CESP Africa provided a 25m3/h containerized ultrafiltration system to Thika sewage &water Co. LTD to provide clean water for the population around Kantafu Ngoliba market in Kiambu county. Our containerized system is contained in a 40ft shipping container meaning it is portable.
The water to be filtered is sourced from Chania river in the area. Pump stations from the river pump water to Kantafu market where the filtration system is located.
At the plant there is a pioneer tank installed by CESP Africa to store the raw water before it is treated.
Pioneer water tank to store raw water and the containerized ultrafiltration system.
The ultrafiltration system.
The water is received in the container with the ultrafiltration system. The water is pumped into a sand filter to get rid of suspended material in the water.
Pump
The sand filter vessel contains different grades of media to remove the suspended solids in t he influent.
Multi-media filter and bag filter vessels.
The water passes through a bag filter with seven different filters to further purify the water.
Another pump pushes the water to the ultrafiltration membrane. The water is then stored in a clean water tank before it is used.
Control box for the system and housing for the ultrafiltration membranes.
A multi-media filter is generally one grade of crushed rock gravel, two grades of garnet and one grade of anthracite filtration media. The crushed rock is used for supporting the filter media and also to provide even distribution of flow during backwash. The course garnet is used as an interface media between the crushed rock and the finer garnet. The top layer (and coarsest) filtration media is the anthracite.
When is a multi-media filter required?
A multi-media filter is suggested when the Silt Density Index (SDI) value is greater than 3 or when the turbidity is greater than 0.2 NTU. There is no exact rule, but the above guidelines should be followed to prevent premature fouling of filtering membranes (reverse osmosis or ultrafiltration).
The larger (but lighter) anthracite coal will be on top and the heavier (but smaller) garnet will remain on the bottom. The filter media arrangement allows the largest dirt particles to be removed near the top of the media bed with the smaller dirt particles being retained deeper and deeper in the media. This allows the entire bed to act as a filter allowing much longer filter run times between backwash and more efficient particulate removal.
Media cleaning through automatic backwash.
The filter media should be cleaned on a routine basis. The length of the filtering cycle between cleaning sequences is dependent upon how dirty the source water is. Typical filtering cycles are in the 6 to 12-hour range. However, some applications allow for a much longer cycle, or in some cases, a shorter cycle.
The filtering cycle is determined by pressure differential between the influent and effluent gauges. Once the difference is approximately 10 PSID the media should be backwashed.
It is recommended that a filter be cleans at least once a day, regardless of application or differential pressure. The cleaning sequence of a filter system varies from one step (for simple systems) to as many as twenty (for more complex systems.) Regardless of the complex nature of the system, all filters are cleaned by reversing the water flow inside the filters. After backwash, the bed is allowed to settle and re-stratify before a final rinse and then it is placed back into service.
The FRP vessel.
Structural Composite Pressure Vessels offer reinforced fiberglass construction for outstanding performance and durability. Available in capacities up to 1,600 gallons.
A multi-media filter to remove suspended solids after wastewater treatment.
This year marks the 52nd world earth day. Since its inception the day has been an opportunity to highlight areas where we as humans have taken advantage of our home, planet earth. Climate change is one of the largest issues facing humanity. While we have an opportunity to correct the past, the time for action is now.
Invest in the planet
This year the theme of the day is ‘Invest in our planet’. It is our opportunity to invest time, money, effort, innovation and passion to save our planet from climate change and its effects. All parties need to be involved in this effort. From governments, organizations to individuals.
Let’s do something about it.
Across the planet there are organized events happening on Earth day to ‘Invest in the planet’. In Nairobi there are numerous events happening, like;
Nairobi River Fall See Waterfalls Restoration Intervention – The target is to establish Green Tourism Destination by developing Nature Paths along the river, construct Gabions along the river banks, botanical garden at the waterfalls, engage organized groups working along the river to undertake Bamboo Growing Challenge – 120 Green Champions from 6 Villages in Lucky Summer Ward, Ruaraka Sub County, Nairobi County Kenya to produce 12,000 Bamboo Seedlings to be planted by 5th June 2022. The initiative is Led by Lucky Summer Environmental & Waste Management Organization with technical guidance from National & County Government, GKIT, KFS, NMS, Business Community, CSOs, CBOs, working in Environment Sector.
