A smart solution for preventing environmental pollution caused by overflowing onsite sewage septic tank

Abstract

An innovative remote sensing device for the detection and monitoring of sewage levels in underground onsite septic tank is developed. The overflow of underground onsite sewage septic tanks located around buildings for the collection and disposal of wastewater is hazardous to the environment releasing infectious pollutants and obnoxious contaminants. The inability to accurately determine the level of the sewage in the underground septic tank most times causes overflow of sewage into the environment without the knowledge of the users of the facility. A smart onsite sewage septic tank level monitoring device is developed enabling the users of the facility to promptly detect when it malfunctions to plan ahead for the evacuation in order to prevent the overflow. The device implements ultrasonic sensor to detect and monitor level of the wastewater in the septic tank and a Global System for Mobile Communications (GSM) module to send short message service (SMS) to the enrolled users’ mobile phone numbers and the sewage evacuation agents. A test run conducted showed response time within 30 s. The developed device is suitable for low income countries of Africa.

Highlights

• •Remote sensing of On-Site sewage septic tank levels is introduced.
• •The developed device uses ultrasonic sensor technology for detection of sewage levels.
• •The data on septic tank levels is transmitted online via GSM module to the enrolled evacuation agents.
• •The efficacy of the developed device was validated through field test on sewage septic tank.
• •Developed device is low cost, uses solar power, and is suitable for Africa.

1. Introduction

This paper focuses on creating a solution for the onsite sewage system which is the most popularly used in developing countries, to address the causes of overflowing of underground septic tanks leading to contamination of shallow water wells. The severity of the hazard caused by the overflowing of the onsite sewage septic tanks can be seen at the hospitals and medical clinics where toxic wastewater from patients suffering from cholera and other viral infections may be discharged into the environment through the overflowing septic tank [[1], [2], [3]]. This can lead to epidemic of infectious diseases for the consumers of the untreated contaminated table water from shallow wells. Sewage refers to wastewater and excrement conveyed in sewers. These include waste matter such as water or human urine or solid waste, faeces or dirty water from homes which flows away through sewers. Sewage also includes faecal sludge which refers specifically to a mixture of human excreta, water and solid wastes such as toilet paper or other anal cleansing materials conveyed in sewers. Inside the onsite septic tank, sewage is separated into three components, liquids which are the effluents, solids or sludge that settles to the bottom of the tank, and grease and other scum that floats to the top. Domestic sewage containing heavy metals from body lotions, skin cream, and poisonous substances discharged in the septic tanks can be passed into the environment during overflow of the facility [4,5]. It is therefore imperative that the level of sewage in the septic tank is monitored to ensure prompt evacuation when about getting filled to prevent it from overflowing. The design of the onsite septic tank is such that it does not overflow when functioning properly and with periodic frequent evacuation usually every three years or less depending on the capacity and the estimated quantity of sewage inflow. However the septic tank can overflow due to damaged or blocked plumbing, backflow from the sewerage system, a damaged septic tank or as a result of flood water levels above the outflow pipe. A prototype smart sewage system is developed which implements a remote sensing technology to accurately determine the level of sewage in the septic tank and also alerts the users for the prompt evacuation of the facility to avert overflow. The developed technology is targeted at mitigating the pollution from overflowing onsite sewage tanks and creating an efficient process that will enable effective treatment of the wastewater through prompt evacuation plan.

Onsite septic tank systems sometimes implemented with soak-away pits are usually adopted in most buildings at low income countries of Africa because of their affordability and ease of construction according to previous reports [6,7]. Underground septic tanks are evacuated periodically, with the sludge removed to a central location where it is treated, recycled, and the waste discharged in an environmentally safe manner [8,9]. Buildings constructed to accommodate large populations such as schools, hospitals, public offices, etc., which use underground sewage septic tanks require frequent evacuation to avoid overflowing into the environment. The sewage septic tanks are underground making it difficult to promptly detect when it malfunctions and to predict when it will be filled with the collected sewage. Also the pathways to the agents responsible for the evacuation is not always promptly available [10,11]. Consequently, the sewage septic tanks are most times filled and overflow into the environment causing the pollution of the premises and spread of infectious contagious diseases [[12], [13], [14]]. The situation is very common in Nigeria, Ghana, Kenya and other countries in Africa where onsite sewage septic tanks are prevalently used. The numbers of occupants in buildings in such locations exceeds the normal capacity and are characterized by dense overcrowded population which makes them vulnerable to the adverse effects of overflowing septic tanks.

