Greenhouse Solar Dryers: A Cost-Effective Solution to Ensure Safe Application of Faecal Sludge in Agriculture

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Non-judicious and long-term application of chemical fertilizers not only deteriorate soil quality but also contributes to climate change effects due to the emission of greenhouse gases during the production and application of these fertilizers. On the other hand, there is an urgent need to look for alternative nutrient sources for food production to feed the growing population.

It is widely known that human excreta is rich in nutrients, specifically Nitrogen and Phosphorous. With the recent thrust on faecal sludge treatment and safely managed sanitation, there is an opportunity to use human excreta as a nutrient source. However, there are concerns of health risks due to the presence of pathogens in faeces. The main cause of concern is the soil-transmitted helminth infections as these are highly resistant to treatment and viable for several years.

In this context, this study was conducted in 4 locations (FSTPs – Faecal sludge treatment plants) of India – Angul, Dhenkanal, Karunguzhi and Devanahalli with the main objective to evaluate the efficiency of polycarbonate-based greenhouse solar dryers in reducing the Helminths eggs in the final treated sludges. Greenhouse solar dryers (GHSD) use passive drying to help increase the temperature and decrease humidity to ensure pathogen kill as well as faster drying.

Scenarios studied under the project:

Following were the assumptions made for the study,

  • Increased temperature and decreased relative humidity inside the GHSD chamber will help in reducing the sludge drying time.
  • Longer exposure of sludge to higher temperature (>50°C) will inactivate Helminths eggs.

GHSD is the polycarbonate sheet installed over the drying beds. This has a parabolic shape to resist wind and to induce greenhouse effect inside the drier. This greenhouse effect inside the drying chamber helps removing the moisture laden air and the moisture content from the drying product (Figure 2).

Solar pasteurisation unit (SPU) follows the same working principle and the structure of the GHSD. However, the height of the roof is less compared to the GHSD. The dried sludge from the GHSD is placed in the SPU. Due to reduced height of the chamber and low moisture content of the sludge, SPU can reach to a higher temperature of more than 60 degrees Celsius which will help eliminating the pathogens (Figure 3).

Galvanised (GI) sheet is one of the most used roofing materials over the sludge drying beds. These are galvanized metals made of thin sheets, coated with zinc. The main purpose of these sheets is to protect the drying beds from getting wet during rainy season.

Below mentioned scenarios were studied under the project,

  • Greenhouse solar dryer (GHSD): Angul and Devanahalli FSTP
  • Galvanised (GI) sheet + Solar Pasteurisation Unit (SPU): Dhenkanal FSTP
  • GI sheet and GHSD: Karunguzhi FSTP.
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Replication Potential of the Uhuru Park Pilot Project from Kenyan Perspective

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The city of Nairobi in Kenya has a population of about 5 million people within the city itself, but the population is estimated to be about 10.8 million within the metropolitan area. The city is grappling with the issue of water, as the current production is about 500 000m3/day, against a demand of 800,000m3/day. Heavy infrastructure and capital are required to be able to bridge this Gap. A strategy that would help in reducing this gap would be most welcome. Sewerage coverage is estimated at about 50%, leaving about 50% to depend on on-site sanitation like septic tank and using exhausters and pit latrines in extreme cases. A method that would enable to bring up a decentralized wastewater treatment plant that do not require heavy infrastructure like sewer networks is most welcome.

The city also has great challenges in the collection of wastewater and fecal sludge because of the fast-growing population due to rural-urban migration, which has accelerated the population growth. Rivers in the city are heavily polluted because of the overflow from the current sewer networks and the discharges from areas like focus settlement that are not connected. The open channel that was visible at Uhuru Park was initially meant to convey storm water but is currently used to conveying storm water melt with sewage from the overflow from diverse areas and institutions.

Currency in Nairobi, the most common wastewater treatment systems are stabilization ponds and aerated lagoon coupled with constructed wetlands as well as conventional treatment systems. But the main problem is that this requires huge infrastructure for collection of sewage and transporting it to a central point. So, the need for decentralized systems is key.

