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Physico-Chemical and Bacteriological Characterisation of Domestic Wastewater from Adétikopé in Togo

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29 July 2023

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31 July 2023

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Abstract
Background: Wastewater represents a health risk for populations. For sanitary safety, it is important to know their physico-chemical and microbiological qualities in order to better understand the risks incurred by the population. Objective: The aim of this study is to analyse the microbiological and physico-chemical quality of domestic wastewater in Adétikopé. Methodology: 12 wastewater samples were collected in Adétikopé from December 2022 to February 2023. Physico-chemical parameters were determined in accordance with AFNOR T90-105/ T90-023 and French standard NF T 90101. In microbiology, AFNOR was used as a reference for the detection of germs contaminating wastewater. Results were assessed in relation to European Union Criteria 98/83/EC. Results: The wastewater analyzed had a pH close to neutral, with an average pH of 7.05. The pollutant load generated ranged from 32 mg/l to 201 mg/l for BOD5, from 660 mg/l to 900 mg/l for COD and from 408 mg/l to 2080 mg/l for suspended solids. Concentrations of fecal coliforms and fecal streptococci are very high, far exceeding WHO guidelines for population health safety.
Keywords: 
Subject: Public Health and Healthcare  -   Public, Environmental and Occupational Health

1. Introduction

Water, which is present in large quantities on Earth and is essential to the survival of every living thing, animal or plant, is not just an ordinary liquid; it has original physical properties that result from the composition of its molecules and the way in which these molecules bind together. It can be found in three forms: liquid, solid or gaseous [1]. It must be classified as a universal heritage and therefore protected, defended and treated as such. It is a vital resource for mankind; it is also vital for our agricultural and economic activities, and the quality of our environment is closely dependent on it [2]. However, it is a universal receptacle for all types of pollution [3]. Although apparently inexhaustible, water is very unevenly distributed across the planet. In the short or long term, all countries will have to face up to the problem of water scarcity, as the mobilization of surface water has always been a major concern for public authorities [4].
This exacerbated use of water is due in part to the steady growth of the population, and changes in production and consumption patterns are leading to an ever-increasing production of wastewater of many different kinds, most of which is discharged directly into the environment, without any proper treatment. The various ways in which this waste is managed contribute to the discharge of potentially dangerous substances into the environment, raising many questions about their risk to human health. [5,6]. Waste management is a major problem throughout the world. It poses both an environmental and a public health problem. These issues are becoming increasingly important in the various debates on sustainable development, and are a major concern for both developed and developing countries. As a result, the environment is at the heart of a number of international meetings [7].
In Western countries, the question is posed in terms of the effectiveness of existing waste disposal methods, whereas in Africa, few countries are really interested in existing management methods [8]. Urban waste management is therefore one of the most worrying environmental issues for developing countries [9,10,11]. People's lack of knowledge or awareness of the issue, inadequate funding and institutional frameworks, and a lack of infrastructure, equipment and reliable data all contribute to exacerbating the difficulties encountered in managing the urban ecosystem in general and urban waste in particular [12,13].
Togo, a West African country with an estimated population of 7.6 million in 2020, is also facing this challenge [6]. When it comes to sanitation and hygiene, households do not use a healthy method of disposal. More than 06 out of 10 households (67.5%) discharge wastewater directly into the environment, including 25.1% into the street. In Lomé, the capital, 52.5% of households evacuate wastewater into the street compared with 53.0% in urban areas generally [8]. Adétikopé, the capital of the commune of Agoè-6, with its fast-growing population, is not spared from this scourge [14,15]. Indeed, the population increase and gradual urbanisation of this locality have obviously been accompanied by the massive production of household wastewater, resulting in the uncontrolled dumping of wastewater in the streets and close to homes. This is compounded by open defecation, particularly around the main market, and the dumping of septic tank effluent on wasteland, a situation that becomes crucial during the rainy season.
With a view to implementing a waste management strategy in the various municipalities, given the decentralisation process underway in the country, it is essential to have data on the health risks incurred by local populations. This is the background to the present study, which aims to contribute to sustainable local governance by providing data on the physico-chemical and microbiological composition of raw wastewater in Adétikopé. To do this, the aim of this study is to examine the main physicochemical and microbiological parameters of domestic wastewater in the Adétikopé locality, capital of commune 6 in the Agoè Nyivé prefecture in Togo.