It is hazardous to allow untreated sewer to overflow into the environment. The negative impacts of sewer overflow can be seen on its adverse influences on drinking water, available surface waters, recreational and resort beaches, irrigated vegetables and groundwater [15]. Sanitary wastewater from buildings and sewage from hospitals and health clinics are environmental reservoirs of most microbial pathogens. Most worrisome is that sewage wastewater contributes up to thirty one percent of public health issues in the environment, topping the chart on the impact of sewer overflow on public health as shown in Fig. 1 [16]. Other causes of overflowing sewer include sewer leakage, faulty or busted sewer pipe joints, and malfunctioning sewer network operations.

Fig. 1.

The estimated impact of sewer overflows on public health.

Poor management of sewage disposal can lead to coastal pollution and transmission of hepatitis A virus (HAV) and other infectious diseases [17]. Generally wastes such as heavy metals, detergents, human wastes, pesticides and organic matter are accumulated in sewage wastes. In developed countries, sewage disposals are in underground channel systems where they are treated and recycled [18]. The underground channel central system is complex and capital intensive and therefore unattractive for low income countries of Africa where buildings are poorly planned. Consequently most African countries rely on the onsite sewage septic tank which frequently overflows to the environment spreading contaminants and diseases. The main cause of the overflowing onsite septic tanks during the malfunctioning of the facility has been identified to be the inability to monitor the sewage levels since the tank is usually concealed underground. Thus, the motivation of this research which developed a simple, low cost remote sensing device for the detection of sewage levels in the onsite septic tanks.

2. Materials and methods

The conventional underground sewage septic tank is described in Fig. 2. The T-shaped or elbow shaped inlet pipe is provided at the upper portion of the septic tank towards the source of the sewage while the outlet pipe also T-shaped is located towards the effluent outflow usually at about 250 mm below the level of the inlet pipe. Lighter materials such as scum float at the top while heavier particles sink and settle as sludge at the bottom. The liquid materials described as effluent are discharged through the outlet pipe to the effluent drain-field. Gases escape through vent placed at building top height. The available openings to access the septic tank are the Access riser or manhole, and the inspection access or inspection access pipe. The freeboard is the gap between an upper slab of septic tank and liquid level usually about 30 cm. This freeboard depth is what the remote ultrasonic sensor measures to detect an abnormal rise in the sewage levels to avert overflow of the facility.

Fig. 2.

The operation of onsite sewage septic tank.

A remote sensing technology is positioned at the septic tank inspection access hole applying the ultrasonic sensor to monitor the level of the sewage. The operation of the remote sensing of onsite sewage septic tank level is presented in the block diagram in Fig. 3. The schematic diagram illustrating how the smart septic tank system detects the sewage level is shown in Fig. 3. Solar power is a preferred electric source because it is very reliable, stable and renewable, however locations with better electric power solutions can modify the power source to suite them.

Fig. 3.

Block diagram of the operation of the remote sensing of onsite septic tank level.

2.1. Power supply to the device

A 160W 12V silicon monocrystalline solar module provides the power source for the device. The solar panel can be mounted on the roof of the building or on a pole as shown on Fig. 4. The maximum current that can be realized from the solar cell is calculated using equations (1), (2).

$$\mathrm{P}\mathrm{o}\mathrm{w}\mathrm{e}\mathrm{r}=\left(Current\times Voltage\right)$$ (1)

$$160\mathrm{W}=\left(Current\times 12V\right)\mathrm{C}\mathrm{u}\mathrm{r}\mathrm{r}\mathrm{e}\mathrm{n}\mathrm{t}=13.3\mathrm{A}$$ (2)

In consideration of an alternating current (AC) source, a rectifier circuit consisting of two pairs of diodes in a bridge configuration and a filter circuit using capacitors and resistors in pie circuit is used for the conversion to a direct current (DC). Although the AC voltage from the mains is 220V, a transformer is used to step it down to 12V before the rectification. The rectification circuit is not required if a solar cell is used since it delivers a DC current. The DC to DC converter is used to convert the direct current from the solar module from one voltage level to another.

