Is it possible to estimate mass balance in a Storm water drain during bioremediation?

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Dear Fellows,

I'm working on In-situ Bioremediation in a storm water drain which is receiving domestic sewage from nearby areas where proper sanitation facilities are not available. This drain is not a channelized structure means width and depth are not same along the complete length of 14 Km. It's receiving sewage through 5 lateral lines also. Total flow in the drain is 120 MLD (Million Litre per day).

I'm using Bioremediation process with strict and facultative anaerobic bacteria to treat the pollution and bring down BOD and COD up to 20 mg/L and 50 mg/L as per standards of Indian authorities. My question is:

Can we calculate Mass balance in such drain where dimensions can't be calculated properly?

Secondly the concentrations of major pollutants are also changing tremendously with the flow?

If anyone having experience working such project please advice me for the same.

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13 Answers

  1. It depends if you have dry or wet weather flow. If it is dry weather flow, you can use approach from numbers of connected inhabitant (per-capita approach as mentioned previously by Rakesh Mehrotra. You can then estimate the average slope and cross section to approximate the dry weather flow. The concentration of contaminant in dry weather flow does not depend on the flow (since there is no dilution from external sources such as rain water) but depends on possible chemical reaction which takes place along the drainage channel especially if it is an open channel. You have to measure it in the WWTP inlet.

    If it is wet weather flow, it will be more difficult since you have hydrological parameter inputs. You need to have the rainfall input and rainfall-runoff model. One model I know is EPA-SWMM which is built particularly for stormwater modeling. The concentration of contaminant also depends on dilution rate (amount of storm water flow) if you have wet weather flow.

  2. Yes it is, in India our associate companies has developed such products and are being used in domestic sewage 

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  3. For scientific design, the position of laterals entering the drain through its length of 14 KM will be of relevance

  4. We have Phyco and Bio Remediation a 16 km drain, 200 MLD and perhaps going to do a much larger one. We work on mass balance but its not that precise.  You could call me anytime day after tomorrow on 9958066588/Gurgaon. 

  5. It is possible by taking per capita approach if population of area connected to sewage drain is known. Alternatively , from the BOD  mg/l, the BOD loading kg/d to the treatment plant can be estimated by  effluent discharge( Q effluent). Discharge measurement from treatment plant  is easy.

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    1. Thanks Rakesh for your comments. Actually it's not a treatment plant. it is an open stormwater drain which is receiving domestic sewage from different residential areas adjacent to the main drain. It is not a proper channelized concrete structure. The width and depth are not constant. This is the reason mass balance is difficult to calculate. 

  7. As I think, you can calculate  the ​mass balance at it's finel outfall, 

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  8. I’m thankful to all fellows for responding to my question.

    The project is in India. The drain is passing through residential areas hence receiving only domestic sewage. We have fixed about 11-12 sampling points in complete stretch of 14 km & 5 lateral lines. Our main focus is on estimation of BOD in these samples. Based on BOD we adjust doing of bacterial consortium containing strict & facultative bacteria. We are doing at the point of origin of each lateral and in main drain we have fixed 6 dosing points.
    Normally initial BOD is ranging between 150 to 300 ppm. At the outlet of drain before it falls in the river we successfully achieve BOD 20-30 ppm. The process is completely electricity free. 
    We are receiving marvelous results in terms of reduction of organic matter, control of emission of H2S etc but authorities are more interested to know about mass balance.
    According to my experience calculating mass balance accurately in this type of water body is not possible because of following reasons:

    1. The width and depth are not constant somewhere width is 50 m but after 500m it remains 5-6 m only because it’s not a channelized structure with proper boundaries. So it can’t be considered as bioreactor.

    2. Based on our analysis the anaerobic strains are found growing in the sediments thus controlling tge emission and generation of odors completely. So there is no proper distribution of bacterial colonies in the complete volume of water.

    3. initially we noticed the high loss of bacterial colonies but after 15 days they stabilize in the system and we started receiving substantial reduction in pollutants as mentioned above

    I would like to know whether I’m right in my concepts or it’s possible to calculate the mass balance

    Appreciate your comments on above mentioned details.

  9. Manta:  I am not sure which country your project is in as that may make a difference in influent concentrations. In a sewer collection system with 5 laterals 14 Km in length you would first need to calculate the HRT for your anaerobic in-situ treatment contact time and determine if that is sufficient for the anaerobic bacteria to function to degrade the organic materials--as anaerobic processes take longer than aerobic ones to degrade organics, albeit they can function with lower energy costs. If you use standard BOD and COD data for the influent municipal household flow that would be 200 BOD and 250 COD x the 120 mL/day for total organics you can estimate CFUs needed to handle these loads. Treatment in the collection system prior to arriving at a body of water or a treatment plant is a very desirable objective but somehow you would need to keep seeding bacteria since this is a "Flush Through" system and the anaerobic bacteria would need to be continuously replenished in an incubator as they wash away down the 14 Km in length. What provisions do you have for inline incubators dispersing beneficial bacteria? We have made incubators out of simple 50 gallon poly drums that have an imersion-type heater and a peristaltic pump that innoculates the wastewater and continuously dispenses live bacteria into the sewer system where is blends with the flow. Ours was in SE Asia and we had to have high strains of Nitrogen degraders as we had low flow (some non-flush sources--e.g. urinals) and as a result high NH3 concentrations from urine. Challenging project but very doable.  Another simple test would be to add a food grade dye at the beginning of the collection system and determine how long it takes to flow to the treatment works 14 Km away.

  10. Hi Mamta

    You appear to have a natural watercourse which is receiving inflows of domestic sewage (not industrial or trade waste) from five separate areas. The first task is to draw up a diagram of the relevant collection area with the main channel and the laterals which are contributing. You should then look at each of the laterals and calculate the amount of sewage which each contributes based on the connection rate and the population. This can be tested by measurements of the BOD and SS from each branch and in the main channel. This should give you a clear understanding of what is going on and then you can look into the options for remediation. A first test of options would be to do a comparison of the capital and operating costs of treating the main outfall, against putting treatment on each of the individual branches - or even a new, separate collection system. You should be looking for some form of natural treatment such a lagoons or constructed wetlands in the first instance. If you have to go to primary and secondary treatment then costs will spiral.

  11. You cqan probably estimate volume with some cross-sections along its length, and averaging the depth along each section. however, the estimate must consider the inflow from the lateral lines. If you can estimate the volume and retention time, you can try to analyze it as a biological reactor. Another possible way would be to analyze it assuming it is a stream composed of segments, using the Streeter-Phelps equation.

  12. Mamta,

    If you have access to water meter data for the Area of Interest, you can calculate the domestic sewer coming out of them based on the MLD that they use, which will just be a portion of the 120 MLD since the other part would be storm water. 

    Another possible way  would be to evaluate average daily precipitation, substract calculated (or estimated) percolation and evaporation and you would have an estimate of your storm water, the other portion of the 120 MLD would be your domestic sewer.

    I hope that helps.

    Miguel

  13. What about a wier in the outfall of discharge? Or a flow meter? For a weekly span, to judge the amount of flow?