River water treatment - Ecoli removal

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We gathered water samples from a certain river and according to the results‚ more than 1 000 000 units of the indicator microbe Escherichia coli were present per 100 ml of water. The health risk is high for people coming into full or partial contact with water having more than 2000 colony forming units per 100 ml. Untreated or partially treated sewage also contains high concentrations of phosphate and nitrate, which contribute to the eutrophication problems. Which method can be recommended when coming to the treatment of this water? 

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7 Answers

  1. visit alivewater.com

  2. Hi Kgabo, treatment options also depend on what you plan to use the water for.  If you aim is to treat the water as a drinking water supply, you will address the E.coli count with normal disinfection (usually chlorine based chemicals) after flocculation, clarification and filtration (which will also remove a percentage of the e.coli).  The eutrophication status may present other problems if it results in excessive algal growth which may require activated carbon to remove microcystins, tastes and odours.  If the water is to be used for irrigation or recreation purposes, it would be wise to install some disinfection system to prevent excessive biofilm growth in the pipelines and irrigation sprayers/droppers and to protect workers/users.  

    Although the long term approach of the writers below of addressing point sources is fully relevant and supported, this may not help you in the short term, or it may be very difficult to achieve (e.g. sewage discharge from a town or city).

  3. Dikeledi, 

    I would further suggest you review the historical records of the water quality at the sampling point, say last 6 months or so.

    Also check upstream for water quality sampling results, particularly where there are wastewater treatment facilities depositing the final treatment effluent onto the same river.

    In essence, I suggest you conduct a Root Cause Analyses on possible causation factors of the hazard observed.

    Do not forget to activate your Incident Management Protocol given the seriousness of the water quality indicator observed.

    Best of luck.

    Twala.

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  4. Kgabo -- I agree with James and Maria in approach to point and non-point pollution sources. Additionally, sometimes a river's floodplain has ox-bows (old river paths) which can be regraded and reintroduced as naturally revegetated wetland pathways. This allows for pathogen treatment and biodiversity support. I do not know where this has been done (at scale); a good start was made in the US Des Plaines River in the 1980s - there's much current internet info on it. (Your E. coli levels are particularly high and indicate a 'point source' -- like a city...) Best wishes!

     

  5. Dear Kgabo,

    I couldn't agree with James Meyer more. The long-term solution of you problem starts by identifying the pollution sources of the river catchment area, and systematically addressing them. Prioritizing is important. In the river catchment area, start by identifying the main entry points of contamination. It's possible that most pollution comes from diffuse sources, but with a "bit of luck" you some important centralized pollution entry points. Focus on those. Technical solutions are available for almost all contamination sources, in all shapes and sizes. But it's very important to know the loads per source, that is quantity and quality per contamination parameter. There is no technical solution that fits it all, but depending on the location, budget and goals, there are always solutions available. The more you know, the easier it will be to find the best solution. Good luck!

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  6. Hi Kgabo,

    Any treatment without addressing the source of the contamination will only supply a small, clean supply of water without addressing the health for those that  normally come into contact with the water.  Using halogen-based disinfectants will result in undesirable disinfection by-products increasing long-term, chronic health risks.  In my opinion, one should identify the source of the contamination, stop, or limit that source, and then use natural processes to rehabilitate the river system.  This moves into the municipal and political ambit which is fraught with inefficiencies, and where the political will to address the problem is crucial.  Water activism is not well-developed in our country, but intelligent, well-directed activism has its place in our communities.

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