Fig. 4.

The smart sewage system powered by the solar cell detects the sewage level in the septic tank and sends the data via GSM module to the enrolled mobile phone numbers.

The application of solar power or any other renewable clean energy sources are preferred since they reduce the emission of toxic gasses. Here we adopt a solar module technology with the mono-crystalline solar cells because they have higher incident photon to electric current conversion efficiency compared to the polycrystalline solar cells. The mounting of the solar panel was done in a location and position that allowed maximum sun rays on the solar panels.

2.2. Septic tank level detection

The ultrasonic sensor architecture was implemented in the detection of the sewage level in the septic tank. The HC-SR04 ultrasonic sensor operates on 5V and can detect distance up to 13 feet making it suitable for the developed device. It has the ability to function with a high penetrating power that can detect external or deep objects which makes it the ideal technology for detecting sewage level in onsite sewage septic tank [19]. Acoustic waves can penetrate transparent or colored objects and can be used in dark environment as applied in underground onsite septic tank. However, they are affected by foamy materials which deflect the acoustic waves at the interface. The HC-SR04 ultrasonic sensor comes with four pins namely the voltage common collector (VCC), Trigger, Echo, and Ground. It is interfaced with Arduino and it delivers 8 pulse pattern ultrasonic waves while in use. During operation the ultrasonic sensor transmits sonic signals which reflects back part of the emitted waves upon impact with a surface and is received by the receiver. The distance is then calculated bearing in mind that the generated ultrasonic wave signal undergoes twice the covered distance in making the to and fro movement from transmitter to sewage level and sewage level to receiver. The relationship between the speed and time of the generated signal is described in equations (3), (4).

$$\mathrm{S}\mathrm{p}\mathrm{e}\mathrm{e}\mathrm{d}=\frac{Distance}{time}$$ (3)

$$\mathrm{D}\mathrm{i}\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{n}\mathrm{c}\mathrm{e}=\left(Speed\times time\right)$$ (4)

The rated speed of the acoustic waves emitted by the ultrasonic sensor is about 330 m/s so the distance is derived from the time taken between the transmitted signals and the received signals. The actual distance is obtained by dividing the given distance by two since the signal reflects back to origin.

Care was taken while mounting the device at the access inspection hole of the septic tank to ensure that there can never be any contact with the sewage in the septic tank. The ultrasonic sensor is positioned with the diaphragm pointing inside the septic tank enabling the generated acoustic waves to travel vertically inside striking the surface of the sewage water and then reflected. Usually the housing of the ultrasonic sensor is made with high enclosure ratings to withstand fog and wet places. However the ultrasonic sensor may damage with water intrusion due to failed seals. In order to prevent the leakage of the seal, a Fluorocarbon sealant is applied which also protects the device from corrosion. The lifespan of the ultrasonic sensor is between 15 and 20 years.

The Ultrasonic sensor is coupled to the smart septic tank circuitry as shown in Fig. 5. The microcontroller controls the performance of the ultrasonic sensor.

Fig. 5.

The circuit diagram of the smart septic tank system.

2.3. The microcontroller of the device

The Arduino UNO board based on microcontroller ATmega328 was used in the smart septic tank device to interface the ultrasonic sensor with the GSM module. The microcontroller controls the performance of the ultrasonic sensor and converts the analogue data to digital signal and transmits same to the GSM module. The GSM is enabled at two stages, first, when the septic tank freeboard depth is twenty percent full, that is the freeboard vertical height reduces by 6 cm and second, when the septic tank freeboard depth is Eighty percent full, that is the freeboard vertical height reduces by 24 cm. The Arduino UNO differs from all preceding Arduino boards in that it does not use the Future Technology Devices International (FTDI) Universal Serial Bus (USB)-to-serial driver chip but rather uses ATmega328 programmed as a USB-to-serial converter. The advantage is that it incorporates its own USB boo-loader allowing experts the opportunity to re-program the microcontroller. Also the Arduino offers a large support community together with circle of funding libraries and hardware add-on shields. The code and programming of the microcontroller is available upon request from the corresponding author.

