How can solar powered sewage treatment plants help municipalities of a developing country ? Does anybody have some case studies or presentation of the said system?

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I saw a  video on this subject, I did not find enough details of the solar power plant and the methodology adopted. This is also crucial since the region where such STPs are proposed, regionally they should be amenable for solar power and its utilisation. Does any one has experience of working on solar powered sewage treatment plant? Can you share your experience and some technical details of the system? Do you think this system will be helpful for developing countries like India?

Thanks. 

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9 Answers

  1. Amir Dakkak

    Dear Achar,

    Usually in Wastewater treatment plants and sewage treatment plants, the renewable energy used is the one harvested during the treatment process. Methane is produced and it's harvested and then burned in order to produce energy. This energy in turn is used to power the plant itself. For example, this is being implemented in Al-Samra wastewater treatment plant in Jordan, where 40% of the energy required to power the plant is produced through the methane harvested from the treatment process.

    Solar energy is recently being used mainly on desalination plants because there is no methane produced to harvest. This is especially true in arid regions such as the Middle East and North Africa. Saudi Arabia has started projects that incorporate solar energy with desalination plants. In order to further understand this process I found these links: https://www.irena.org/DocumentDownloads/Publications/IRENA-ETSAP%20Tech%20Brief%20I12%20Water-Desalination.pdf

    http://www.solarwaterenergy.net/solardesalinationplant.html

    Unfortunately I could not find any details about using soalr energy to power STP but as the other comments have said UV rays have been used in the water treatment process

  2. I have gone through the detailed comments from my colleagues. I would like to enlighten some of the real facts pertaining today; There are two type of Issues at the moment, 1) Selection of the right low Energy Treatment Technology (obviously it must be low cost as well) 2) Selection of the Energy Source 1) Low Energy Treatment Technology Most of the times in Rural Areas, almost in all countries there is ample land available depending of the cost of the land. Thus Shallow Facultative Ponds, Constructed Wetlands, Trickling Filter Wells (Towers) are some of the almost no energy solutions. Even Decentralized Septic Tanks are one of the promising solution. But when we come to City Areas, then the land is not available or if available then of unbearable cost. Interestingly the wastewater generation from the urban areas are also much higher than the rural areas. Here come the Energy Consuming Technologies, you talk about MBBR, SBR, EA, EAAS, CMAS, TF, RBC whatsoever in Aerobic System most of the power consumed in Aeration and Pumping. 2) Energy Source Still Solar Energy proves to be an expensive solution considering the CAPEX and also long run OPEX. One Sq. Meter of PV Cell could produce just only 300 - 600 watts so producing producing 1kW you need a space of 2 Sq. meter. A small plant of capacity 1MGD normally requires 4,000 to 5,000kWhr a Day so one can easily estimate how much space you would require to produce such energy. Space is one aspect. Now come to Solar Power, normally Solar Power Productive Intensity is considered just 6 - 7 hrs a day in Summer in South East Asia, if you go to Europe then forget about this much intensity duration. And if you talk about Winter, the intensity and angle of sun light also not of much use. This is second aspect. Now consider the Energy Storage (Battery Backup). This is one of the most expensive part and count for huge OPEX. Wet Batteries have effective life not more than 1 - 2 years and if we come to Dry Batteries, that could go some more but still are much expensive. For a very small example, I was just trying to have a 400 gallons per day product water Solar Based Tubewell Plus RO for a remote area and the cost with such system came unbearable even sourcing from China. If some scientist can develop a Very Economical Battery Back Up System; then Solar Panel with inveter could come down to US$ 1 - 2/Watt. Lets hope for the best to utilize this Divine Free Energy Source economically.

  3. Hi Achar! trust my email will fund you well. Yes, I have had the opportunity to fund a a few partially PV powered STP in California - a practice which started about a decade ago when the PV cost was around $10/watt. Most of these projects were on net metering basis and partially subsidized though public funding. Now that the cost of PV has come down to ~ $4/watt installed (much lower in developing countries), it is attracting more and more water and wastewater utilities. I am aware of at least two dozen such facilities. A couple of wastewater facilities, in fact, are feeding their surplus generation from PV, anaerobic digesters, small hydro from outfalls, etc. Another way to reduce aeration load is by using solar powered aerators - a very effective way to enhance biological degradation process especially in oxidation / stabilization ponds. I am aware of few applications where surface aerators were replaced with these equipment. Anyway, I hope this will help you. If you need additional information, please feel free to drop me a line sfc95823@yahoo.com. With very best, Shahid

  4. Solar and Renewable Energy Municipal Water & Sewage

    There are many examples of using solar photovoltaics in municipal solar water facilities throughout the world. Actually, some solar UV systems are also used to reduce water contaminants.  For sewage, biogas systems are more commonly used because you have both biosolids and the off-gas is methane which is commonly flared for safety. Solar photovoltaics makes sense to drive pumps, and security systems and senors, but biogas generators could meet most of the energy load - even use of CHP systems converting the waste heat of the pumps to electricity. - Scott

     

     

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  5. Anaerobic digestor followed by aerobic biofilter system

    Hello dear Achar, how you're doing?

    In Brazil we use Anaerobic digestors as the low energy treatment option. But you still have to have a aerobic treatment after de anaerobic. Then we use biological filters to the solids separation and aerobic step. In this basic process, if the terrain presents a slope, the only energi that will be requested is to punp the efluent to recicle in the biofilter. If you find low energy request pumps and a good solar system, it may work perfectly.

    Regards.

  6. Hello dear Achar, how you're doing? In Brazil we use Anaerobic digestors as the low energy treatment option. But you still have to have a aerobic treatment after de anaerobic. Then we use biological filters to the solids separation and aerobic step. In this basic process, if the terrain presents a slope, the only energi that will be requested is to punp the efluent to recicle in the biofilter. If you find low energy request pumps and a good solar system, it may work perfectly. Regards.

  7. Solar powered STPs

    You do not state the geographical position of the developing countries but if we assume there is both an abundance of sunshine and reasonable space available for a STP, I would suggest the implementation of stabilisation ponds.  These consist of a series of shallow ponds, usually a minimum of four about 1.5 m deep into which untreated sewage is discharged.  Retention period is typically 30+ days but depends on local conditions.  Treatment occurs by a combination of settlement and natural UV but can produce good quality effluents that need a minimal disinfection treatment. They also have the advantage that fish can be farmed in the maturation or final ponds.

    The advantages are little or no external power, little maintenance, no reliance on costly spares and a skilled workforce is not required.  In addition they can provide a protein source and with disinfection of the final effluent, a water source for agriculture.  These systems were first developed in the 1960’s and there are many examples in operation today.

  9. Hi, I am not sure about solar STPs but I can tell you about low cost STPs. One example you might have heard of is DEWATS which uses natural filtration processes and plants in the filtration process. Another option is Aerobix which is a stand alone unit that can treat wastewater to drinking water quality standards jusing minimum electricity. DEWATS has been used extensively in India and Aerobix has been used in Jabalpur Madhya Pradesh to treat wastewater from a nallah entering the river. Regards Meesha