The photo on Page 4 (See attachment) is one of the rivers in Nairobi which is flowing next to an informal settlement; this picture presents the heavy pollution in the river and the environment. This has surely helped the Government to come up with the Nairobi River Rehabilitation Commission to try and clean up these rivers so that the water can be available for other uses. The system being discussed actually falls into that category of helping to clean the rivers. The initiative to have this decentralized system in Uhuru Park was initiated at a very high level, when the President of Estonia visited Kenya, and had discussions with her host President of Kenya on areas of bilateral cooperation. One of the results was that Estonia being fairly advanced in terms of technologies, especially in water and wastewater treatment, could assist Kenya in coming up with very innovative ways of treating wastewater, and that is how the Spacedrip device was booted. The Estonia President nominated the Spacedrip team which was accompanying her to do a pilot in Nairobi, and the Kenyan Government nominated the Nairobi Metropolitan services and the Executive Office of the President to work on the pilot. It was deemed appropriate to pilot this system in a very central place, where it can be accessed by other leaders and institutions from around the country. And that’s how the pilot was positioned in Uhuru Park (See Attachment, Photo in Page 7), one of the main recreation parks located within the Central Business District (CBD) in Nairobi. Anybody coming for recreation within the park can see it. The map (See attachment, Page 6) presents in light green the Uhuru Park, which is a very centrally placed within Nairobi CBD with the major governmental institutions located in close proximity including even the Parliament, the President’s Office, the city hall, major hotels and other business premises.

Uhuru Park was chosen for this pilot because before the installation of this system, potable water was used to irrigate the Park, which is a huge area of over 50ha, with the corresponding pressure on potable water. Indeed, the city is already experiencing a deficit of 300 000, and instead of saving on the water, the same water is used for irrigating the park. So, the idea of putting this system in the Uhuru Park was to make sure that the effluent treated from the system would be used to irrigate the park, and by so doing help in reducing the pressure on demand on the drinking water.

Aqua Consult Baltic designed the technology enabling to connect with the irrigation infrastructure of the Uhuru Park, and there has been a partnership on the consultation during the commissioning and six-months operation of the plant handed over to Nairobi Water Sewage Corporation (NSWC). Ruji Africa was the local partner of Spacedrip helping in the preparation, installation and piloting the automated wastewater treatment and reuse system. We have already obtained an update on environmental impact assessment from a Regulator, which is the National Environment Management Authority.

One of the key benefits of this water reuse system is that it requires a very small space, and the container system can be installed inside a building or smaller areas, unlike the other systems which require huge plots of land (land in a city like Nairobi is very scarce to get). This is therefore a solution to areas that do not have land. The efficiency of the system lies in the total pathogenic removal for key area, because the effluent can then be used for other uses like irrigation. In the future, effluents from this system could also be used in flushing of toilets and cleaning as the case maybe, since most of the water is used for cleaning services. For now, because of the stigma associated with the sewage water, it might be too early to start talking about using it for drinking. It already helps to reduce pressure on drinking water, and it is estimated that adopting this water reuse technology in most of the heavy consumers of water (like tourism, hospitality industries, informal settlements, commercial and residential buildings, food processing…) could help cut the demand for water by about 50%, and then the pressure on potable water could really come down.

One key input of this system is electricity because of both the automation and the pumping within the system. However, this can be addressed in future. Currently, the system also incorporates a partner’s solar system that produces part of the electricity, especially for automation and critical operations of the system. But in future, we think the solar energy should be made the main source of energy by incorporating more solar panels and batteries to store the energy.

Financially, this system gives an advantage, especially saving on heavy cost for the construction of the infrastructure required for centralizing the system. This is the main cost that applies for the sewerage system. With a decentralized technology and no need for heavy infrastructure, specific saving in the cost makes this system a big advantage.

The result of this piloting is supposed to inform and advise the policy makers and help them in the development of by-laws that would be required for some institutions. With the water consumption and discharge of given capacity, it should be of interest to install this water treatment and reuse system in the tourism and the hospitality industry, urban, commercial, building institutions, and the food processing industries. Doing so will also help the private sector participation accelerating the coverage in terms of sewerage and help those involved in the management and control of water demands. So, as an addition to constructing new infrastructure to bring in more water, we can manage the quantity we have better by treating our effluent and reusing it. This is already happening in buildings like the local university of Nairobi, which is harvesting all the water within the building that is then reused in flushing of toilets. This idea is not very far-fetched, and its time has come. Policy-makers need to be advised on that so as to come up with necessary bylaws to help manage the water demand distribution in the country.