2. Materials and Methods

2.1. Study Framework

2.1.1. Geographical Study

Adétikopé (Adéti-Kopé) is the administrative centre of Commune 6 in the Agoènyvé Prefecture in the Greater Lomé Autonomous District in the Maritime Region of Togo, a country in West Africa with the region code (Africa/Middle East TO18). The geographical coordinates are 6°19'23" N and 1°12'57" E in DMS (degrees, minutes, seconds) or 6.32306 and 1.21583 (in decimal degrees). The choice of Adétikopé is not accidental, given the degradation of the environment in this district, which is having a negative impact on the health situation. Added to this is the fact that Adétikopé reflects the image of a continuous peri-urban commune of the city of Lomé in the midst of an urbanisation revolution (PEUL project).
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Figure 1. Geographical location of the commune of Agoè-Nyivé 6 ( Source [16]).
Figure 1. Geographical location of the commune of Agoè-Nyivé 6 ( Source [16]).
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2.1.2. Scientific Study Framework

The study project was carried out at the Regional Center of Excellence on Sustainable Cities (CERViDA-DOUNEDON). The household survey was carried out with the support of the Center for Educational, Societal, Political and Developmental Expertise of the African Institute for Biomedical, Agrifood, Societal and Environmental Sciences (IASBASE). The samples taken were packaged at the IASBASE BioPhyto-Pharma Laboratory. Analyzes were carried out at the Microbiology and Food Quality Control Laboratory (LAMICODA) and physicochemical analyzes were performed at the Water Chemistry Laboratory at the University of Lomé.

2.2. Study Material

The material consists of waste water samples taken in the Adétikopé locality from December 2022 to February 2023. After inspection of the 24 samples, twelve (12) samples (EU1 to EU12) were selected (Figures 2 and 3).
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Figure 2. Wastewater sampling in Adétikopé (Photo Terrain, CEESPOD, December 2022).
Figure 2. Wastewater sampling in Adétikopé (Photo Terrain, CEESPOD, December 2022).
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Figure 3. Wastewater treatment at the Laboratory (Photo Laboratory, CEESPOD, January 2023).
Figure 3. Wastewater treatment at the Laboratory (Photo Laboratory, CEESPOD, January 2023).
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2.3. Analytical Methods

2.3.1. Analysis Methods for Physicochemical Parameters

The analyses focused on the following main parameters likely to characterise these waters [17]
In situ parameters: pH, temperature and electrical conductivity are determined using a multiparameter analyser of the Eutech instrument type.
Measurement of chemical oxygen demand: The principle of COD measurement involves boiling a sample in an acid medium under reflux for 2 hours, in the presence of a quantity of potassium dichromate (oxidising agent), silver sulphate (acting as an oxidation catalyst) and mercury sulphate II (allowing chloride ions to be complexed). The excess potassium dichromate is then measured. The method used is that of the French standard (NF T 90101).
Measurement of biological oxygen demand: The principle of measuring BOD5 consists in determining the quantity of oxygen consumed after five days of incubation, under test conditions, at 20°C in a dilute solution of the sample. To determine BOD5 , two measurements of dissolved oxygen must be taken: (1) at time t=0, at the time of incubation and (2) at time t=5days, after 5 days. BOD5 is determined by the respiratory method using an INOLAB BOD meter in accordance with the technique described in NFT 90-103.
Measurement of suspended solids: Suspended solids are determined by filtering a volume of wastewater through a cellulose filter (0.45 μm) using the NFT 90-105 method.
Determination of total phosphorus: The concentration of orthophosphates is determined by the colorimetric method by forming a complex with ammonium molybdate and potassium antimony tartrate in an acid medium, in accordance with ISO 6878.
Measurement of dissolved solids, oils and fats: Dissolved solids were determined using a salinometer. Oils and fats were determined by drying at 105°C.

