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

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

Lime stabilization is a relatively low cost and effective method of treating septage. It has been used for many years in the United States but is now just catching on for municipal programs in the Philippines. In 2008, The United States Agency for International Development (USAID) introduced the technology in pilot programs, but it wasn’t until typhoon Yolanda (international name Haiyan) struck the central Philippines two years ago when the technology was used at scale. Disaster relief workers from Oxfam and other NGOs discovered that lime stabilization facilities were easy to set up, and required low capital outlays and a small land footprint. Cities, such as Tacloban City in the province of Leyte, eager to set up low cost and sustainable septage management programs are now starting to realize these benefits through the implementation of full scale systems.

USAID has captured these lessons learned and combined them with international best practices in a new manual entitled, Implementer’s Guide to Lime Stabilization for Septage Management in the Philippines. This is an output of USAID’s Be Secure Project. While some of the text is specific to permitting requirements in the Philippines, readers will find the information useful elsewhere. The manual is attached here for your use. I hope you find it useful and would be interested in hearing your comments.


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

Dear David,

This is a interesting and useful publication, written in a simple, easy-to-understand format.

What would be the cost of treatment? Are there any case studies (countries where lime treatment is used)?

Regards,
F H Mughal

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

Thanks for your comment. The costing for a small plant processing about 20 cubic meters per day (roughly 5,000 cubic meters per year) is estimated to be about $10 per cubic meter for the treatment(Philippines prices) considering:

- Cost of the plant (depreciated over 5 years);
- Labor to operate the plant;
- The cost of the lime; and
- Administration.

After year 5 when the plant is paid off, the cost for the treatment per cubic meter drops to about $6.80.

For this costing example, the target community has 10,500 homes and the desludging frequency is every 5 years. The tariff comes out to just under $1 per family per month, all in, including collection and treatment.

The cost estimates are still a bit hypothetical in the Philippines as up until now systems utilizing the lime stabilization technology have been subsidized by donors and the collection and treatment has been erratic. The larger scale system under construction in Tacloban City will provide some better numbers, and lots of lessons learned to be sure, so please stay posted for those.

David M. Robbins
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Re: Implementer's Guide to Lime Stabilization for Septage Management in the Philippines

Thanks for the cost analysis. Any case studies?

F H Mughal

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

There are lots of case studies in the Philippines with real data for septage program business models, full cost recovery and tariff setting, but none yet for full scale lime stabilization programs. At least one program (Tacloban City) will be starting up this year but real data will not be available for some time.

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

Thanks for the feedback. I'll look forward to the Tacloban city data, when it is available.

F H Mughal

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

Dear David, What an excellent manual ! So great to see a practical, balanced report like this.
regards
Graham

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

Dear David and All
I failed to see your earlier post on lime stabilization for septage management. The topic is much relevant for many countries. There are several papers/ guidelines in different countries, highlighting use of lime stabilization for sepatge management. I have a few queries:
i. Application of lime to increase pH to12 will definitely eliminate pathogens, other bacteria and helminths from septage. The Implementer's Guide of USAID also mentions that there is no chance of re-growth of bacteria when treated with Lime. It also mentions that after passing septage through sand filter bed, effluent should be treated through ABR technology.
ii. Now the simple query arises how a biological treatment system like ABR would function for the treatment of effluent having such high pH and without presence of bacteria in the system ( bacteria are already eliminated by using Lime).
iii. The Guide uses terminology— Lime stabilization. I think function of lime is only to eliminate bacterial and other pathogens. It never results in stabilization of organic matters. Stabilization is a completely different term from pathogen free environment.
I’ll be happy to have response from you and other members of the Forum.

Regards
Pawan

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

Dear Pawan,

Thanks for your questions. First it is important to know that lime stabilization will not eliminate all of the pathogens, but certainly most of them. Also, it is more accurate to say that the process limits regrowth of bacteria, and not that there will be no regrowth. We don't want to over-sell the technology.

It is a good question about the ABR function. From our experience, the use of the ABR after the lime stabilization process functions more as a mechanism for additional physical separation for whatever solids remain in the wastewater stream after the sand filtration, where the bulk of the suspended solids are removed. The ABR also provides detention time of between 1 and 3 days which allows the pH to drop to a level more suitable for subsequent treatment, such as the constructed wetlands.

As for the term "stabilization", it has actually been used for years. The US Environmental Protection Agency utilized it back in 1978 in their "Full Scale Demonstration of Lime Stabilization" document that looked at different application rates of hydrated lime for wastewater, return activated sludge, and septage. I would suspect that there actually is some degradation of the biosolids that occurs from the reaction of hydrated lime and sludge.

Thanks again for your comments. Please advise if you are planning any trials. I just returned from Myanmar where Oxfam has demonstrated a full scale system serving more than 50,000 people. We are also trying it on a much smaller scale using the in-pit lime stabilization process first trialed by iDE in Cambodia. Seems to have really good potential there.

Dave

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

Dear David

Thanks for the reply.
I am providing consultancy for septage management for 6 cities in Rajasthan State in India, supported by ADB. I am providing unplanted or planted sand filter beds (depending on site condition) followed by treatment options for effluent. I am not recommending lime due to its recurring expenses and precautionary measures required during handling by semi-skilled workers at the sites. Moreover, in the State, atmospheric temperature goes up to 500 C, sufficient to kill pathogens on drying beds. If frequency of loading is decreased by increasing number of beds and maintaining the sludge height of 20 cm, dried solid mass of desired level can be obtained with least chance of survival of pathogens.
Effluent from filter beds has high BOD – around 500 mg/l. It’s challenging to treat it to the acceptable level of discharge or reuse. Lagoon is not suitable to meet the discharge norms. Moreover, it requires large space- not normally available in urban areas. Anaerobic system is also not suitable to meet the discharge norms. I will use aerobic system with bacterial growth media. Lime is also not suitable as in such case population density of bacteria in effluent will definitely reduce, resulting in lower efficiency of the treatment system.
One simple suggestion-- Is it possible to use lime with higher doze in the septage only during the last loading of the filter bed? In such case lime will kill pathogens in solids on filter bed. Earlier effluent will have normal population density of bacteria. Effluent of last day will have little volume, of course with higher level of lime concentration. But total concentration will be much lower with little or no change in pH.
Regards
Pawan

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

Hi Pawan,

It is a great suggestion and I think it would be easy to test. Recommend setting up a simple jar testing bench scale treatability study. Easy and inexpensive, and will provide you with information on the required dosing of hydrated lime for this application. If you try it, please let me know what you find out.

thanks for the post,

Dave

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

Dear dmrobbins and colleagues,
Greetings !
This is to seek if any evidence has emerged on - how long after lime application regrowth of pathogens may occur again for normal biological process to take place in the units such as Anaerobic Filter and Horizontal Flow Wetland receiving liquid separated in un planted drying sand beds from sludge treated with lime . Or is there any dose or extent of lime application that can without inactivating all the microbial activity just make the sludge dewater-able in the drying bed without affecting the downward biological process in anaerobic filter and horizontal flow wetland significantly? Or alternative, how this could be addressed?
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.
Thanks.
Laxman

Asia WASH Adviser, Terre des hommes
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