2.4. The GSM module used in the device

The SIM900D Module was implemented in the smart septic tank for the transmission of the generated sewage levels to the enrolled mobile phone numbers. A registered (subscriber identity module (SIM) card is inserted in the SIM900D module during operation. The SIM900D is suitable for this purpose because it is a miniaturized cellular module with the capability of General Packet Radio Service (GPRS) transmission, sending and receiving short message service (SMS). Also the low cost and small fingerprint and quad brand frequency support makes it a perfect solution for a long range connectivity as required in the smart septic tank. The SIM900D Module is described in Fig. 5.

2.5. Output SMS text message generated by the device

The smart septic tank delivers SMS message when the septic tank freeboard depth is twenty percent full, that is the freeboard vertical height reduces by 6 cm and second, when the septic tank freeboard depth is Eighty percent full, that is the freeboard vertical height reduces by 24 cm. The microcontroller was programmed to receive data from the ultrasonic sensor at the two levels and trigger the GSM module to send text message to the enrolled numbers. At 20% level, the message delivered is, “Attention! The Septic Tank is malfunctioning, the sewage level is rising”. Similarly, at 80% level, the message delivered, “Attention! The Septic Tank is full”. The 20% difference allows the pathway for the evacuation of the septic tank to be executed before the tank overflows. The fixed threshold for the device to activate and send a message is user defined. So the device can be programmed to function at 30% level and 70% level depending on the user's choice usually based on the estimated response time for the evacuation of the septic time.

2.6. Cost of the developed smart sewage system

The cost of the smart sewage system is relatively very low compared to other existing variants enabling the device to be affordable to low income countries of Africa. The device does not rely on internet for operation but it uses a GSM module to transmit data remotely. The cost of the developed device is presented in Table 1. All the electronic components were procured from HUB 360, A7 Oshodi street, Shop Number EU2 9 and 10, Lagos, Nigeria.

Table 1.

Costing of the smart sewage system.

Item	Quantity	Unit cost ($) USD	Cost ($) USD
Ultrasonic sensor (HC–SR04) China	1	5.99	5.99
Arduino UNO board (China)	1	10.05	10.05
ATmega328 microcontroller (China)	1	7.99	7.99
GSM Module (SIM900D) China	1	8.99	8.99
Solar module (160 W, 12 V) Comet series (Germany)	1	105.00	105.00
Plastic Casing for Packaging the device (China)		5.57	5.57
PCB board (China)	1	0.5	0.5
SIM card - Huawei (China)	4	0.99	3.96
Wire and other accessories		5.00	5.00
Total			$153.05

3. Results

Text messages has been used for various interventions especially in health and other industries but the service sometimes fails or are delayed due telecommunication network issues. The effectiveness of the GSM module was tested to confirm the reliability of this solution by enrolling two mobile phone numbers within Lagos, Nigeria on the device. A bucket was used as a prototype septic tank to test the developed device by positioning the device on the lid of the bucket and gradually letting water flow slowly into the bucket. A meter rule was used as a dip stick gauge to monitor the level of the water in the bucket as the water flowed inside the bucket. The developed smart septic tank device was programmed to detect the level of water in the bucket at 20% which corresponds to a measured vertical height of 0.6 cm on the dip stick gauge. Also, it was programmed to deliver another text message and at 80% full which corresponds to vertical height of 24 cm on the dip stick. During the test run of the device, the dip stick was used to compare and confirm the accuracy of the delivered water level report by the device at the two intervals of interest, 20% level and 80% level. The device was tested for ten trials at three different days and the recorded results for the first and third trials presented in Table 2, Table 3. Onsite septic tank contains scum, a film or layer of foul or extraneous matter that forms on the surface of wastewater. In order to assess the impact of foamy wastewater on the developed device, 5 g of laundry detergent powder was used to make foamy water before pouring it inside the bucket. After ten trials with the foamy water, the obtained results was compared with that of non-foamy water and presented in Table 3. The mobile phone numbers from different telephone network operators were implemented in the enrolled GSM numbers for the comparison of the response time of the smart sewage device. The experiment was to demonstrate the effectiveness and efficiency of the developed device.

