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Wastewater treatment in itself can have many ups and downs on a daily or weekly basis. So many things can impact how successful the wastewater process is at removing the critical components of BOD, TSS and nutrients.
Fall can be even harder to control the process sometimes than winter. At least in winter it gets cold and colder so you can prepare for the inevitable, but in fall, it can be 70 degrees one day and drop down to 40 the next. These wide swings make it very hard for the bacteria to adjust to the temperature changes. Remember, temperature is one of the "Critical 5 " components in a wastewater treatment plant. Temperature can significant impact whether you are winning the time and numbers game. Remember, wastewater treatment is always a time and numbers game. Since you really are limited by the time component- (in reality due to the size of the treatment plant) the only thing you can play with is the numbers factor. That means adjusting the numbers of bacteria or MLSS in the aeration basin. How do you adjust for such major swings? Another thing that may impact the plant in the fall, are the cold rains that sometimes can increase the flow to the plant. Hurricane season is also in the fall. Plants situated down in the south or along the coasts have to keep this in mind also.
Another thing to consider, for every ten-degree change in the weather, the bacteria lose one logs growth of activity. If your outside weather drops 20 to 30 degrees in one day, that can significantly impact the activity in your system, if you do not have an influent with high temperatures consistently like many industrial plants do. That means you have to adjust the amount of RAS and WAS in your system to reflect the temperature changes. Well, you can only adjust the MLSS as quickly as your pumping capabilities allow. Another thing to remember, the bacteria are finicky. They do not like significant changes. Any time a change of more than 10 percent is made, on any variable that is critical to them, they get temperamental. Let's walk through a couple of plants and where in the process they might have problems. The biggest problem areas are going to be where the plant is exposed to nature.
Let's start with a Lift station or Wet well if you are a municipality. Some lift stations have tons of grease sent to them, especially with the increase of strip malls and restaurants. Two things can happen in the lift stations with colder weather. The grease can harden with colder temperatures and start to form "turtles". These can clog up lines and cause problems with pumps, but are a bit easier to get out of the primaries. Biological products can be added to the lift stations to help with grease degradation. The second thing is that fall rains can cause grease to break off from the grease shelf in the lift stations or on rims along the pipes and send an overload of BOD to the wastewater treatment plant. High Grease can increase the growth of Nocardia and Microthrix parvicella and cause serious foaming problems. Watch what happens in your primaries during high rains. If you have manual skimmers, make sure to clean out the grease 2-3 times a day and do not allow it to build up.
If your plant mixes storm water run off that gets routed through the wastewater plant, many times oil can drip on the pavement or parking lots. This gets washed off during high rains, ends up in the system and down to the wastewater plant. You will see the colorful rainbow sheen on the surface. A normal primary clarifier will not capture this, only API's or DAF's will take this out of the system. This can be a problem because these types of oils will also cause the growth of Nocardia and Microthrix in the aeration basins. Some plants perform major shutdowns, and clean-ups of machinery in the fall or winter when business slows down. Leaky oil from machinery that can get into the system can also cause the same problems.
Another thing to keep an eye on in the Primary Clarifiers is the solids. Make sure to check the bed levels and adjust the speed of the rakes if necessary. Floating solids indicate that the primary is holding solids too long. This can generate septic conditions that again, can promote the growth of other types of filaments in the aeration basins.
