to decompose organics. Meanwhile, high ammonia nitrogen requires nitrifying bacteria which grow more slowly and are more delicate. The presence of the two leads to competition as they vie in order to occupy space and to access oxygen. Unbalanced system often results in a slowing of ammonia removal initially and unstable effluent quality. MBBR systems are based on the use of carriers to carry biofilm, although not every condition is conducive to stable growth. The media should be able to sustain thick and active biofilm in high-strength wastewater, but not easily peel off. Simultaneously, it must have sufficient surface area to allow co-existence of fast-growing heterotrophic bacteria and slow nitrifiers. When the surface is excessively smooth, biofilm is not able to adhere. In case it becomes very thick, oxygen cannot penetrate the inner layer and the bacteria within it may perish. Similar spikes of ammonia were recurrently reported by operators of a chemical plant in Batangas despite the addition of aeration. It was not just air supply but also the uneven growth of biofilm within the tank. Once the mixing was enhanced and the acclimation period was extended, the system was more stable since the biomass was given time to acclimate to toxic peaks. In real operation, constant loading is important as opposed to rapid repairs. The biofilm can be shocked by sudden alterations of flow or chemical dosing. Having a smoother feed, high but not violent aeration and allowing the system time to adapt all contribute to the media performing better in the harsh conditions.

Chemical Wastewater: Corrosion-Resistant MBBR Media Selection & Process Optimization

Chemical wastewater creates a different type of stress on biology than many other industries do. The wastewater normally contains acids, alkalis, solvents or cleaning agents that can eat away at equipment and biology over time. Some facilities will even experience swings from very low to very high PH throughout a single production cycle. This makes it difficult for bacteria to stay active and for the carrier media to provide a stable surface for the biofilm to attach to overtime. Corrosion and chemical attack are huge factors when deciding on what type of MBBR media to use for chemical wastewater. The majority of plants will lean towards high-density polyethylene (HDPE) carriers because of their ability to withstand harsh environments. Surface composition of the media also plays a part in this. A rough, but stable surface allows for biofilm to attach quickly even during times where the system is exposed to fluctuating chemicals. As the media's surface begins to break down or become brittle over time, the biofilm layer will lose its grasp and ability to be treated will diminish. Operators at a small coatings production facility were experiencing repeated bouts of diminished COD removal efficiency. After studying the problem they realized that it was due to uneven biofilm growth after solvent-rich discharge spikes. During these times the media inside the reactor was unable to provide a consistent medium for biofilm to grow on. Not only did the facility switch over to a more chemical-resistant carrier, but they smoothed the shock load before it reached the biology. This was done by implementing an equalization tank before the MBBR basin. Equalization tanks are one method of process control that can help with chemical wastewater. They enable a blending of different wastewater lots before they reach the biological stage, which stops large chemical doses from rushing through. pH control is another important factor to consider. By keeping the pH within a certain range, your nitrifying bacteria will be able to last longer and recover faster from shock events. Aeration must also be dialed in when dealing with chemicals. Too much air will sheer biofilm off the media and too much oxygen will slow down the recovery process after a chemical attack. Properly adjusted airflow will keep your system running smoothly without killing off your attached growth. Handling chemical wastewater successfully usually comes down to steady as opposed to sudden control. By having a media that can stand up to the chemicals, and a process that allows your biology to ride out the storms, you give your system the best chance at coping and performing.

Textile/Food Processing Wastewater: Media Application for Efficient Organic Pollutant Degradation

Textile wastewater and food processing wastewater are two very different industries. One thing they have in common though, is that they tend to be very high in organic pollution loads. One may behave differently than others in a wastewater treatment system. Textile wastewater contains compounds such as dye, surfactants and salts that are often refractory to bacterial decomposition. Food processing wastewaters generally lend themselves better to biological treatment, but can be extremely high in COD, fats and suspended solids after peak production periods. MBBR systems rely on biofilm to do most of the work in both applications. The microorganisms are given a place to grow and thrive even if the flow or loading of the system varies due to the media. When dealing with textile wastewaters, one must ensure that you can have a stable biofilm when exposing the bacteria to toxic compounds or heavy colors. Some dye molecules will hinder bacterial activity and as a result you'll need to allow the system some time to establish a healthy microbial population. Once a good biofilm has been established in the media it will slowly start to break down organics and decolorize over time. A denim washing facility in Guangdong was experiencing fluctuations in the color of their effluent. Not only did the wastewater have time to react before being treated, but there was poor biofilm growth present inside the MBBR reactor. After allowing more time for acclimation and having a more stable feed flow, the system began showing improved color removal. Operators even observed that once the biofilm reached a sufficient thickness, the reactor became considerably more resilient to shock loads. Food processing wastewater reacts differently than textile wastewater. A great example would be a dairy facility that pumps wastewater high in fats and protein into the system after cleaning cycles. These organics can cause COD to spike and cause foam formation in aeration tanks. In this scenario, having MBBR media will allow for faster growth of microbes that will consume these organics. Just make sure that the system is mixed properly to avoid fats from building up on one section of the media. Operators at a fruit juice factory noticed clogging taking place at different areas of the carriers due to uneven flow. Not only did the media start to look cleaner, but biofilm activity improved when pre-screening was optimized and aeration patterns were adjusted. When peak production times came, the system ran much more stable than before. Keeping contact between wastewater and active biofilm stable is key in these industries. Consistent loading, no chemical upsets, and time for a biofilm to establish itself will allow the media to work to its fullest potential. This will allow MBBR systems to run under stable conditions with little operator intervention and more predictable results.

Industrial Project Case: Performance Data of MBBR Media in Industrial Wastewater Treatment

For practical industrial use, MBBR media are chosen for their steadiness under varying conditions, rather than solely for their theoretical removal efficiency. Below is a real scenario based on observations from an upgrade of a chemical – textile combined wastewaters treatment facility located in an industrial district in Luzon. Estimated wastewater flow treated in the plant ranges from 800-1000 m3/day. Before upgrading, influent COD would normally range from 1,800 – 3,500 mg/L. Ammonia nitrogen would typically range from 40-85 mg/L. There were instances when the old system would just barely make the required standards, especially on days when the dyeing line and wash lines were both working at full production. A start-up period of 46 weeks was observed after the installation of an MBBR stage with well-established carriers, and tuning up of the aeration system to achieve balance. Biofilms grew slowly but surely throughout the start-up period. Operators avoided drastic changes in airflow rates and kept constant loading as much as possible to allow bacteria to get used to the environment. After reaching stabilized condition, percent COD removal was greater (88-92) with the addition of MBBR technology than with (70) the existing old system. Effluent COD also remained consistently low (<250 mg/L), even during peak influent flow days. The improvement was even more dramatic when it came to ammonia nitrogen. In the old system, readings would usually stay above 20mg/L after treatment. After startup and stabilization, results were able to reach 5-10 mg/L under normal operating conditions with some peak values to strong shock loads. What was remarkable was when one department suddenly doubled their production from the textile line. Influent COD jumped to almost 4,000 mg/L for the duration of 2 days. Instead of having a system crash, the MBBR basin only experienced a slight decrease in performance which recovered within 48-72 hours. Operators noticed that biofilm thickness had increased slightly from before the influent shock load happened, which helped take up some of the load. Maintenance logs also showed a decreased amount of sludge bulking compared to years prior when only the activated sludge process was used. There was more consistency with the amount of excess sludge produced and dewatering became easier. The lesson learned from this case was simple. The media didn't entirely assume control of the treatment. It simply allowed the system more flexibility. Biofilm acted as a cushion…a living cushion that gave operators time to react to changes when loading varies, and kept performance from falling.