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Pilot Project for Wastewater Treatment and Reuse at Uhuru Park Nairobi

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Aqua Consult Baltic was established in 1997 in Estonia, and the technology presented herein came into existence in Kenya thanks to a local company. This mother company located in Germany in Hanover, grew up from there. She implements projects around the world and mainly in Baltic States. This is an engineering and consulting company which mostly specializes on wastewater treatment and derivatives, secondary waste handling and municipal waste treatment plant. The company is currently working on a Slovenia and Vienna Project, which is 550 000PE and also in Tallinn, Estonia for 400 000 equivalents. Given that industrial municipal waste is difficult to predict, it is important to know its boundaries and behavior; so, for this type of waste, there is need to do a lot of modeling which includes fractionation of the wastewater and doing the piloting before providing the engineered solution to the customer. The company deals with oil and gas industry, chemical foods, agriculture, industrial plant, and projects linked to water reuse systems. Currently, the Tallinn water treatment of 400,000 equivalents transforms the surface water into potable water, using new technologies that are developed. The company has built good relations with universities, where testing and research are carried out.

Besides, Spacedrip – also an Estonian company – is an innovative and young company that focuses on water treatment systems which reuse water in a small scale of 25 to top 2000 people for water companies, real estate developers and defense sector. The defense sector for example has mobile units in different places that need to be supplied with water. Spacedrip thus provides them with showering or toilet systems that reuse water continuously.

Relationship between Aqua Consult Baltic and Spacedrip Group

A few years ago, Aqua Consult informed Spacedrip of the design of a new model of houses prefabricated in the factory and deployed to the sites. However, there is occasionally no infrastructure on the site, neither a wastewater nor a drinking water system. They needed a machine which was able to transform wastewater into drinking water. Spacedrip made the design, which is now used in Aqua Consult Baltic factory and the latter developed it further to what it has become today. It is now a more reliable product that can be fully put on automation, a very nice product. This device was funded by the Government of Estonia as a technology to be exported in other countries, and whose added value is the environment-friendly feature and saving the greenhouse potential.

During the funding, the Estonia President at that time visited Kenya. He knew about the existence of this company making wastewater into drinking water; indeed, there is less than 1 million people or so in Estonia, and everybody know each other. He told his peer, the President of Kenya of this technology, and the latter showed interested, hence the relationship with partners on site and the launch of this Kenya project.

Problem Statement

As President William Ruto put it: “Kenya Government has resolved to not only reclaim Nairobi’s reputation as Africa’s green city but also live up to its ancestral identity as the river of cool and fresh water”. The Kenya project emerged from findings below:

  • The river that flows in Nairobi is polluted enough and needs to be cleaned to get the same quality as before the settlements. So, there are a lot of projects ongoing to make this river cleaner and for a better environment.
  • Secondly, Nairobi City water production is around 500 000 m3/day, but the amount needed to meet existing demand is 800 000m3; there is a lack of green water to use.
  • Furthermore, there is lot of drinking water used for some needs that technically safe recycled water could have met (flushing toilets, irrigation, etc.) Indeed, water reuse systems can reduce the water demand by 50% (800 000m3/day is necessary. If 50% of water are saved, then only 400 000m3 will be needed). To implement this project, infrastructure upgrade is not necessary.

A pilot plant was thus installed at Uhuru Park, Nairobi for two purposes:

  1. clean up the Nairobi river a little bit, and
  2. help reuse water.

The Solution Implemented

The Spacedrip device (see page 7 in attachment) is a container treatment plant that takes up the wastewater from a channel that flows through the Uhuru Park, Nairobi up to 50 m3/day and cleans it up so it can be reused for irrigation of the park. The system is handled with an automation software so it can be monitored and run up from a far distance and keeps a working order in every cases. This technology is not new per say, but it has a sedimentation tank in front of it. There is a biological part where organics and a bit of nitrogen are removed; then, a filtration unit that micro- filtrates out most of the bacteria; clean water enters a tank in a technical chamber and from there, it is filtrated by UV light and chlorine when necessary. So, water comes into the treatment plant from the stormwater drain channel and goes out the treatment plant through sprinklers in the park. Water arrives through a storm water channel. There are quite no rainy events there, but a lot of water coming from septic tanks and industrial site discharge, which is unknown and difficult to predict. This means that water flowing through is quite dirty, and direct use for the irrigation is not a good idea. However, following treatment, it becomes very clean from organics and bacteria. This technology has been used at the Uhuru Park for two weeks now.