Aeration Basins have issues of their own. With the wide swings in temperatures during the day and then in the evenings, vs. just the wide swings that can occur day to day in the fall, sludge age is critical to watch. Use the microscope daily. Many plants use a "fixed" number for MLSS and for the depth of bed in a clarifier. This is the wrong way to run your plant. If you get hit with a high loading of food, and you have 1 foot of solids and the bacteria are in a high growth phase, you are wasting the bacteria that are critical at this time to consume the food. Maybe for a few days, you need two t  o
three feet? Look under the microscope, if you have a ton of amoebae and
flagellates, it is young and you are losing the time and numbers game. On the
other hand, if the temperature is warmer, there has been no rain, the flows are
slowed down, you may have a very old sludge age, and you have rotifers and worms
in the system. You need to increase your wasting in spite of what your "normal"
standards are. The point is, there is never anything "normal in a wastewater
plant. It always changes, and you may need to make minor changes daily if you
want to keep winning the time and numbers game. Use your microscope, the
bacteria will tell you what direction you are headed in. Remember that they can
look completely different in 24 hours! Their life span is only 20 minutes to 2
hours, so if they get hit with a spike of food, they will change quickly!
One way to help with the TSS and ashing is the use on spray nozzles with effluent water. This can help temporarily knock down some of the TSS and cut costs or eliminate the use of polymers in the clarifier. Some plants only use a spray on the centerwell, some have a spray attached to the rakes, so that the sprays hit the entire clarifier periodically.
Digestors also need to be considered. Temperature is a critical component in
digestion. Make sure to watch the pH also in the system. These are two variables
that are often overlooked in both anaerobic and aerobic digestion.
What are some additional ways to help with weather changes? Upset Recovery Programs- Some plants keep a small amount of bacterial products on hand for upset conditions. Temperature swings can impact a plant if the weather changes significantly. Loading swings can also impact the plant more in the fall and winter months. For many industrial plants, if a significantly high loading comes through the plant, bioaugmentation can be used to instantly get the plant up to speed and beat the time and numbers game without delay or impact to the final effluent quality. Since many plants can only return so much RAS to the front end and are limited by pumping speed, or even the amount of bacteria in the current system, the use of biological products is a quick and easy way to help increase the activity instantly. Remember it does not take a ton of product to instantly bump up the system. A typical maintenance dosage is only 1 lb of product for every 1MGD a day if the typical flow is around 2-300 parts of BOD. You can do the math, if your flow is lower, but the BOD higher make adjustments. See our Math calculations where in 24 hours 6.7 lbs of product equal the equivalent of trucking in a 4000 gallons of MLSS from the neighboring plant! Sometimes being prepared for an upset is better than waiting for it to happen and scrambling. The bacteria products usually have a pretty long shelf life- 6 months to a year, so having a small amount on hand can be a good idea if your plant has the potential for upset conditions or wide swings in influent loading. Biofeeders for the use of bioaugmentation in Papermills
What are biofeeders and why would a plant want to use them. Since wastewater in the winter months more than any time is a time and numbers game, it may be hard to increase the numbers cost effectively. It would be cost prohibitive to have to add 40-60 lbs of product a day to the system. In these cases, a biofeeder can be used to "grow up" the bacteria and increase the numbers. With the use of a biofeeder and 18-24 hours grow up, 10 lbs of bacteria can be the equivalent of 100 lbs. Now, the cost of a program is significantly more realistic and an acceptable way to help reduce BOD in a plant. Dual programs with Bacterial supplements and micronutrients can also significantly cut back on the dosage of product required to help meet discharge permits. The correct amount of nutrients as well as micronutrients can make or break a bacterial program.
Lagoons-Winter BOD issues and bioaugmentation Bioaugmentation in once through lagoons can significantly impact not only BOD and TSS in the final effluent, but a properly designed program can help lower solids generation in lagoons that lead to costly dredging. Troubleshooting Lagoon Systems Total System Optimization- Case History Wild Weather-Impact on a wastewater treatment plant Hurricane or Severe Weather Upset recovery program Contact Environmental Leverage Inc. if you need help with your plant on some of these issues!!
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Wastewater
in the Fall- Problems and Solutions
Fall
and Winter with their fluctuating temperature changes can have a significant
impact on the wastewater treatment process. 
Clarifiers
are another area that can significantly be impacted with fall and
winter weather. The temperature changes can easily cause turnover in a clarifier
and make the entire bed float. See our newsletter on
More
on Lagoons and weather issues