2.3.2. Methods for Analysing Microbiological Parameters

Microbiological analyses of wastewater initially focused on the enumeration of thermotholerant coliforms (TC), faecal streptococci (FS), sulphite-reducing anaerobes (SRSA) [18]. Secondly, pathogenic bacteria were isolated, purified and identified.
Enumeration: Microbiological analysis of the samples was carried out as soon as they were received in the laboratory, in order to avoid any possible change in the initial microbial concentration. A series of dilutions were made in sterile distilled water. Only the 10-2 and 10-3 dilutions were used to count the faecal contamination indicators (CT and SF).
Enumeration of faecal contamination indicators: The search for and enumeration of TCs and SFs were carried out using the liquid enumeration method by determining the most probable number (MPN). The enumeration results were determined using the Mac Grady table (Rodier, 2009).
Detection and enumeration of thermotolerant coliforms : Colimetry consists of detecting and enumerating coliform germs, including TCs. It is carried out in two stages: (1) Presumptive detection of coliforms on Bromocresol Purple Lactose Broth (BCPL) medium. (2) Confirmatory testing for TC on Schubert medium [19].
Enumeration of faecal streptococci: FS are enumerated in liquid medium using two culture broths (Rothe medium and Eva-Litsky medium). This method uses two consecutive tests: a presumptive test followed by a confirmatory test [19].
Enumeration of anaerobic sulphite-reducing bacteria : ASR are Gram-positive bacteria that develop over 24 to 48 hours on liver agar (VF), producing typical colonies that reduce the sodium sulphite (Na2 SO3) present in the medium to sulphide, which in the presence of Fe2+ produces black FeS (iron sulphide). The spores of RSAs are generally indicators of past contamination [3].
Isolation of Salmonella Spp: The agars used are : Hektoen, Salmonella-Schigella (SS). Streak plating on Petri dishes is most often used for isolation purposes. The inoculum is taken directly from the water to be analysed, deposited on a peripheral point of the agar and then streaked over the entire surface. The plates are coded and then incubated at 37°C for 24-48 hours [20].
Purification: Once isolated, the strains are purified by successive subculturing onto the appropriate isolation medium [20].
Identification: Isolated and purified bacterial colonies are seeded on selective culture media (Hektoen, SS,). Identification is then carried out using the Api 20 E plate system (Biomérieux, France). It is based on the assimilation of 12 carbon sources and the use of 8 biochemical tests by Gram-negative enteric and non-enteric bacteria. Identification is carried out using API WEB [20].

2.3.3. Processing Statistical Analysis of Data

Using Excel 2016 (MicroSolft Office 365), the data collected was entered and formatted in accordance with EPI info version 6.04 fr of April 2001 developed by CDC Atlanta, a software package used to carry out all the processing and analysis. The values obtained were compared using the significance level p. Values of p < 0.05 are considered significant and values of p < 0.01 are considered highly significant. Values are expressed as mean value ± standard deviation. The axes of these statistical treatments were the descriptive statistics of the socio-demographic parameters (ethnic group, level of education, age and sex), the hierarchical classification based on multivariate component analysis (Analysis of physico-chemical and microbiological analysis categories) and the descriptive statistics of the groups obtained (Me: mean, CV: coefficient of variation), respectively, to test and describe the variation in the values obtained.
The following assumptions were made: (1) Assumption H0 : no significant variation between the percentages compared; (2) Assumption H1 : there is a significant variation between the percentages compared.
The value of the probability p' is given by the Epi info6 software. The decision and conclusion are as follows: (1) If p' < p: acceptance of H1 ; The conclusion is that there is a significant variation between the percentages of the values compared. The value may have a significant increase or decrease in relation to the target value; (2) If p' > p: rejection of H1 ; It is concluded that there is not a significant variation between the percentages of the values compared.
The percentages are compared sample by sample and between sampling sites. Epi info6 does not give the probability value α' when the percentage of modalities is obtained from a small number of samples (n=5).

2.4. Ethical Considerations

The survey authorisations were issued by the authorities of the Regional Centre of Excellence on Sustainable Cities in Africa (CERViDA-Dounedon) (CERViDA-Dounedon) of the University of Lomé and the Town Hall of Commune Agoè 6, which helped to reassure the households. The household survey was administered with the consent of the respondent. Measures were taken to guarantee the confidentiality of the identity of the households to be surveyed. In addition, the survey was conducted with strict respect for the population and its cultural values, with a translation of the questionnaire into the local language for those who had difficulty with French.

