Laserfiche WebLink
BioFiltrat on Process <br /> (oxidize) organic products or carbon. These organisms reduce the BODS(food) <br /> or carbon BOD in the wastewater. Autotrophic bacteria will use (oxidize) <br /> inorganic compounds such as the various forms of nitrogen. The overall <br /> simplified biochemical reaction in biofiltration is as follows: <br /> inert matter+organic matter+oxygen+ = new organisms+carbon dioxide+water+ <br /> nutrients+microorganisms inert matter <br /> As described above, with proper operation these reactions will stabilize <br /> waste. The end products are new organisml}, water, carbon dioxide and inert <br /> matter. The key to the above equation is new organism growth. To <br /> suecess£ully remove waste from water, as the equation above shows, the ` <br /> operation must deal with the excess population of organisms. For this <br /> reason, basic facility design includes waste sludge storage and digestion unit <br /> processes. <br /> BOD and Biofiltration Growth <br /> Biochemical Oxygen Demand (BOD) is a test method to determine how much <br /> a known volume of water will deplete dissolved oxygen. Often BOD is <br /> implied as oxygen demand. BOD is used to provide a relative measure of the <br /> amount of food material available to a biological system (the raw sewage <br /> value). <br /> To remove BOD in the treatment plant, new organism growth must occur. <br /> Operation at this point becomes crucial. Not paying attention to the new <br /> growth will result in a sludge that is starving for food (BOD). Sludge <br /> settleability suffers to the point where sludge is lost over the weir and <br /> effluent quality is poor. There is a specific balance between sludge quantity, <br /> sludge growth and the amount of food (BOD) entering the plant. Generally, <br /> 0.5 lbs. of sludge is produced per 1.0 lbs. of BOD applied. The balance point <br /> is where the growth rate equals the die off or waste rate. Even if the plant is <br /> balanced, sludge wasting is still required because dead cells, new cells and <br /> trash continually need to be removed. <br /> The Nitrogen Cycle in BioFiltration <br /> The four forms of nitrogen occurring in wastewater are Organic Nitrogen, <br /> Ammonia Nitrogen ( 4113-N), Nitrite Nitrogen (NO2-N), and Nitrate Nitrogen <br /> (NO3-N). Raw wastewater (influent) is primarily organic and ammonia <br /> nitrogen (NH3): 40% organic nitrogen and 60% ammonia nitrogen. In the <br /> presence of dissolved oxygen (greater than 1.0 mg/1) and adequate time (SRT <br /> 10 to 15 days), nitrifying bacteria (nitrifiers) will grow. The first group of <br /> 7H Technical Services Group Operation &Maintenance Manual <br /> BioFiltration Process Page 9 of 26 <br /> Rev991215 <br />