Results Obtained

The commissioning went well a month ago (May 2023), and the system has been running in its full capacity for two weeks now. Currently, up to 25% of the necessary Uhuru Park irrigation water is coming from this treated wastewater device. The implementation of this device aimed to give a proof that this kind of system with sound automated plug and play technology works well. These compact units can be placed anywhere, even in small areas. It can run for a long period of time and is in a testing phase. The input and outputs analyze results are presented in Chart 2 (See Page 9 in attachment), with a 100% bacterial removal thanks to this technology. The influent and output picture shows the water obtained is quite pure. However, it is not safe enough to be consumed and is only for irrigation purposes.

Conclusion

This kind of system is same with Seehausen (Germany) water reuse systems. But this is a smaller unit that is quite compact, and which can be placed in small areas or bigger city centers where the wastewater is reduced. The water obtained can be used for toilet flushing or garden irrigation and there is no need for building new infrastructure to use it. Thanks to the IT Solution enabling the distance monitoring, there is no need to go on site for maintenance.

Therefore, it is possible to predict the maintenance of the system, that will allow it to run for a long time and avoid breakdowns. Pictures of some small three-meters containers are presented in Page 10 (See attachment); these are devices with showering and toilet units that were produced by Spacedrip for military projects, and which can be placed anywhere for continuous reuse of water.

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The Way of Bremen-Seehausen to an Energy Neutral Plant

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During the 6th edition of Ask The Experts series themed: “Valorising the end-products of domestic and industrial wastewater treatment” organized on April 25th, 2023, by the African Water and Sanitation Association (AfWASA) with the German- African Partnership for Water & Sanitation (GAPWAS), the collaboration between the cities of Windhoek in Namibia and Bremen in Germany was highlighted.

Indeed, Windhoek and Bremen cities began a collaboration in year 2000 from a long historical relationship including the support from Namibia struggle for independence. In 2013, the two partners joined the municipal climate partnership project, continuing the tradition of knowledge sharing. The project mainly prioritized the solid waste management, wastewater management and provision of basic sanitation services for informal settlements in a quest to contribute to the United Nations Sustainable Development Goals. The city of Windhoek and Seehausen started collaborating in 2018. This knowledge- based collaboration focused on issues mainly pertaining to wastewater treatment. The team usually meets on a monthly basis to discuss and analyze different topics, seeking for solutions and improvements.

The collaboration approach over the past couple of years focused on exchangeable visits in Nambia and Bremen on topics of common interest. For example, the two charts on variation in influent flowrate (see Attachment, Page 3) show the hourly influent volumes of Seehausen and Gammams plants, and the hourly organic meta concentrations. For both plants, the factor between the minimum and maximum daily figures is about 0.5. But there are some differences between the trends or the hourly patterns per day, which could be due to the travel time of water to the plant, which can differ. In Bremen, there is also a storage capacity on the pipelines. The patterns could also be different per hour of a day due to industrial and domestic waste. Indeed, Gammams in Whindhoek only takes water of domestic origin, while Bremen takes wastewater from domestic and industrial origin, considering that industrial waste is very hard to predict. Also, in Namibia there is only a separate sewer system, meaning that most of the infiltration is diverted into rivers, while Seehausen in Bremen has both the combined and a separate sewer. These are all important factors, among others that can be used to troubleshoot or rectify faults towards improvement and to plan optimization to ensure process efficiency.

This gives few insights into the actual cooperation which aim to get more knowledge on the whereabout of our carbon and what it can be used for. In one of the Bremen treatment plant balances (see Attachment, Page 4), we can see the quantity of carbon which is transferred to the Bio reactor, and the quantity which is brought to the digestion. Biogas is derived from that, and with a combined heat and the power plant from which energy can be produced. So, every optimization of a treatment plant, can change the future. The results at the end of the treatment process should be the possibility to produce more energy and gas, or the use of carbon for denitrification to get a better affluent quality of treatment plant. Exchanges with laboratories that make the analyzes and other partners of the wastewater sector revolves around similarities in operations and special tasks as well to identify what can learned from each other. For example, Windhoek has a 50 years’ experience in removal of micropollutants and climate change adaptation. Bremen can learn this know-how from Windhoek, especially since Bremen is getting more and more dry; natural water bodies get increasingly smaller, and the city has to think over how to use water and what for. For example, Bremen uses semi-purified water for gardens or public places just like Windhoek. On another realm, Bremen has been preparing for rainfall events for the last 30 years, and this is something Windhoek may learn from Bremen.