Mathare 4A ground Community Clean-up.
Refueling Africa : Ethical Investment in the energy sector in Africa with a key focus on EACOP and other spiraling fossil fuels investments – In this webinar, we will hear from community leaders fighting fossil fuels intrusion from different parts of Africa including Kenya, Okavango Delta, Uganda, Tanzania and Mozambique.
Among other events. To learn more about these events as well as ways to ‘invest in our planet’ in future visit the Earthday website as well as our own website.
Looking into the future.
The good news about the future is that there is still time to correct the current state of the planet. We need to reach net-zero greenhouse gas emissions by mid-century to keep the global temperature below 1,5°C. Though achievable, it will not be an easy task.
What can I do right now?
Bold, fast, and wide-ranging action needs to be taken by governments and businesses. But the transition to a low-carbon world also requires the participation of citizens.
The manufacturing industry is the biggest contributor of greenhouse gas emissions, and needs to play an pivotal role if real change is to be made.
The transport and energy industry are big players in the climate change.
The farming industry and food production will have to change.
Wastewater treatment aims to get rid of the contaminants in wastewater to produce clean effluent. There are different treatment technologies to achieve this end, here we will go through the activated sludge treatment process. The process uses bacteria that biologically digests the solid matter in the wastewater to leave clean effluent as a final product.
Flowchart of the activated sludge wastewater treatment process.
The flow equalization chamber receives the raw wastewater. A screen filters the raw wastewater going into the first chamber, large solid matter as well as material that can not be broken down by the system is filtered out. Undigestable material may include fabric, pads, surgical masks etc. Often issues in the wastewater treatment plant arise because of undigestable solid matter clogging up different stages in the treatment process (e.g. clogging pumps in the system) hence the screening process is very important.
The content and rate of flow into the system varies throughout the day hence this chamber aims to homogenize the wastewater as it goes into the system.
Anaerobic digestion.
The digestion process starts in this chamber. Bacteria breaks down the wastewater without using oxygen hence an anaerobic process. At this stage the bacteria breaks down the nitrogenous components of the wastewater.
Aerobic digestion.
In this stage, the effluent shall be treated in extended aerobic biological reactor. The system is designed for extended aeration mode where excess oxygen is provided for oxidizing the carbonaceous as well as the nitrogenous BOD present in the effluent.
The organic wastewater is introduced into a reactor where an aerobic bacterial culture is maintained in suspension. The reactor contents are referred to as the Mixed Liquor Suspended Solids (MLSS). In the reactor, the bacterial culture carries out the conversion in general accordance with the stoichiometry as under:
Reaction:
COHNS +O2 + NUTRIENTS –bacteria- CO2+NH3+ C5H7NO2+ other end products (Organic matter)
The aerobic environment in the reactor is achieved by the use of Mechanical Surface Aerators, which also serves to maintain the reactor contents in a completely mixed regime. After a specified period of time the mixture of new cells and old cells is passed into a secondary clarifier, where the cells are separated from the treated wastewater.
A portion of the settled cells is recycled back to the aeration tank to maintain the desired concentration of organisms in the reactor, and a portion is wasted. In this system due to the extended retention period in the reactor the bacteria enters into the endogenous respiration phase resulting in relatively simple end products and energy, stable end products are also formed. The endogenous respiration phase is represented by following equation:
Bacteria
C5H7NO2 + 5 O2 —————-CO2 + 2H2O + NH3 + energy
The effluent will then flow into the sedimentation tank.
Sedimentation
The effluent moves to the next chamber where it settles. Any remaining solid material settles to the bottom of the chamber. Clean water from the top of the chamber is flows into the next chamber.
Any solids that settle in this chamber are refluxed back to the anaerobic chamber where the solid matter is taken through the digestion process again. The material that settles at this stage also contains bacteria which can be reused to avoid need for constant repopulation of the bacterial in the system.
Middle water tank.
For systems that have additional filtration of the effluent, the middle water tank acts as temporary storage before filtration.
Sand filtration.
A sand filter removes any remaining suspended solids from the effluent.
Clean water tank.
The clean water tank stores clean effluent ready for use.
The effluent can be disinfected by adding chlorine.. Depending on local regulation the effluent may be drained away or used for irrigation, gardening etc.
