Most, if not all, biological wastewater treatment plants are either not working or are not functioning efficiently to their expectations. This sad state of affairs gets worst with time due to changes in the operating parameters of the WWTP or due to poor monitoring and servicing of the WWTP.
The main contributing factor to this poor state of WWTP probably arises out of the attitude of the companies regarding the WWTP as a liability in that it does not contribute to the profits of the company. It is not surprising therefore that they will not invest more money in operating and maintaining the WWTP efficiently. In the first place they build the WWTP more as an excuse to get the necessary operating license to carry out their manufacturing activities
The WWTP has always been situated at the back of their manufacturing premise and not in front of their minds. The full realization and impact of poor housekeeping in maintaining an operating WWTP only comes too late when Department Environment officers slap them with compounds and threatening imprisonments and forced transfer of their manufacturing facilities
FAILURE OF WWTP
The failure of WWTP could be attributed to many factors such as design oversights, poor operation, poor maintenance and servicing of the WWTP. These various failures will ultimately affect the performance of the microbes in the WWTP which will ultimately affect the performance of the WWTP. After all a biological WWTP is nothing more than a bioreactor that support the growth and function of high concentration of microorganisms
NATURE AND CLUE FROM FAILURES
WWTP failures reflect both the state of the pathology of the WWTP and give us vital clues to the where and why the WWTP fails. We should try to study the nature of these failures scientifically so that it will aid us in our decision whether we can repair, replace or improved the WWTP process. Failing to do this we might end up in the future building or renovating the WWTP which will end up in similar predicament years later
MAIN TYPES OF FAILURES
There are generally failure two main types of failures:
1 Sudden failure
2 Gradual failure
Sudden failure of WWTP is a failure that is not anticipated and usually occurs immediately beyond our control. Examples of sudden failure are electrical outage, blower burnt out, toxic chemicals or sudden hydraulic loading due to heavy rain. The impact of sudden failure is often very serious which can throw out the WWTP out of its function
Gradual failure of a WWTP occurs slowly and show cumulative deterioration with time. It is usually reflective of slow breakdown of system. Example of gradual failure of WWTP is exemplified by gradual clogging of the porous filters used in supplying air to the WWTP. Such failures could have been averted as the signals of impending failure are there. Such failures could have been avoided if remedial actions such as repair taken before turning to disaster
Previous records if kept could have indicated clues of impending failure, when the performance of the WWTP is slowly spreading out of optimum band state of operations. We should be able to see the loss in treatment efficiency of the WWTP over time in terms of BOD, COD and TSS reduction
WHY MOST WWTP FAILURES GO UNDETECTED?
In reality most failures go undetected because there are no staffs that are trained to monitor the performance of the WWTP. By the time the WWTP completely broke down, it is already too late to take preventive actions
Even if monitoring of the WWTP is carried out, it usually involves ‘end of pipe’ analyses and not ‘up pipe’ or ‘along pipe’ analyses. In most cases the analyses just involved the basic regulatory requirement parameters such as BOD, COD and TSS. These parameters are insufficient to show the state of health of the WWTP and you do not really know which unit process is facing the problem?
IMPORTANCE OF ADDITIONAL PARAMETERS MONITORING
There are other parameters besides BOD, COD and TSS to give us the clues on the exact state of health of the WWTP. Any changes in the operating parameters of the WWTP will be reflected by the gradual change in the composition and properties of the microorganisms of the WWTP. There will also be changes in the chemical; parameters in the mixed liquour due to the changes in the microbial consortium in the WWTP.
The failure for nitrification could be indicated by very poor DO and high NH3 content of the wastewaters. High biomass washouts could be attributed presence of pin flocs within the WWTP are some of the examples of how additional parameters monitoring help to determine WWTP failures
To confirm the observations there might be the need to carry out scale down studies to pin point the cause of the WWTP failure. Samples of the mixed liquour from the WWTP are removed and transferred to various smaller vessels to study the effect of mixing, aeration or oxygen uptake. From the studies we can conclude if enough mixing or aeration are the culprit of the WWTP failure.
Wastewater treatment in a WWTP usually involves the flow of the wastewater through a series of unit processes which include physical and biological treatment
2 Which unit processes are the rate limiting steps and controlling the bottleneck of the process?
3 Which unit process are the ones having problems?
Simple measurements can be conducted by using ph and DO probe with long cables, together with simple tracer studies to see the problems of flow and circulations within the WWTP. Any short circuiting or improper mixings of the WWTP will be easily noticed
The success in determining the cause of plant failure and inefficiency will allow rapid action to remedy the situation or even to optimize the rate limiting steps in the wastewater treatment process. This will allow the factory to save time and costs.
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