3. Results

3.1. Physicochemical Parameters

Before wastewater is discharged into the natural environment, it must comply with standards established to protect the receiving environment from all types of pollution. The results of the physicochemical parameters of the wastewater sampled are presented in Table 1.
Table 1. Physicochemical properties of the wastewater sampled.
Table 1. Physicochemical properties of the wastewater sampled.
Physico-Chemical parameters EU1
 EU2 EU3 EU5
 EU6 EU9 EU4
 EU7 EU8 EU10
 EU11 EU12 P Values
Temperature (T) °C 30,1 30,4 31,0 30,9
 31,4 30,8 30,3 30,2 31,2 31,2 31,8* 31 P<0,05
pH 7,22* 7,18 7,01 6,96 6,87 7,03 7,20 7,20 6,99 6,99 6,91 7,05 P<0,05
Cond elec 20°C - µs/cm 2180 4180 3660 2270 2300 6390 2160 4200 3640 2300 2340 6410* P<0,001
Dissolved solids - mg/L 1559 2989 2617 1623 1645 4569 1539 3009 2597 1653 1685 4589* P<0,001
Suspended solids (SS) -mg/L 410,0 542,9 2080* 600 590 900 408 544,9 2078 630 630 920 P<0,001
D. Oxygen Chemistry (COD) - mgO /L2 800 820 660 780 860 - 820 800 680 810 900* - P<0,05
D. Oxygen biol. (BOD5 ) - mgO /L2 75,0 40 65 40,0 201 30,0 55,0 60 45 43,0 205* 32,0 P<0,001
Total phosphorus (Pt) - (mgP/L) 10,2 22,4* 17,9 11,7 5,9 4,5 10,4 22,2 18,1 12,0 6,3 4,7 P<0,001
Kjeldahl nitrogen (NTK) – mgN/L - - - - - - - - - - - - -
Oils & Greases (HG) -mg/L 14,8 < 5,0 12,0 <5,0 20,0 59,0 14,6 5,2 11,8 5,3 20,4 61,0* P<0,001
* Anova comparison model value.
Temperature: During this study, temperature values varied between 30.1°C and 31.8°C. The highest temperature values were recorded for sample EU11, while the lowest value was detected for sample EU1. The average temperature values detected during our study were below 35°C, considered to be an indicative limit value for water intended for crop irrigation.
pH: The pH values of the water samples taken were neutral and varied between 6.87 and 7.20. Acidic values were obtained for EU 5, 6, 8, 10 and 11; neutral values were obtained for EU 3, 9 and 12; basic values were obtained for EU 1, 2, 4 and 7.
Conductivity: Generally speaking, the conductivity values detected vary between 2160 µs/cm and 6390 µs/cm.
Chemical oxygen demand: The highest COD concentrations were recorded at EU11, with a value of 900 mg/l. This is still within the standard set at 120 mg/l, which is considered to be the limit value for direct discharge from wastewater treatment plants.
Biological oxygen demand: The maximum BOD concentrations detected at5 were 205 mg/l.
Suspended matter: The results obtained show that the raw wastewater is characterised by fairly high concentrations of suspended matter: 1053.5 mg/l. The TSS levels recorded in the wastewater do not comply with FAO standards, which are set at a maximum of 30 mg/l.
Total phosphorus: The highest concentration detected was 22.4 mg/l.
Dissolved solids, oils and greases: The average concentration of dissolved solids was 2506.17 mg/l, with extreme values of 1539 and 4589 mg/l. The oil and grease content of wastewater from the Adétikopé locality varies from values < 5 to 61 mg/l. .