Table 2.

Response Time of the GSM Module during first day test run of the prototype smart septic tank.

Number of Trials	Mobile phone 1. Time SMS message was delivered	Failed delivery	Mobile phone 2. Time SMS message was delivered	Failed delivery
1st trial	3 s	None	2 s	None
2nd trial	2 s	None	2 s	None
3rd trial	2 s	None	2 s	None
4th trial	2 s	None	3 s	None
5th trial	3 s	None	2 s	None
6th trial	2 s	None	3 s	None
7th trial	2 s	None	3 s	None
8th trial	2 s	None	4 s	None
9th trial	3 s	None	5 s	None
10th trial	2 s	None	3 s	None
AVERAGE TIME	2.3 s		2.9 s

Table 3.

Response Time of the GSM Module during third day test run of the prototype smart septic tank with water compared to that of foamy water.

Number of Trials	Mobile phone 1. Time SMS message was delivered with water	Mobile phone 1. Time SMS message was delivered using foamy water	Failed delivery	Mobile phone 2. Time SMS message was delivered with water	Mobile phone 2. Time SMS message was delivered using foamy water	Failed delivery
1st trial	2 s	4 s	None	2 s	3 s	None
2nd trial	2 s	5 s	None	2 s	4 s	None
3rd trial	2 s	4 s	None	3 s	5 s	None
4th trial	3 s	4 s	None	2 s	3 s	None
5th trial	3 s	5 s	None	2 s	4 s	None
6th trial	3 s	4 s	None	3 s	3 s	None
7th trial	2 s	4 s	None	3 s	3 s	None
8th trial	2 s	4 s	None	4 s	4 s	None
9th trial	3 s	3 s	None	3 s	3 s	None
10th trial	2 s	3 s	None	2 s	4 s	None
AVERAGE TIME	2.4 s	4.0 s		2.6 s	3.6 s

In line with the obtained results the smart septic tank performed well delivering the report of the level of water in the bucket to the two enrolled mobile phone numbers in less than a minute. The marked water level on the dip stick matched with the delivered text message reports with less than approximately 1 cm vertical height difference attributed to the slight delay in the response time of the GSM network. It was also observed that there were some slight delays in the delivery time of the text messages during the trial with foamy water. The delay in the response time may be due to deflections of the acoustic waves by the uneven foamy water at the interface or with the telecommunication network. The total recorded delay was less than 10 s which demonstrates that the developed device can effectively function even with foamy scum in the septic tank.

4. Discussion

Existing onsite sewage tanks are monitored manually to check the level of sewage in the septic tank. The developed remote sensing device can only be applied to onsite septic tanks. The impact of the solution can be assessed considering the population of the users of onsite septic tanks. Previous reports show that there are many sewage disposal systems however the choice of one depends on the geographical location, economic status of the users, and architectural structure of the buildings, etc. [20,21] The onsite sewage septic tank system remains the dominant choice in Africa creating a ready market for the developed device.

Some of the existing sewage management technologies and their operation [22] are presented in Table 4.

Table 4.

A comparison of the cost of the available sewage level monitoring devices, their operational technologies deployed in the processing of wastewater.