Bremen’s biggest wastewater treatment plant is Seehausen, and there is a process to get an energy neutral plant. Bremen is a city in the northern part of Germany, and the responsible for city sanitation is hanseWasser, operating on a public- private partnership model. The Bremen area is very flat; consequently, more than 200 pumping stations are needed to pump every drop of wastewater against gravity to the treatment plant in Bremen Seehausen located in the highest (1012 meters higher than the rest) region of the city.

The treatment plant in Seehausen had about 1 million inhabitants connected, and the wastewater treatment plant in the northern part of Bremen had about 160,000 inhabitants connected. The presentation (see Attachment, Page 8) highlights a very good development of the self-production of energy, with two (2) big steps between 2010, 2011 and in 2013. The first step was the introduction of a new wind turbine, and in 2013, the combined heat and power plant station was renewed; this allowed the generation of more energy from the gas available. In 2022, the self-production stood at 130%, with about 100% from the combined heat and power plants and 28% from wind turbines. It rains very often at Bremen, and the city can only generate around 1 to 2% of energy from self-production. The city didn’t only focus on the production, but also on reduction of the total energy consumption of the plant, with a drop of about 25% over the years with optimization and a new aggregate.

The specific energy consumption per inhabitant is also an indicator for the reduction. Bremen’s way to energy neutrality is based on three pillars:

  • The first one is the repowering. Three (03) combined heat and power units were renewed. Every unit is around 1.4 megawatts electric per unit, and a wind turbine (see Attachment, Page 9). What comes from the combined heat and power plant can be used to improve the gas production.
  • Some projects are also ongoing to have a higher gas production, including a demand reduction in a technical way by specific reinvestment. It was also economically viable to get new aggregates with the lower specific demand. For example, in this case a compressor hall with seven (7) Compressors for the appropriation of in-house processes.
  • The third pillar is optimization. There is a digital twin of Bremen’s treatment plan for all biological processes. This allows for optimized process, and especially the aeration, the quantity of oxygen needed for the microbiology part. Some set of DWA A- 216 rules described in the presentation (see Attachment, Page 11) can also be used to view how much energy is needed, and if there may be a possibility to reduce it a little bit more (how to do an energy check, an energy analysis for wastewater treatment plant in Germany, with guidelines through the whole calculation process). An energy analyzes enables to see the best value that can be reached for specific energy demand for the treatment plant, with a highlight on the quantity of energy that can possibly be reduced in future projects.

The presentation (see Attachment, Page 12) showcases parts of set rules, with specific energy consumption of the whole treatment plant. The total energy demand of the plant is known, as well as the number of inhabitants connected to the plant; this allows to calculate the specific energy demand in kw/hours per inhabitant and per year; getting inside the benchmarking system of this set of rules allows to find the frequency of lower deviation and understand the self-monitoring system of energy of a plant. The presentation (see Attachment, Page 13) also highlights the results of energy analyzers from the plant, with the best values that the plant can reach over the year. Bremen-Fargo is a bit far away from this added value and must figure out how to make the treatment plant better in energy consumption.

To sum up, the project started at a good point because of lot of aggregates for energy production, and high demand of energy had to be renewed. A company-wide goal was set to get energy neutral for the whole company; this allowed to reduce the specific demand of aggregates and raised the production efficiency.

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Wastewater: A valuable Resource

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As part of the 6th edition of Ask The Experts series themed: “Valorising the end-products of domestic and industrial wastewater treatment” organized on April 25th, 2023, by the African Water and Sanitation Association (AfWASA) in collaboration with the German- African Partnership for Water & Sanitation (GAPWAS), Justina Haihambo, Process Engineer Gammams Wastewater care Works at the City of Windhoek, central area of Namibia gave an insight into Windhoek’s direct potable reclamation.