3.2. Bacteriological Parameters

Enumeration : The enumeration results obtained during our study period show that the CT, CF and SF concentrations recorded in the water samples are very high and vary respectively between the plant inlet, the clarifier outlet and the plant outlet.
Search for and enumeration of thermotolerant coliforms : Figure 4 shows the results of TC enumeration. The highest levels of these germs were detected in the samples taken at Dévimé and Tnoukoutsi, with values of between 68,000 CFU/100ml and 65,000 CFU/100ml respectively. The lowest values were obtained in the wastewater from Adétikopé centre and Kladjémé, with values of < 1 CFU/100ml. The high concentrations detected at Dévimé and Tonoukoutsi show that the raw water is highly contaminated with human and animal faecal matter.
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Figure 4. Results of the TC count.
Figure 4. Results of the TC count.
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Research and enumeration of faecal streptococci: Figure 5 shows the results of the SF enumeration of the wastewater sampled. The maximum values of these germs detected were 47,000 CFU/100 ml and 45,000 CFU/100 ml in Loményokopé and Tsikplonou respectively. The lowest concentrations were recorded in the wastewater from Adzové and Agnavé.
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Figure 5. Results of the FS count.
Figure 5. Results of the FS count.
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Determining the origin of faecal contamination: The origin of faecal contamination is determined by the quantitative ratio R= CT/SF. According to the criteria defined by Borrego and Romero in 1982, contamination is of animal origin if the R ratio is less than 0.7, and of human origin if R is greater than 4. The origin of the contamination is predominantly animal if R is between 0.7 and 1, uncertain if R is between 1 and 2, and predominantly human if R is between 2 and 4 [3]. The values obtained for the TC/SF ratios are presented in Table 2. The results obtained showed that the origin of faecal contamination is both animal and human.
Table 2. Minimum, average and maximum values for physico-chemical parameters of wastewater sampled.
Table 2. Minimum, average and maximum values for physico-chemical parameters of wastewater sampled.
Adétikopé
Parameters Minimum Average Maximum p Values
Temperature (°C) 30,1 30,86 ± 0, 52 31,8 P<0,05
pH 6,87 7,05 ± 0,12 7,20 P<0,05
Conductivity (µS/cm) 2160 3502,5 ± 1569,43 6410 P<0,001
BOD5 (mg/l) 40 74,25 ± 61,60 205 P<0,001
COD (mg/l) 660 793 ± 73,34 900 P<0,001
TSS (mg/l) 408 1053,5 ± 590 ;07 2080 P<0,05
PT (mg/l) 4,5 5,43 ± 6,53 12,87 P<0,001
Dissolved solids (mg/l) 1559 2506,17 ± 1122,35 4589 P<0,001
Kjeldahl nitrogen (NTK) – mgN/L - - - -
Oils & Greases (HG) -mg/L <5 22,41 ± 20,46 61,0 P<0,001
* Anova comparison model value.
Table 3. Origin of faecal contamination in raw wastewater samples.
Table 3. Origin of faecal contamination in raw wastewater samples.
Period CT/SF Origin of the Contamination
Wastewater from Tsikplonou [EU1] 0,2 Animal origin
Kpotavé wastewater [EU2] 61,90 Human origin
Tnoukoutsi wastewater [EU3] 46,43 Human origin
Agotimé wastewater [EU4] 0,08 Animal origin
Kladjémé wastewater [EU5] <0,7 Animal origin
Wastewater from Dzové [EU6] 1,94 Origin uncertain
Wastewater from Lomenyo Kopé [EU7] 0,08 Animal origin
Wastewater from kpokplomé [EU8] [FR >4 Human origin
Dévimé wastewater [EU9] 35,79 Human origin
Adoglové wastewater [EU10] 0,08 Animal origin
Wastewater from Adétikopé Centre [EU11] - Origin uncertain
Wastewater from Agnavé [EU12] >4 Human origin
Research and enumeration of sulphite-reducing anaerobes: The maximum values of these germs detected in waste water are very low, whatever the type of sample .
Research and enumeration of Salmonella Spp:Salmonella Spp was not detected in the wastewater analysed.

