Implementer's Guide to Lime Stabilization for Septage Management in the Philippines

  • JKMakowka
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Re: Implementer's Guide to Lime Stabilization for Septage Management in the Philippines

To my (theoretical) understanding it is the high pH (12-13) that kills the bacterial. Thus after de-watering the sludge in unplanted drying beds, the percolate can be pH adjusted to neutral levels (6-7) by dosing an acid to it.

I guess industrial grade sulphuric acid might be the cheapest and most easy to get option, but citric, lactic or hydrochloric acid will probably work as well with less environmental impact. Lactic and citric acid might even be beneficial to the subsequent biological treatment process as both should also work as a carbon food source for many bacteria.

Worth a try for sure :)

P.S.: Please ensure that your stock of lime and acid is well separated and that your workers are acutely aware of the danger of mixing highly concentrated acids with quicklime directly!

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  • pkjha
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Re: Implementer's Guide to Lime Stabilization for Septage Management in the Philippines

It does not appear economically sustainable to add acid to lower pH from 12-13 to 7 for Kilo liters of waste water on daily basis. .


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Re: Implementer's Guide to Lime Stabilization for Septage Management in the Philippines

pkjha wrote: It does not appear economically sustainable to add acid to lower pH from 12-13 to 7 for Kilo liters of waste water on daily basis. .


Yes, that is the conventional wisdom for waste-water treatment plants. It might apply to this specific situation or it might not...

I would guess if it is economically feasible to raise the pH to that level for all the wet sludge, lowering it again for just the percolate is probably feasible as well.

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  • kharallaxman
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Re: Implementer's Guide to Lime Stabilization for Septage Management in the Philippines

Thanks for the response. The problem sought to be addressed here is not pH neutralization however - the pH after lime application is reported to come to neutral naturally. The question is how to make sure that biological treatment processes following lime application would not be compromised due to the dying of pathogens and halting of microbial degradation due to the lime application.

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Re: Implementer's Guide to Lime Stabilization for Septage Management in the Philippines

kharallaxman wrote: Thanks for the response. The problem sought to be addressed here is not pH neutralization however - the pH after lime application is reported to come to neutral naturally. The question is how to make sure that biological treatment processes following lime application would not be compromised due to the dying of pathogens and halting of microbial degradation due to the lime application.


Not sure I can follow...

While the pH will probably decline a bit due to the drying bed process removing some precipitated lime and natural CO2 capture from the atmosphere, this will take quite some time and I doubt it will reach neutral levels easily. But again, theoretically speaking, as while I have visited such a lime treatment plant in the Philippines, I was not involved in the day to day operation and process optimization.

Thus the problem to my understanding is the high pH that will have a strong impact on any subsequent biological treatment process or natural streams if directly discharged (in the system I visited it was discharged into a solid-waste dump side and thus there was little to make worse). After all the two main purposes of adding quicklime are to stabilize/precipitate solids in the sludge and the same time rise the pH to levels that kills most of the pathogens.

However besides having to neutralize the pH, it might also be necessary to inoculate any biological treatment process with bacteria from a well running system as the percolate from the lime treatment system will have few beneficial bacterial left to colonize the biological treatment system by itself.

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  • pkjha
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Re: Implementer's Guide to Lime Stabilization for Septage Management in the Philippines

Dear Kris and All

Query by kharallaxman is still unanswered. The issue has been discussed previously on the forum. Use of lime stabilisation at some sites in Philippines has been highlighted previously. You also mentioned it. However, it does not mention treatment technology of filtrate. Disposed of effluent on solid waste dumping ground is not a solution. pH may come to neutral as mentioned by kharallaxman. But what is time requirement?
Application of lime has been reported for some sites in Cambodia. If someone has report on treatment of effluent in that country, pl. share.
During previous discussion I had raised some fundamental query. Lime does not cause stabilisation. Lime stabilisation is a misnomer. Killing of bacteria / pathogens is not stabilisation. Purpose of septage management is the safe reuse of solid as well as liquid parts. Lime may have beneficial for one part but causes serious problem for another part.