Windhoek is located in Namibia, the driest country of sub-Saharan Africa, and is also the hub for the country’s economic, industrial, academic, commercial and political activities. The mission of the City of Windhoek is to enhance the quality of life of the population through efficient and effective municipal services and to improve water security. In the last housing and population census, the population of Windhoek was forecasted at 341000 people, but currently at a growth rate of 4.3%, is forecasted at about 441700 people. The annual water consumption of Windhoek is 27 000 000 m3/year, with an annual increase of about 3%. This, coupled with factors below, make the provision of water security of Windhoek uncertain:

  • Windhoek has the highest population growth rate that increases the water demand proportionally;
  • Windhoek is also synonymous for irregular or erratic rainfall patterns, which result in the lowest average rainfall, for annual rainfall of about 300 to 400mm. A low annual rainfall with the high annual evaporation of about 3000 to 3500mm;
  • Windhoek experiences regular drought and the ephemeral rivers that are closed to this city are fully exploited;
  • The perennial waters sources that are located closed to Windhoek are too far away. The Okavango River for example is 700km away, and the Atlantic ocean is about 3500km away.
  • The main perennial rivers are national borders originating in the neighboring countries, which means that the long- term agreement on water exploitation cannot always be guaranteed;
  • The portable water sources closed to Windhoek in close proximity have been fully harnessed.

The timeline of the potable water supply scheme of Windhoek has to be understood and considered in other to aid in understanding how wastewater is or has become a valuable resource toward water security. So, Windhoek was settled in 1840 partly because of the availability of groundwater from permanent hot springs. Until 1960, the city continued to heavily rely on groundwater from a well field for its water supply security, despite the construction of two small state-owned dams build-in ephemeral rivers in 1993 and 1958 respectively. So, meanwhile the population continued to rapidly increase, the city continued to experience regular drought in parallel. Consequently, all water resources at the time became depleted, which made the future of water security uncertain. Heavily relying on too small construction dams in ephemeral rivers and groundwater for water supply led to the fact that in terms of water, Windhoek became vulnerable; thus cementing the idea of unconditional water sources and supply and the idea of direct potable reclamation as well. This led to the construction of a direct potable reclamation plant in 1968 to argument the groundwater and the surface water supply, which at the time had become uncertain and unreliable. So, from 1970 to 1982, the state-owned supply system got extended in a three-dams systems.

From 1990 to present, Windhoek has been relying on what is known as the central area of Namibia supply scheme for its water supply or its potable supply needs. This supply scheme consists of the following:

  • First, the groundwater supply and the three-dams system, owned by a state- owned enterprise called NamWater, which is the country national water utility and bulk supplier;
  • Second, the reclaimed water or direct potable reclamation, with reclamation of potable water directly from sewage effluent that is produced and provided by a wastewater treatment plant called Gammams water care works wastewater treatment plant.

This direct potable reclamation was constructed at an initial capacity of about 4.8mega liters a day, which got increased over time. But at the end of its lifespan, in the midst of severe drought in 1997 and with lack of a sustainable water supply option at the time, it was decided to build a bigger plant at a capacity of 21 mega liters a day. Another Windhoek sustainable options to reduce the water demand, was the establishment of a semi- purified and irrigation supply scheme. This was established in 1993, with the construction of a dwell pipeline system to convey water from the old direct potable reclamation plant to sports fields of schools and establishment of businesses. This semi- purified water is also used at municipal wastewater purification plant for irrigation and general cleaning of equipment. This irrigation water supply scheme was established to decrease the Windhoek water demand by about 8%.

In another view, the current potable water supply scheme consists of:

  • Windhoek is indicated in the green square, central Namibia (See centre of Map 1 in attachment). So, the three- dams system that belongs to the state has the largest capacity; it consists of the Omatako dam (212 km from Windhoek) which is built in the Swakop river. Besides the rainfall, it gets supplemented by a scheme further up north and a state-owned scheme called Von Bach supply scheme from underground water; then the water is pumped into a canal called the eastern national water carrier located 430km away from Omatako dam, and which transports water to Omatako dam.
  • Then, the Von Bach dam is about 70km from Windhoek. So, water is pumped from Von Bach dam and is treated in the Von Bach purification plant; the water is then piped to Windhoek for supply. This water is finally blended with the direct potable reclaimed water and or the underground water for distribution.
  • The Swakoppoort dam (125km from Windhoek) is the largest one, which is built just downstream of the Swakop river.

