Wastewater Treatment Plant Optimisation PLANT B - Case Study

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Site Details: PLANT B, Co. Cavan, Ireland.

Operator details: Undisclosed

Description of Wastewater Treatment Facility: PLANT B is a Municipal wastewater treatment plant which has primary clarification followed by a splitter chamber where the flow is split between 2 trickling filters with plastic media and an RBC. These operate in parallel. The treated wastewater flows through secondary clarifiers before it is combined and flows through a horizontal flow reed bed before discharge to the river.

Difficulties encountered on the WWTP

The flow to the RBC was quite consistent but the flow to the two trickling filters was variable with the result that distribution on the trickling filters was poor. The medium is structured plastic so it is very important that it is kept moist to prevent drying out of the biofilm. While results from the RBC were quite good the results from the trickling filters were inconsistent. This was resulting in variable final effluent BOD and- in particular, ammonia.

Solution from: Combined Environmental Technologies

Combined Environmental Technologies was approached for help to boost the biomass growth through the supply of carbonaceous bacteria as well as nitrifiers to restore the biomass growth to support the ammonia removal.  

Combined Environmental Technologies engineers are specialists in plant optimization and providing affordable technological solutions to wastewater treatment operators who have ongoing issues with their plants, whether the plant be overloaded, over capacity or simply not regularly meeting discharge standards.

Detail of Operations to remedy the problem

1.       The first action was to better balance the flow to the two trickling filters to make sure of consistent loading on the beds.

2.       Dosing of carbonaceous bacteria was conducted with initial dosing on a daily basis. The objective was to build up a strong and efficient biofilm on the medium.

3.       The boosting of the biofilm was also designed to improve BOD removal and to reduce any inhibition to nitrifiers before these were added.

4.       Dosing was also conducted on the RBC since that is also an attached growth system.

5.       Once the biofilm had been established the second objective was to dose nitrifiers to the medium as these can then stick to the existing biofilm.

6.       Once the system has been inoculated all that is required is to have regular weekly maintenance dosing to help maintain the biofilm population of efficient carbonaceous bacteria and maintain the nitrifier population in the plant.

List of products used to remedy the problem:

a)       BFL 4000SU - This is a natural microbial product which has been specially formulated to deal with municipal wastewater. It contains a wide range of strains which have the ability to degrade the organic materials found in municipal wastewater. It also has the ability to form biofilm on plastic media in a quick and efficient way.

b)      BFL 5800NT - This product contains a blend of nitrifying organisms which can quickly establish and attach themselves to an existing biofilm. In this way a strong nitrifier population can be quickly established so that ammonia oxidation can be restored.

Long Term solution to keep the AS strong

A weekly dosing program was established for the facility and is now administered by Combined Environmental Technologies at regular weekly intervals to maintain the biomass population of efficient carbonaceous bacteria and maintain the Nitrifier population in system to help strengthen the systems performance and to help the facility to recover quicker from occasional overloading. It has been observed that following initial dosing and regular biological maintenance that the plant biomass is more robust and recovers faster from upsets. Good biological growth is now evident on the Trickling Filters due to the program and is delivering more consistent results.

Weekly Lab Testing is essential to monitor the results from the plant to ensure performance is maintained. If performance starts to decline action can be taken to correct things before they get out of control.

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