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  • dmrobbins10
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Re: Implementer's Guide to Lime Stabilization for Septage Management in the Philippines

From USEPA: "Stabilization of biosolids helps to minimize the potential for odor generation, destroys pathogens (disease causing organisms), and reduces the material’s vector attraction potential. One method of stabilization is to add alkaline materials to raise the pH level to make conditions unfavorable for the growth of organisms (such as pathogens). Where lime or another alkaline additive (for example, recycled kiln dust), is relatively inexpensive, alkaline stabilization is often the most cost-effective process for wastewater solids stabilization. This is particularly true where dependable markets for the alkaline product can be developed, such as in areas where alkaline materials are routinely applied to agricultural soils to maximize crop yields. "( www.epa.gov/biosolids/alkaline-stabilization-biosolids )

From my perspective, for municipal FSM systems using the technology, best to first concentrate the biosolids using sedimentation or some other process prior to dosing with lime. That will minimize the amount of high pH liquids, which could then be reintroduced into the liquids stream for treatment. One could also mix the effluent with water from hand wash facilities at the site, and even septic tank effluent from the facility restrooms to dilute the lime treated effluent while reinoculating the effluent with microbes. My guess is that traditional effluent treatment systems would function well in this type of scenario, although to my knowledge, that has not yet been tested. It would be very interesting to do some research on the effectiveness of ABRs or wetlands for dealing with lime impacted effluent to be sure.

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Re: Implementer's Guide to Lime Stabilization for Septage Management in the Philippines

Dear Robbins and friends,
Could you please suggest how the said research on the effectiveness of ABRs (including Anaerobic Filter) and wetlands for dealing with lime impacted effluent could possibly be carried out in a simple way. And are there any potable equipment you know that could possibly be used for testing necessary parameter onsite? Thank you again for responding and for helping in taking this discussion ahead.

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Re: Implementer's Guide to Lime Stabilization for Septage Management in the Philippines

I think that conducting the described research would require a pilot scale system that that would treat small quantities of lime impacted effluent at different concentrations to represent different levels of dilution. Ideally the research would take place at an existing fecal sludge treatment plant where there is a steady stream of septage. Testing the ABR should be relatively straight forward using BOD as the indicator of treatment efficiency. A pilot scale multi-celled constructed wetlands could be constructed to test different plant communities that might be better adapted to high pH. A literature review would be useful as there has been some research in utilizing constructed wetlands for treating high pH commercial effluents. Some of these findings might apply to high pH septage effluents. As for portable testing systems, the Hach Company has a broad range of equipment that might be used. Here is a link to their portable BOD testing equipment: ( www.hach.com/bodguide ).

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  • kharallaxman
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Re: Implementer's Guide to Lime Stabilization for Septage Management in the Philippines

Thank you so much. And what about disposal of lime treated effluent through infiltration underground – what could possibly be the risks and precautions or preparation necessary and where such disposal may be possibly.

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Re: Implementer's Guide to Lime Stabilization for Septage Management in the Philippines

As far as soils application of lime impacted septage effluent, my sense is that as long as the soils dispersal system is designed for the Long Term Acceptance Rate (LTAR), the system should work properly. This would include making sure to consider in the soils dispersal system design the soils texture and structure, consistence, depth to groundwater or other limiting feature, and the landscape slope and position. Here is some guidance: ehs.ncpublichealth.com/oet/docs/cit/oswp...hapter4-Section6.pdf

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  • sahidul93
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Re: Implementer's Guide to Lime Stabilization for Septage Management in the Philippines

Laxman's last paragraph: This is in connection with an emergency FS treatment plant where the faecal sludge is quite fresh (about three months old) and there is lack of space to store the FS for a longer time before application in the unplanted drying bed. With lime application it is supposed that the FS will become dewater-able quickly in the unplanted drying bed.

I am working with UNHCR at Cox's Bazar, Bangladesh where the largest influx happened recently. Some of our partners have already started lime stabilization as this is a real challenge to manage the excreta rather than septage. As this is more of fresh sludge, the technology might be a good option. Biogas also may be a good option.

I have some experiences on FSM, working in urban areas of Bangladesh. But in Rohingya camps, the scenerio is totally different. Collection is the real challenge as they are staying at the top, middle and valley of the hill, transportation is very difficult.

@Dave Robbins: you mentioned about working in Myanmar. What is the results now?

What are the sequences of lime stabilization: Dewatering, Solid-Liquid separation, Drying bed, Leachate treatment (Constructed Wetland),

Any better idea?


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