Water reclamation or water reuse is known in theory as one of the main alternatives to reduce water demand. Therefore, Chart 1 in the presentation attached shows the annual consumption of water demand by source for Windhoek for the past 55 years. So, in general, the introduction of the direct potable reclamation means that the volume of water required from other conventional sources is reduced, and especially with introduction of the irrigation supply scheme in 1993. Direct potable reclamation also means that in normal metrological conditions, the groundwater can be preserved for use sustainably when necessary; for example, as was the case during the 2013 to 2019 drought, and more notable in 2019 when Windhoek experienced “the worst drought in 90 years” with the lowest average rainfall recorded.

Over the years or the 55 years, the water demand kept increasing proportionally with the growth rate; however, there were some notable reductions in water demands, and the weight of droughts in 1982-1983, 1996-1997, 2013-2019 were mostly attributed to water demand management.

Importantly, the ongoing success of direct potable reclamation can be attributed to correct practices and efficient operations for wastewater treatment. Therefore, if we don’t have efficient wastewater treatment in place, we don’t have direct potable reclamation. Grammans Water Care Wastewater treatment plant is an important component of the ongoing success of direct potable reclamation.

Grammans Water Care Works is a biological wastewater treatment plant that was built between 1959 and 1961 but commissioned in 1963. It was constructed with the initial capacity of 9 megaliters a day, which increased to 25 megaliters a day, its current capacity. It was designed to treat water from domestic origin. The industrial wastewater is diverted to another plant mainly to protect the direct potable reclamation plant from hazardous waste.

This allows to plan for Windhoek and the country, and Gammans serves as an important link in the water circle because it treats water, which is directly reclaimed for potable use, which serves partially towards meeting the water demand of the Windhoek potable water needs.

Chart 2 (see attachment) shows in- flow water into Gammans and then the supply water to the reclamation plant, and the product works into the reclamation plant. Of the effluent water received at Gammams, 75% is supplied to the direct potable reclamation plant. Of the water that is supplied, 85% is the direct potable reclamation plant intakes. of the intake, 92% is produced and then blended with other conventional sources for distribution.

With water reuse being recognized as the main alternative to reduce water demand or water consumption, Namibia as a water-stressed country must find ways to take advantage of all the drops of wastewater to increase the reuse potential. Therefore, another direct potable reclamation project was identified as one of the medium-term interventions to upgrade or improve water security. But for this project to be feasible, additional upgrades are required for the Gammams wastewater treatment plant and another municipal plant, in order to ensure that there is sufficient water at the right quality.

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Commercialization of Wastewater Sludge Beneficiation

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Sewage sludge disposal has become a costly and environmentally challenging matter that requires an innovative approach. Agriman (Pty) Ltd is a South African based company with an international footprint that provides a complete value chain solution for the handling, processing and beneficiation of wastewater sludge to a commercially marketable fertilizer.

Depending on existing infrastructure and processes employed at a wastewater treatment works (WWTW), Agriman has developed the ability to migrate upstream in the process line to perform and manage critical functions related to the digesters and dewatering of sludge that have a direct effect on sludge quality. By means of accelerated solar drying, sludge is dried and stabilized before disinfection and granulation takes place. Once granulated the product is then blended with conventional fertilizer feedstock to customer requirements for agricultural use, effectively transforming a hazardous waste into a registered organic fertilizer that is safe for agricultural use.

The environmental, economic and socio-economic impact of the traditional disposal methods of wastewater treatment works’ sludge is not a sustainable solution. Authorities are also being pressured by laws and legislations that are phasing out the disposal of sludge at landfill sites. Provided that dewatered sludge can be dried cost effectively at a specific WWTW,  Agriman can provide a sustainable long-term alternative that can be implemented on a large scale to safely handle and process sludge to an organic based fertilizer. The trend towards sustainable farming practices creates a high demand for commercially available organic fertilizers to supplement chemical fertilizers. This demand is currently not being met.  The potential to commercially beneficiate wastewater sludge to a registered and approved agricultural fertilizer on a global scale has been shown by Agriman as a model that is economically viable for wastewater authorities, the agricultural industry and sustainable development.

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