4. Discussion

The results of microbiological and physico-chemical analyses of wastewater from the commune of Adétikopé show a diversity of parameters that has been commented on in previous studies of wastewater. The average values obtained show significant differences between them (P<0.05). With regard to physico-chemistry, temperature is an important abiotic factor. Its measurement is necessary, given the role it plays in the solubility of gases, the dissociation of dissolved salts and the determination of pH [21]. Increasing this parameter promotes self-purification and increases the rate of sedimentation, which is of interest in wastewater treatment plants. In addition, temperature accelerates chemical and biochemical reactions [22]. Although the temperature values are below the proliferation limit for microorganisms, there is a significant difference between the waters analysed, depending on the location (P<0.05). pH influences most chemical and biological mechanisms in water. This parameter is an important element in the interpretation of corrosion in the pipes of wastewater treatment plants [3]. The results showing an average neutral pH (P<0.05) are in agreement with those obtained by other authors [23,24]. These values are also close to the quality standards for irrigation water [25]. The electrical conductivity value is probably one of the simplest and most important for monitoring wastewater quality. It reflects the degree of overall mineralisation and provides information on the salinity level [3]. These results show a high level of mineralisation, mainly due to the organic load [26]. Comparison of the electrical conductivity values of the wastewater analysed with the quality standards for water intended for irrigation leads to the conclusion that this wastewater is not acceptable for irrigation purposes [25]. COD corresponds to the quantity of oxygen consumed chemically to oxidise all the oxidisable matter present in the water. COD is particularly suitable for measuring the pollution of industrial effluent [26,27,28]. BOD expresses the quantity of oxygen required for the destruction or degradation of organic matter in water by microorganisms in the environment. This parameter is a good indicator of the biodegradable organic matter content of water during self-purification processes [29]. The COD/BOD ratio5 reflects the fraction of easily biodegradable matter among all the oxidisable matter. The study shows a COD/BOD biodegradability ratio5 for raw wastewater of 10.68, which is greater than 2.5. This result leads to the conclusion that the effluent studied, even though it is domestic, is not predominantly domestic, which could be explained by the presence of numerous industries that pollute surface water. In addition, the value of the TSS/DBO ratio5 obtained is high compared with the usual ratio, which is between 1.2 and 1.5. These high values could be explained by the fact that suspended solids do not sediment quickly upstream of the discharge points, thus causing an increase in their content in the effluent; this increase is all the greater as the discharge flow rate is high. However, maintaining a high concentration of organic matter in wastewater considerably hampers the effectiveness of treatments designed to eliminate pathogens. While the quality standards for wastewater intended for irrigation set a limit value for suspended solids, the same is not true for BOD5 and COD, for which no limit value is mentioned [30,31,32]. The results obtained from the wastewater ratio (P<0.05) indicate that this water is poorly biodegradable, as reported in certain studies [33]. TSS represents all the mineral and organic particles contained in wastewater [34,35]. The abundance of TSS in water favours a reduction in luminosity and lowers biological production, due in particular to a drop in dissolved oxygen following a reduction in photosynthesis. Most organic phosphorus comes from detergents, protein metabolism waste and its elimination in the form of phosphates in human urine [34,35]. The increase in total phosphorus concentration is due to the extensive mineralisation of organic matter. Conductivity values indicate poor quality water, which should be treated with caution. The results obtained following analysis of the physico-chemical and bacteriological parameters of wastewater from the Adétikopé locality show two groups of parameters according to their statistical significance. Concentrations of the various parameters investigated varied from one locality to another, but were generally higher than the guide value recommended by international standards, but lower than those found in some similar studies [19,24,36]. With average pH values obtained that are close to neutral and acceptable for irrigation, the results of this study are comparable with those reported in other studies on physico-chemical and bacteriological studies of raw wastewater from cities undergoing change in Morocco [37,38,39,40,41,42]. Examination of the results also shows that the pollution parameters in the wastewater of the Adétikopé locality have values comparable to those of cities undergoing demographic change in Africa [23,24,35]. Given the concentration of raw wastewater, its direct discharge into the environment could lead to physico-chemical and biological clogging of the soil, essentially due to the presence of suspended solids, the precipitation of salts and the growth of algae on the surface of the irrigated soil. As a result, the wastewater studied, given its physico-chemical and bacteriological load, should not be reused directly. Treatment prior to any irrigation should be considered in order to improve its quality to the required standards and meet the expectations of consumers and public authorities in terms of environmental and human health protection. With this in mind, an optional lagooning process or, where appropriate, a high-yield lagooning process could be an alternative to reusing this water in its raw state.
From a microbiological point of view, the results of the faecal contamination germ count are not in good agreement with bibliographical data on the state of bacterial contamination of urban effluents [28,43,44]. The results far exceed the standard set by the World Health Organisation at 1000 TC/100 ml [43,45,46,47]. There were significant differences in the levels of micro-organisms detected in the samples (P<0.05). TCs are used as indicators of the microbial quality of water and can be indirectly associated with pollution of faecal origin [48,49,50]. The decrease observed at the Adétikopé Centre and Kladjémé sites is thought to be due to a combination of certain conditions that are unfavourable to them and that are more pronounced in summer: (1) The temperature of the environment has a direct effect on the survival of microorganisms because the rate of elimination of bacteria increases with temperature due to an increase in their metabolic activity [51]. (2) UV radiation can have a direct effect on the elimination of indicator germs through its photochemical action, inducing damage to the genetic material of cells and thus preventing their reproduction [52]. The levels of TC obtained in wastewater exceed the concentration limit (1000germs/100 ml) recommended by the WHO for the reuse of this water in irrigation [53]. Streptococci are likely to contaminate water supplies, and are typical of animal faeces. They can sometimes be present in humans or in plants [54]. The high concentrations of streptococci recorded at Loményokopé and Tsikplonou reflect the resistance of these germs in the aquatic environment containing final waste. The decrease in these germs detected at Adzové and Agnavé is thought to be due to the purification system [3]. The presence of ASR indicates the presence of iron sulphite, which causes bad odours and can be the cause of pipe corrosion [28]. These germs are often considered to be indicators of faecal pollution. The spore form, which is much more resistant than the vegetative forms of faecal coliforms and faecal streptococci, can be used to detect old or intermittent faecal pollution. The search for pathogenic germs is often justified by the presence of very high numbers of total germs. Salmonella can be altered in the aqueous environment by heat, and detection in water would require pre-enrichment (ISO 19250). However, it should be noted that pH values below 5 or above 8.5 affect the growth and survival of micro-organisms [55]. As far as microbiological parameters are concerned, it is important to consider taking appropriate measures to avoid large-scale contamination in the event of drainage by river water, which could affect human health or the evolution of flora. [56,57]. In view of the results and the observation of daily household life, and taking into account the technological prowess, education in this area is needed at the household level in Adétikopé with a view to improving wastewater management practices [58]. One essential point that must be taken into account in this education is its suitability for the population's level of education [59].