A mid-sized activated sludge wastewater treatment system.
The activated sludge treatment process is a relatively simple, it is generally cheaper and easier to maintain. It can also be scaled up, from domestic systems to larger commercial systems.
Water is possibly the most important resource to man. It is integral to so many of our activities. After use, the water is contaminated and not readily usable in many cases. The wastewater produced from different processes is not contaminated to the same extent. Hence the different classifications of wastewater. Blackwater and greywater.
What is greywater?
Greywater, also called sullage, is wastewater from households or office buildings from streams without fecal contamination. All streams except for the wastewater from toilets. Sources of grey water include sinks, showers, baths, washing machines or dishwashers.
A kitchen sink is a source of greywater.
What is blackwater?
Blackwater is wastewater that contains feces, urine, water and toilet paper from flush toilets. The pathogens present in blackwater also distinguish it from greywater.
Blackwater being drained into a water body.
Why the distinction.
Though both may be wastewater the level of contamination is different, requiring different treatment.
Greywater is less contaminated than blackwater meaning treatment is simpler. Provided the greywater does not contain harmful chemicals such as soap and detergents it can be recycled for irrigation and other domestic uses. Organic matter from kitchens may provide an added bonus to plant life if used for irrigation.
Blackwater is more contaminated, meaning it requires more thorough treatment before it is fit for any other use.
Treatment processes such as extended aeration may be used to treat the blackwater to produce clean effluent. Chlorine may be added to the effluent to kill any pathogens present in the effluent.
A commercial sized wastewater treatment plant designed and installed by CESP Africa.
These systems treat both black and greywater together giving clean effluent that can be used for irrigation and general cleaning. The effluent produced is also fit for dumping in the local drainage after certification by National Environmental Management Authority (NEMA)
Conclusion
Blackwater and greywater should be stored and treated separately, where possible, to be more energy efficient. Households and offices that actively reuse greywater have the added benefit of reduced cost associated with water while also being environmentally conscious.
We supplied an 800 GPD (3,600LPD) reverse osmosis filtration system to a home in Nairobi county. The client was struggling with borehole water that discolored and had a large amount of suspended solids.
The control panel and a view of the overall system.
The client took a water sample thereafter had it analyzed and got the following results.
Borehole water analysis
PARAMETER
Values
KS EAS 12:2018*
WHO standards
Remarks
Colour (Pt. Co. APHA Colour)
561
50
15
Fail
Turbidity (NTU TUB)
83.1
25
5.0
Fail
Total Suspended Solids (mg/L TSS)
52
ND
NIL
Fail
Iron (mg/L Fe)
6.45
0.3
0.3
Fail
Manganese (mg/L Mn)
0.317
0.1
–
Fail
Ammonia (mg/L NH3)
1.7
0.5
0.5
Fail
BACTERIOLOGICAL ANALYSIS
Total Coliforms (cfu/100 ml TC)
37
ND
ND
Fail
Results from the water analysis
*The KS EAS 13:2018 specifies requirements for packaged mineral water for human consumption. This standard applies to natural mineral water, mineral water, natural spring water, spring water and carbonated mineral water.
The analysis confirmed our suspicions on what might be the main issues with the water. The dissolved iron and manganese were responsible for the colour of the water.
The findings led the design team to chose a reverse osmosis system, as it would remove all dissolved salts as well as any bacteria present in the water. A plant of 800GPD was chosen to match the needs of the household.
The plant also includes :
Multi-grade sand filter,
Greensand and DMI65
Activated carbon filters.
The three vessels in the system.
How the plant works.
Water from the borehole is pumped into a 5,000-liter raw water tank. A pump directs the water through the first vessel with a multi-grade sand filter to remove any suspended solids. The second vessel contains Greensand and DMI65 which remove iron and manganese in the water. The third vessel contains activated carbon to remove chlorine* in the water.
*The chlorine kills any bacteria and viruses present in the water.
The water is then passed through a PP, Granular activated carbon and CTO filter to further filter out any suspended solids, colour, odors and bad taste from the water.
Another pump then passes the water through the reverse osmosis (R.O) filter to remove any dissolved salts from the water. Finally, tan ultraviolet filter kills any remaining pathogens in the water.
A 5,000 liter tank stores the now filtered water, ready for use.