S/N	Sewage level management device	Operation
1.	Smart Sewage Management Device Based on Internet of Things (IoT). Texas Instruments. Unit cost is $2,400.	It implements ESP8266 board to sense a blocked sewage drainage system and then sends notification to any enrolled municipal authority for necessary action. It requires internet for its operation making it unsuitable for remote locations of Africa where internet is unavailable, unstable and expensive.
2.	UsenSewer, an automated sewerage management system. Unit cost is $3,500.	The device uses Arduino microcontroller coupled with an ultrasonic sensor, a NRF module and GSM module to automatically monitor wastewater pipelines for blockages. It is developed for wastewater blockage detection and removal in Bangladesh. It costs about $3,500 so very expensive.
3.	30GM70 Series Ultrasonic sensor. Unit cost is $1,750.	It detects sewage sludge to prevent overfilling of septic tanks. It triggers a switching signal to stop the flow of material when maximum fill level is reached. The device is used where multiple sewage tanks are connected together to regulate and direct the flow. It is not for single onsite septic tanks.
4.	SepticSitter. Unit cost is $2,239	The device is an early warning system for onsite sewage systems. It is installed in septic, pump tanks and drain fields to prevent hazardous system overloads. The technology is complex and expensive. This device relies on internet for its operation making it unattractive for low income countries of Africa.
5.	LIDOTT Sewer level monitoring sensor. Unit cost is $5,499.	It is a data logging device for monitoring sewage systems. The device senses depth, pressure and changes in temperature in the sewage system. The data is online real-time which requires a stable internet for effective operation.

The cost of the developed device is less than two hundred dollars so it is very marketable compared to the products in the market as shown in Table 4. The available methods of sewage waste disposals are: the municipality system, off-site sewage system, onsite sewage system, full wastewater system, lagoons, and pit latrines. The onsite sewage system is very popular because of its ease of integration in buildings at locations [23,24]. The municipality system utilizes a waste plant in treating the wastewater linked directly to the plant. The off-site sewage system requires that the buildings within plots are connected to a common waste line for treatment and disposal as seen in urban locations of high income countries. Although the municipality system of sewage management and treatment is safer, it is more challenging to diagnose a fault and repair the system. It also takes a long time for repairs with so many inconveniences to the users of the facility [25]. The implementation of the developed device will make onsite septic tanks more efficient and an excellent alternative to the urban systems.

Presently, there are very few variant sewage level management technology devices that deliver early warning signals directly to septic tank evacuation agents and the facility users for the purpose of timely evacuation of the onsite septic tank to prevent overflowing. However, there exist some sewage level management devices that utilize ultrasonic sensor technology to detect blockages in sewer pipelines through open channel flow calculations and level sensing especially in high rise buildings [26]. Such technologies are deployed mostly in municipality systems and off-site sewage systems requiring a central collection plant for the treatment and disposal of sewage waste [27].

The available sewage level management devices that delivers online real time reports that includes level of sewage in septic tanks are unsuitable for low income countries of Africa due to their reliance on internet, electric power grid, and high cost. They implement complex sensor architecture in a bid to detect sewage level, pressure and temperature simultaneously thereby increasing the cost of the device making it unattractive for Sub-Saharan Africa [28].

4.1. Field test of the developed device

The developed smart sewage system was installed in an existing concrete onsite septic tank with dimensions, freeboard 0.3 m, depth 2 m, width 1.5 m, and length 3 m located at Lagos, Nigeria. The solar module was mounted on a pole 5 m long and the smart sewage device was fixed on the inspection access hole of the septic tank. The initial freeboard depth as at the start time was 30 cm. The scum level at start point was obtained by lowering a calibrated 3 m dip stick gauge vertically down the concrete septic tank and the measured length from the scum level to the surface was 30 cm. The smart sewage device was set to read 20% at 24 cmand 80% at 6 cm. The filter at the septic tank outlet was removed and the outlet covered with polythene to simulate a blockage. On the 2nd day from inception, the smart sewage system delivered a text-message to the three enrolled mobile phone numbers indicating “Attention! The Septic Tank is malfunctioning, the sewage level is rising”. The calibrated dip stick was lowered immediately which confirmed the level from scum to the surface to be 24 cm. On the 6th day from inception, the device delivered another text-message to the enrolled phone numbers indicating septic tank full. Upon confirmation of the scum level using the calibrated dip stick it was at 6 cm depth to the surface.

Although the developed device performed excellently well during this field test, there are possibilities that the delivered text messages might be slightly delayed if the scum in the onsite septic tank are very foamy as shown during the laboratory test presented in Table 3. This delay caused by the partial deflection of the acoustic waves at the foamy interface is very minimal and therefore falls within the tolerance range of the device.

