How will wild and extreme weather impact  your plant?  What are some of the problems weather can cause?

Weather is unpredictable. Extreme cold or high temperatures, excessive rain, hurricanes, blizzards or drought can all impact the conditions of a wastewater treatment plant.

What are some of the effects and some of the things you can do to combat these types of problems?

Obviously, most plants are designed with these issues considered. Many plants have spare EQ tanks, holding tanks, diversion ponds, heater or heat exchangers for just such occasions.

 Some plants do not and are stuck running around trying to jury rig what ever they can to limp through the sudden weather changes that can impact their plant.

Excessive rain can cause hydraulic washout. This can impact many different parts of a plant.

Hydraulic washout can cause problems in the primaries as well as the aeration basins. Washing out too much of the MLSS from the aeration basin as well as the clarifiers can make your biomass younger. While the carbonaceous bacteria can recover relatively quickly, the nitrifiers, if washed out, will take quite a while to rebuild up a significant amount of numbers capable to handle the plants influent. Waste less if this happens, and try to return more recycle if possible. If you have a once through lagoon, you can reseed with bioaugmentation cultures. Bioaugmentation cultures may be the carbonaceous bacteria, or nitrifiers, if really necessary.

Heavy rains can cause numerous issues just in a lift station for municipalities. Rain on the roads where construction occurs can wash off high levels of oils that cars drip while stuck in traffic waiting for lanes to change. This can cause foaming due to Nocardia and Microthrix, which thrive on excessive oils and grease.

Rain also can cause huge chunks of grease to dislodge in sewer lines and lift stations to make its way down to the primaries of a wastewater treatment plant. Check your primaries, if you have the skimmers that need to be adjusted by hand, make sure you do it more often after high rains to pull out as much grease as possible. Definitely, make sure someone comes in on the weekend if you only normally run 5 days a week to pull the grease off the primaries. Many plants overlook this and build up too much grease on the weekends and come in to the plants on Mondays with many problems.

Both of these conditions can cause foaming in the aeration basin. Try to remove as much of the oil and grease in the primary as possible.

High rains, hurricanes or flooding can cause clarifiers to washout easier than many of the other parts in the system. This can cause the beds to rise and float out over the edge of the clarifier, loosing a critical amount of your MLSS. Clarifier Optimization and troubleshooting

Some plants have an EQ tank, a diversion tank, or empty aeration basins or clarifiers that they can divert some of the excess flow during high rains in order to bleed some of the water back into the system after the high rains have stopped. This is the best case scenario and allows the plant time to recover from the heavy rains, without causing any washout or loss of MLSS and efficiency of the plant. Some plants are not allowed this luxury.

Municipalities and some food plants that have to disinfect prior to discharge are significantly impacted by high rains and hydraulic overload. If the flows are too high and run too fast through the systems, especially if they have UV or ozone, they might have a hard time meeting permit levels. A typical 3-4 MGD plant can sometimes get as high as 10-15 MGD flow with very heavy rains! That is incredibly hard on a biological plant to handle.

Droughts or fires on the other hand can cause problems to the opposite extreme. Dry weather for municipalities can tend to cause the flows to go lower, the MLSS to get significantly older and filaments sometimes can dominate due to longer MCRT and lower F/M ratios. When this happens, adjust your bed levels in your clarifier, lower your MLSS according to your microscopic evaluation. If you typically run at a medium age sludge and stalked ciliates and a few rotifers are dominant, but suddenly you only have rotifers and many worms, you know you are too old and need to increase wasting.

Fires can cause additional problems, especially if inside the plant such as an industrial site, or a fire in a city and the water
from a house burning is flushed down the drains. The chemicals in the water may be harsh, impact the pH and alkalinity in the system, they may have significantly higher BOD levels and need an adjustment to the MLSS. There may be foaming chemicals that were used and this may cause foaming on the aeration basins. There may be toxic chemicals to the biomass or specifically the nitrifiers.

Watch your system carefully after a fire, run more tests, check your nutrients if the incoming stream is higher in BOD. Look under the microscope at the bacteria, they will tell you what is going on long before it becomes critical.

Cold weather extremes can significantly impact a wastewater treatment plant. Did you know that for every 10° in temperature that the MLSS drops, the activity of the biomass changes one logs growth!!! Obviously, that means if the temperature drops below 70° or 60 F, you will have to increase your MLSS. If it gets really cold, you may need to carry a MLSS and have a higher bed in your clarifier 2-3 times what you do in the summer months