Raw borehole water and clean water after filtration.
Maintenance
The system is set to periodically backwash the 3 larger vessels, this prevents the filters from getting clogged with suspended solids and other contaminants in the water.
The R.O. filter is periodically backwashed to prevent it from clogging. The system is also set to automatically dose anti-scallant to prevent any buildup on the R.O. membrane.
The PP, Granular activated carbon and CTO filters are replaced as needed.
More than 13 million people in Kenya and the greater horn of Africa region are at serious risk of starvation says the World Food Programme (WFP).
In recent years Kenya has received poor rainfall. Three rainy seasons have brought below average amounts of rainfall bringing us to the current situation. The March to May long rains are also forecasted to be lower than average.
The lower rains have already resulted in lowered livestock population and crop coverage.
“Available field assessments and key informant estimates suggest household herd sizes are currently 30-50 percent below baseline levels, implying that most pastoral households are entering the January to March 2022 dry season with fewer resources than they had before the peak of the 2016/2017 drought”
Rainfall in previous seasons ended prematurely meaning yields were reduced by 40-80%.
The National Drought Management Authority, in its monthly report, compared the national crop coverage between December 2020 and December 2021. Arid and Semiarid areas of the country are already in drought.
Crop coverage compared between Dec 2020 and December 2021.
Many areas in the country are also at risk of reduced crop and livestock production.
WFP is asking for $ 37 Billion to make the communities to be affected by the drought more resilient and ready for the drought. If not met this could spell a drought much worse than that experienced in 2007.
A septic tank is a tank typically placed underground, in which Settling and anaerobic processes reduce wastewater (solids and organics). Typically, septic tanks are made of concrete or are ready to install plastic tanks. Though their treatment efficiency is only moderate.
Septic tank systems are a type of simple onsite sewage facility.
Mistakenly, the term may be used to refer to a wastewater storage tank or a biodigester. These two are different and serve different purposes. A wastewater storage tank doesn’t treat the wastewater but only acts as a temporary hold before it is transported away. A bio-digester takes advantage of aerobic processes to more effectively break down the wastewater to give clean effluent.
Septic systems are also called:
onsite wastewater treatment systems,
decentralized wastewater treatment systems,
cluster systems,
on-lot systems,
individual sewage disposal systems, and
private sewage systems.
How it works.
Septic tanks usually comprise of one or two Large chambers depending on the needs of the people it serves.
A schematic of a septic tank.
The first chamber receives the wastewater and regulates its flow. The solid waste, being heavier, sinks to the bottom of the chamber. The liquid portion of the wastewater fills the first chamber until it reaches the inlet into the second chamber. The same happens in the second chamber until it fills the chamber. At the liquid then leaves the septic tank through an out let into a soak pit.
The fats and oils float on top of the liquid portion of the wastewater to form a layer of scum. The solid waste settles at the bottom of the septic tank’s chambers forming a sludge.
There are bacteria in the wastewater that anaerobically digest a portion of the waste. The rate of digestion is slow hence the sludge needs to be periodically emptied.
The soak pit is a covered, porous-walled chamber that allows water to slowly soak into the ground.
Considerations when choosing a septic tank
Size the system will occupy.
The size of the system is dependent on the number of people expected to use the system. Typically, the breakdown of wastewater in the septic tank is slow so it has to be dug deeper, than say a biodigester. Some may even be up to 7 meters deep.
Emptying the system.
The breakdown process is slow because the system only utilizes anaerobic processed, hence sludge usually accumulates in the tank.
Periodically the system will have to be emptied out using an exhauster or vacuum truck.
The soak pit.
The soil has to be able to soak up the liquid portion of the wastewater after the septic tank or stand the chance of saturating the nearby soil. This could form puddles of wastewater on the surface or in extreme cases collapse of the soak pit.
Why use a septic tank?
It might be your only option.
Many areas within Kenya, especially rural areas, do not have access to government provided wastewater treatment facilities. When faced with such a situation getting a septic tank to partially treat and hold waste water might be the only real option you have.
Public and environmental health.
Some more impoverished parts of the country that lack proper wastewater management systems resort to dumping their sewage, which is a huge public health and environmental risk. As a solution, one could use a septic tank to hold their wastewater.
What are my options?