4.2. The novelty in the smart sewage device

The novelty in the developed device are in the strategic approach in solving the problem of overflowing onsite sewage septic tanks through the application of relatively low cost, simple electronic components powered by a renewable clean energy. The implemented solar power enables it to decrease reliance on the power grid such that it is functional at remote areas of Africa most vulnerable to the hazards of overflowing onsite septic tanks. It does not require internet for its operation unlike the available variants. The sensor architecture which focuses on remote sensing of sewage level in septic tank alone reduced the number of deployed electronic components thereby lowering the total cost of the product and also achieving low electric power consumption. Thus the developed device is suitable, very effective and efficient for Sub-Saharan Africa where onsite sewage septic tank usage is dominant.

With the implementation of the developed remote sensing of onsite sewage tank levels, users can now detect malfunctioning septic tank early to make proper arrangements for the evacuation of the septic tanks to prevent the overflow. The pollution and contamination of the environment associated with the overflow of the sewage tank is curtailed.

4.3. The limitations of this research

The scope of this work does not cover the assessment, evaluation and sampling of the contaminants and infectious diseases associated with the overflowing onsite sewage septic tanks and the impact on the environment. The study is limited to the development of the remote smart sewage septic tank level monitoring device and how it improves the efficiency in the evacuation of the septic tanks and mitigates the problems of overflowing onsite sewage septic tanks.

The first phase of this research have developed the smart onsite sewage system which delivers early warning on malfunctioning onsite septic tanks and alerts the enrolled users on the levels of the sewage for the prompt evacuation. The next stage is the development of an innovative mobile application that will create user graphical interface for the sewage waste evacuation service agents to receive information directly from the smart sewage system and be able to know the fastest route to access the onsite septic tank needing evacuation and the volume of sewage in the septic tank. The users of the mobile application can track the sewage suction tanker trucks at any point during the evacuation cycle.

5. Conclusion

The overflowing of onsite sewage tanks is one of the major sources of contamination of the environment in most African countries. In Nigeria, about 80% of the buildings in the remote areas use onsite sewage tanks. The water supplies from the central national water boards are grossly inadequate so residents rely on water from shallow wells which are easily contaminated by seepages from overflowing sewage tanks. Consequently, diseases like cholera are easily transmitted through overflowing sewage tanks leading to epidemic of infectious diseases.

The developed smart remote sensing septic tank provides solution to the challenge of overflowing sewage septic tanks in Africa. The septic tank level to trigger alert can be determined by the user and the sewage evacuation agent. Allowing the device level settings to be user-defined enables the sewage evacuation agent to plan well and be very effective and efficient in performing their duty, ensuring that the septic tank does not overflow.

Although there were no failed SMS messages deliveries during the test run of the prototype device, there are chances that there may be failed deliveries in practice. However, since the message is transmitted to more than one phone number, any receiving party can act accordingly. The enrolled mobile phone numbers is good to be obtained from different telephone operators so that if any of the telephone networks is down, the other available mobile networks will deliver the SMS messages upon trigger by the device.

The release of seepages of sewage from overflowing onsite sewage septic tanks causing the spread of contaminants and contagious diseases will be eliminated by the implementation of the developed smart remote sensing sewage septic tank system. Also reliable data generated from the sewage septic tank levels and evacuation period will be made available to agents and researchers needing the records. The developed smart sewage septic tank is very important in hospital buildings especially in facilities for treating infectious deceases. Smart cities located below sea levels very close to the rivers are more susceptible to contaminations from overflowing onsite septic tanks and therefore are the focus of the developed device. The developed technology and its implementation in the evacuation of onsite sewage tank is a step towards the mitigation of pollution.

Author contribution statement

Uzoma Ifeanyi Oduah: Conceived and designed the experiments; Performed the experiments; Analyzed and interpreted the data; Contributed reagents, materials, analysis tools or data; Wrote the paper.

Emmanuel B. Ogunye, B.Sc.: Performed the experiments; Analyzed and interpreted the data; Contributed reagents, materials, analysis tools or data; Wrote the paper.

Funding sources

No funding.

Data availability statement

Data will be made available on request.

Declaration of interest’s statement

The authors declare no competing interests.