Water & Decentralized Wastewater Knowledge Exchange Forum

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Decentralized wastewater treatment


Decentralized wastewater treatment seems to be gradually gaining a foothold in my state of Ohio as a solution in situations where neither the “Big pipe” or individual onsite systems can be used exclusively to fix water pollution problems caused by failing or sub-standard septic systems.  Although the decentralized concept is being used in a few places, the whole idea is still relatively new here.  If anyone on the forum has any personal experiences working with decentralized systems, please share them here so we can all learn from them.


2 thoughts on “Decentralized wastewater treatment

  1. One of the biggest concerns in these types of systems is septicity from transported waste Ideally, from an engineering standpoint, having complete mix or step feed configuration is desirable to spread out the organic acids (formed during anaerobic reactions during transit). Hydrogen sulfide can be toxic to many of the floc forming bacteria when the pH is 7 or lower and can also cause growth of filaments such as type 0914, 021N, and Thiothrix. Reducing any H2S prior to treatment (pre-aeration etc) may be beneficial- possibly in a small aerated equalization tank if flow varies considerably.

    Also, a common concern is variability of different types of waste. “You are what you eat”. If the bacteria are used to a certain substrate and a different type of waste comes in, this can cause a shock to the system in which the new bacteria proliferate causing dispersed growth etc (changing of the guard). As noted, surfactants, toxicants, and other nasties have potential of getting into the system.

    I personally believe that they can work, but require a high degree of vigilance on testing and monitoring what comes into the plant.

    best regards,

    Ryan Hennessy


  2. Hello there,

    Thanks for participating in the forum. We really appreciate your efforts in bringing new ideas to forum. Decentralised wastewater treatment systems are becoming common practice in my country India. Now days for almost every other residential or commercial establishment within areas where piped connections are not available, it has become mandatory to install a decentralized WWT for the community.

    Key issues I have seen with DEWATS are efficient design to cope up the load fluctuations which seems to be very important to me. For large plants, due to a wide catchment area a lot of kind of qualitative and quantitative equalization to wastewater flow and composition is available.This might be missing in a small DEWATS for a small community. Thus, the design should be localized rather than packaged which is a common practice for DEWATS.

    Another issue I see health and safety concerns as if the treatment given is not complete (which is the case in India for all DEWATS), it could damage the local environment rather than helping it. If you are using the treated effluent from DEWATS for some reuse and recycle application like Gardening, irrigation then you need to consider the treatment given and local environmental conditions very well. Though a lot of guidelines available for it.

    For almost all DEWATS , sludge management is an issue. Dont know how people address it. Most of the time un sustainable practices are implemented.


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