When the local administration hasn’t provided a wastewater disposal solution your main options are a septic tank or an aerobic wastewater treatment system. The latter having its own advantages and considerations over a septic tank.
The county government is in the process of building a major water project to service the area. The water shortage in the county has been grave to a notoriety level and that has got the attention of the national government, which for the last four years has vowed to increase water access and sanitation services in every corner of the country.
The project has been divided into three phases. The first already completed in August 2021. True to its promises, the national government in collaboration with local, national, and global partners has aggressively embarked on the implementation of water projects in the most drought-hit and water shortage hotspots in Taita Taveta.
The three-phase project is set to cost a whopping USD $414 400 (approximately Sh47 million) already secured from National Treasury and aims to support a 1, 000-hectare irrigation project as well as supply domestic water to 7,000 people and 15,000 livestock.
“The project is looking to harness Lake Challa water resource for both domestic and irrigation use for the areas of Mwatate, Voi, and Taveta,” said Dr. Keinan.
Nation wide
On Friday last week, yet another water project funded by the European Union through the national government’s Water Sector Trust Fund was commissioned at Maktau.
The Sh88 million Nyangoro-Maktau Water and Sanitation Development Project will serve a population of 17,000 residents from Maktau and Godoma locations, who had to walk long distances in search of water for domestic use.
Other small-scale water projects have also been launched by the national government in partnership with the county government and continued to shift the landscape of water access and sanitation.
Kenya’s water sources are unevenly distributed and at times plagued with community conflicts that further increase water access distress, especially among arid and semi-arid regions.
To quell conflicts, the national government is using the strategy of public participation in the spirit of developing water projects anchored on prudent sharing for the benefit of all, which are now bearing fruits in Taita Taveta and other water-distress regions.
In March of 2020 the first case of COVID-19 was reported in Kenya. Along with being a global pandemic it also brought the issue of bio-hazardous waste associated with protective gear. National Environment Management Authority (NEMA) put in place guidelines to guide the handling and disposal of these hazardous material, but in a recent report NEMA says this waste is being improperly managed.
The guidelines were put in place in accordance with the Environmental Management and Coordination (Waste Management) Regulations of 2006, which has provisions for handling and disposing of Biomedical waste. The guidelines are to protect those handling the waste as well as the general public from COVID infection.
Hospitals and other medical facilities are more prepared to handle such waste, it is the general public that is the main culprit in mishandling biomedical waste.
Officials, garbage are helping each other to transport garbage bags to the store.
Their application is in the form of;
a) In gated community, apartments, residential areas, factories, institutions, office blocks, the management or the owner of such facilities will provide medical waste pedal bins that will have biohazard bin liners. The management/owners will engage a licensed hazardous waste handler to collect and transport the infectious waste for a final disposal in accordance Environmental Management and Coordination (Waste Management) Regulations of 2006. Hence forth referred to as – EMC (Waste Management) Regulations of 2006.
b) In the rural and small urban centers at the ward level, the County Governments shall provide the same waste bins as in (a) above that will be placed either at the Chiefs Camps, ward offices, or health clinics and any other appropriate designated places that will be communicated to the public. Collection of such hazardous waste from such designated places shall be done through a licensed infectious waste handler.
c) In the public places including markets, bus/ matatu terminals, the county government shall provide to the general public Covid-19 related medical waste pedal receptacles that will have biohazard bin liners installed strategically in the public places and well secured and labelled infectious waste. Each of the county government shall engage a NEMA Licensed infectious /biomedical waste handler as required by EMC (Waste Management) Regulations of 2006.
d) If no special garbage bins are available, residents could spray disinfectant on both sides of their used masks with recommended disinfectants and fold them up before putting them into a sealed bin liner in the dustbin.
GUIDELINES FOR WASTE COLLECTORS
• Handle carefully all biomedical waste to avoid spillage of the same on the road/Highways during transportation.
• Ensure regular sanitization of workers involved in handling and collection of biomedical waste.
• Workers shall be provided with adequate PPEs, including three (3) layer masks, splash proof aprons, gowns, nitrite gloves, gumboots and safety googles.
• Use a dedicated vehicle to collect COVID-19 ward waste.
• Vehicle should be sanitized with sodium hypochlorite or any appropriate chemical disinfectant after every trip.