5. Conclusions

Adétikopé is an urban center where strong demographic growth, massive urbanization and the development of industrial and household activities have generated a large amount of wastewater, which can be a source of disease for the people of the Agoè-Nyivé 6 commune. Treated and raw wastewater and sewage sludge are at the origin of various sources of environmental pollution, particularly in developing countries that are less concerned about and less aware of the concomitant health risks. The aim of this study is to assess the physicochemical and bacteriological composition of wastewater discharged by households in Adétikopé. The results of the physico-chemical parameters showed that the wastewater samples were polluted by numerous organic and inorganic micropollutants. Evaluation of the physico-chemical parameters relating to wastewater from the Adétikopé locality revealed a range of information. The presence of suspended solids in effluent in quantities exceeding the standard recommended by the WHO (30 mg/l) can lead to soil clogging, with harmful consequences for crops. On the other hand, the presence of organic matter in wastewater contributes to soil fertility. Considering the concentrations of the various physico-chemical parameters of wastewater in commune 6 of the Agoè-Nyivé prefecture, the results of the physico-chemical study show that the Adétikopé locality has a high pollution load for most of the study period. The microbiological results show that the raw wastewater from Adétikopé is highly contaminated with bacteria and is not recommended for irrigation. The diagnosis of wastewater quality shows that domestic effluent is the main source of pollution. The parameters of nitrogen, phosphorus, particulate and bacteriological pollution in the water are fairly high, exceeding the admissible levels set by the FAO and WHO. Good use of water and good management of waste water means that diseases can be properly treated.

Author Contributions

Conceptualisation, GBEH; Methodology, GBEH, K K, PA ; Software, GBEH, D K A; Validation, PA; Formal analysis, GBEH, SP, KK; Survey, GBEH, AA; Resources, TT, YA; Data curation, GBEH; Original drafting, GBEH; Revision and editing, GBEH, PA; Visualisation, K Z H, K Z-K; Supervision, PA. All authors have read and accepted the published version of the manuscript.

Funding

This research was funded by the Regional Centre of Excellence on Sustainable Cities in Africa (CERViDA_DOUNEDON), the Association of African Universities (AAU) and the World Bank.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data will be made available on request.

Acknowledgments

We would like to thank the Regional Centre of Excellence on Sustainable Cities of Africa (CERViDA_DOUNEDON), the Association of African Universities (AAU) and the World Bank for providing the necessary funding that facilitated our research work leading to these results. We would also like to express our gratitude to Cyprien AHOLOU, and Kossiwa ZINSOU-KLASSOU, for their support and enlightened leadership in promoting this Centre of Excellence.

Conflicts of Interest

The authors declare no conflict of interest.

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