Effect of a Stormwater System in WWTWs?

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What is the effect of a Stormwater Management System within Wastewater Treatment Works (WWTWs)?

How does it affect Wastewater Treatment Works during extremely heavy precipitation? What should be done in such cases to mitigate the heavy stormwater inflow?

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10 Answers

  1. The effects of high hydraulic loading in a treatment plant due to stormwater inflow and infiltration, and what you can do to manage the excess flows, depends on the type of treatment process you are operating and the unit components.  As others have noted, suspended growth processes like conventional activated sludge can be adversely effected as the high flows reduce the hydraulic retention time in the bioreactor (reducing the level of treatment, flush suspended biomass out of the bioreactor, and overload the clarifier resulting in excessive biomass loss.  MBR processes, while they don't lose biomass, are probably the most sensitive to hydraulic overloading due to the limited flux rate that can pass through the membranes.  Fixed film and hybrid processes are much less susceptible to biomass loss, as the bacteria are attached to surfaces and are not easily flushed from the system.  If you have an activated sludge process, and are having biomass retention problems, you could consider an MBBR conversion.  Equalization storage is a good initial approach, and can usually be retrofitted or expanded for any plant design.  Regulators in North America will often allow excess flows beyond 2 times the average dry weather flow to bypass the secondary or tertiary treatment process, while requiring the water to at least be passed through a primary clarifier and may require chemical enhancement.  Generally blending enhanced primary treated bypass flows with fully treated secondary or tertiary flows for short periods will minimize the effluent degradation.  There are also a few clarifiers that can better tolerate extended periods of high hydraulic  loading, such as the Veolia Actiflow  which incorporates a carrier, chemicals and plate separators to enhance solid separation under high flow conditions.

  2. When a heavy influence of stormwater impacts a WWTP, the massive influx of extra water can effectively disrupt all levels of Treatment (Primary, Secondary, Tertiary, and Quaternary). This is especially disruptive to digestion technology (Aerobic and An-aerobic). The preferred methodology for prevention is a stormwater bypass system that absorbs the excess flow and recirculates it through a retention system until the main treatment process can incrementally facilitate treatment. The key critical aspect for success in managing this circumstance is to have comprehensive hydrologic data sets to calculate any given Region's peak flow event horizon volumes; so that your facilities bypass system is large enough to handle the excess stormwater.

  3. Again these type of process is acceptable in area where there is enough capacity of dams (i.e. emergency dam or buffer), is where storm water management system (SWMS) is important and we can't experience any pollution in the stream or catchment. Bear in mind that other countries are scares water country and the conservation of water is very important.  

  4. The effects is only overloaded of the treatment works, and flushing of nutrients into the stream. removing some of the important bacteria at the treatment works. After WWTWs receiving too much inflow, the treatment works will smell as sign of starting treatment works afresh.  

  5. What is your system designed to do? Is it CSO or meant to have separate stormwater and sewer streams? The answer to this is important in answering your question. If combined, then the advice you have been given is relevant, If not, then you need to determine if the stormwater influx into your sewer system is mainly from inflow or infiltration, or both. It is at this point that the rectification becomes interesting.

  6. A combined sewer is a sewage collection system of pipes and tunnels designed to also collect surface runoff. Combined sewers can cause serious water pollution problems during combined sewer overflow (CSO) events when wet weather flows exceed the sewage treatment plant capacity. This type of sewer design is no longer used in building new communities ( current design separates sanitary sewers from runoff ), but many older cities continue to operate combined sewers. 

    You can find the Combined Sewer Overflow Documents here :

  7. French English

    Bonjour

    L'eau de pluie a un rôle à jouer dans l'environnement au niveau des sols. ajoutée aux eaux usées cela ne fait que poleur notre environnement encore plus car si l'eau de pluie dilue la pollution des eaux usées elle ne la supprime pas.

     A cela il faut ajouter que toutes les stations d'épuration sont équipées d'un by-pass qui permet lors de fortes précipitations pluviales dont une partie a envahi le réseau d'eaux usées, de délester la STEP, en envoyant directement dans le milieu hydraulique le surplus d'eaux usées, mélangé à la pluie.

    L'apport d'eau pluviale n'affecte aucunement le traitement des eaux usées, elle augmente le débit. Le processus de gestion des eaux usées sur la STEP doit être modifié pour évacuer la surabondance.

    Le traitement séparatif des eaux usées consiste à débarrasser les matières solides flottantes du volume liquide. Il n'y a aucun traitement d'épuration et toute la pollution dissoute dans le liquide est dispersée dans l'environnement

    La réglementation interdit toute adjonction d'eau de pluie dans le réseau d'eaux usées.

     

    Hello

    Rain water has a role to play in the environment at the level of the soil. added water waste it does than poleur our environment even more as if rain water dilutes the pollution of waste water it does not delete it.

    It must be added that all treatment plants are equipped with a by-pass that allows during high rain precipitation which part has invaded the network of sewage, relieve the STEP, by directly sending in the hydraulic medium the surplus of waste water, mixed with the rain.

    Rain water does not affect the treatment of wastewater, it increases the throughput. Wastewater on the STEP management process should be changed to remove the glut.

    The separate treatment of wastewater is to rid floating solids from the liquid volume. There is no sewage treatment and all the pollution that are dissolved in the liquid is dispersed in the environment

    The prohibits any addition of rainwater in the sewage network.

     

     

  8. Hello;storm water in reasonable amounts is meritable to the waste Water Treatment Systems because the water dilute the contents in the waste water stream and reduce the toxicity of some materials for instance TDS.The stream retention period is reduced and moreso the systems are cleansed especially if channels or systems resembling the tunnels are present withing the system.In instance of heavy PPT inflow lagoons might overspill and therefore technical advancement in such systems is demanded. Wetlands be it natural or constructed wetlands have been used to calm the impacts of heavy downpours(used as shock absorbers).Apparently,I am working on a project where we have used such a shoc absorber and a recycle channel to feed back some micro-orgs in a WWTS.

  9. You will need an overflow basin large enough to hold excess flow until storm event is over.

    Then just cycle the excess through the plant when storm is over. You will need to clean the basin when you have emptied it. Plan the basin to handle your largest storm event.