Physicochemical and bacteriological characterization of raw sewage from the Meknes region Morocco

. The region of Meknes suffers from a significant delay in the water sector, including sewage treatment. The Urban waste water in the region originates from various activities; households, industry, agriculture and hospital. These waters are released in to nature without any treatment, which constitutes a serious risk for the environment. The objective of this research is to characterize the physicochemical and bacteriological pollution of the three sewage collectors of the Meknes region (Aïn Choubbik, Oued Ouislane and Aïn Taoujdate). Indeed, the pollution parameters; biological and chemical oxygen demand are abnormally high, which indicates clearly that waste waters is rich of reducing or oxidizing organic materials. Ammonium, nitrogen, phosphorus and heavy metals concentrations exceed the limit values. So these waters are classified as bad or very bad quality. On the one hand, the presence of a large bacterial load indicates fecal contamination. The total coliform, fecal coliform and fecal streptococci levels are high exceeding exceed the values specified the WHO guidelines and the Moroccan standards. This situation is likely to cause serious and irreparable damage to the environment groundwater. To counter this, make the necessary investment in sewage treatment and other remedial measures is key to preventing pollution and its spread.


Introduction
In Morocco, water scarcity, waste and pollution are increasingly becoming a concern. Indeed, population growth and droughts since the 1970s are affecting water availability. The gap between the needs and availability of water increase might increase the size with the increasing of water-consuming sectors of all water-consuming sectors of the country. In order to address this situation, promoting the re-use of treated wastewater in agriculture becomes essential. It's is a very useful and very ancient practice across the globe [1]. At present, there is an area of about 7000 hectares directly irrigated with raw wastewater discharged by towns (about 70 million m 3 / year) with no precautionary measures. Meknes Region is the largest surface of wastewater irrigated crops. It is estimated about 1400 ha. It generally corresponds to it is of the order of 1400 ha and it concerns the cereals, the market gardens and the arboriculture [2]. The waste water reuse in agriculture constitutes a potential risk to human health and the environment. This study aims to evaluate the physicochemical and bacteriological parameters of the three sewage collectors of the Meknes region (Aïn Choubbik, Oued Ouislane and Aïn Taoujdate).This is intended to demonstrate the need for the treatment of waste water before being used in agriculture.

Fig1. Map of sampling points
The choice of sampling sites is based on their environmental features and on their use in agriculture.

S2
The selected sites are; Site (S1): Oued Ouislane belongs to the superficial hydrographic network of the region of Meknes, originates at the south-east of the village of Boufekrane. The sewage of Oued Ouislane is reused by the farmers. Site (S2): Aïn Taoujdate is known for its agricultural and industrial activities (30 Km from Meknes). The residual urban water includes the flow from the households, industry, and discharges from the municipal slaughterhouse. This wastewater is reused for agriculture. Site (S3): Aïn Choubbiik is the sanitation network, it receives the effluent from the Mohamed V hospital without treatment, and this wastewater will be directed towards Oued Bourouh located downstream. This water is reused in agriculture and for livestock watering. Sampling is done in the morning between 10am and 1pm (time of rejects) in the summer 2017. Glass vials with screw caps are used and they are sterilized beforehand in the laboratory according to the protocol mentioned in Table 1. Few drops of sodium thiosulphate are added to vials for bacteriological analysis sampling, they are added in the vials before sterilization to destroy the chlorine which may exert its action on the bacteria during transport. Some physico-chemical parameters as temperature and pH are measured in situ.

Physicochemical characterization of analyzed waters
The results of physicochemical characterization of raw sewage in the region of Meknes are summarized in Table 4. Table4. Results of physicochemical characterization of raw waste water from the studied sites during the period of April-August 2017.

Température
The average temperature of raw sewage in the region of Meknes is between 19.43 -21 ° C. The temperatures recorded are included in the range of the direct discharge limit values in the receiving environment [5] and in the range of Moroccan standards for water quality for irrigation [6].

3.1.2.pH
The pH values of the raw sewage show that these waters are slightly alkaline and fall within the range of Moroccan standards for water quality for irrigation [6] and within the range of direct discharge limits [5]. The values of the conductivity recorded at the level of the raw wastewater of the different sites vary between 1745-1895μs / cm. This reflects an important mineralization (waters rich in salts and minerals). Electrical conductivity indicates the degree of overall mineralization; it provides information on the level of salinity. The electrical conductivity values meet the international regulatory standards for direct discharges and for irrigation of the crops [5,6].

The chemical oxygen demand COD
Chemical Oxygen Demand is an important water quality parameter because, it provides an index to assess the effect discharged wastewater will have on the receiving environment.
Higher COD levels mean a greater amount of oxidizable organic material in the sample, which will reduce dissolved oxygen (DO) levels [7].The average values recorded in the sites are very high (Table 4) and exceed the limit values of direct discharges [5], therefore, these waters are of very poor quality.

Biological oxygen demand DBO5
The BOD (Biochemical Oxygen Demand) is a measurement that aims to give the amount of organic material that can be broken down by micro-organisms. It is a widely-used parameter, which can be applied to all water types, especially sewage and purification processes [7].The average BOD5 concentrations of the three study sites ranges from 425 mg O 2 / L, 700 mg O 2 / L in urban waters of Ain Shubbiik and Ain Taoujdate respectively, these values are greater than limit values for direct discharges (100 mg O 2 / l) [5], therefore, these waters are of very poor quality.

Ratio DCO/DBO5
The COD / BOD5 ratio provides a deduction of the origin of wastewater pollution. In fact, a low value of the COD / BOD5 ratio indicates the presence of a large proportion of biodegradable materials and a biological treatment is envisaged. Inversely, a high value of this ratio indicates that a large part of the organic matter is not biodegradable therefore, physicochemical treatment is envisaged.
The average values of the ratio COD / BOD5 are 1.9, 2.18, and 2.28 in the waters of Oued ouislane, Ain Taoujdate and Aïn choubiik respectively. Therefore, it can be concluded that the wastewater in our study is easily biodegradable In spite of its high organic load. In addition, the values of the ratios are significantly lower than 2.5. On this basis, it can be concluded the dominance of domestic-type effluents [8].

Orthophosphate
The concentrations of orthophostate in the studied waste water are 20.5, 32.5 and 35.1 mgP /l for Oued Ouislane, Ain Taoujdate and Aïn choubiik respectively. These high values could be explained by wastewater discharges [8,9].

Nitrogen
The concentrations of ammonium are high at different sites. A high level of nitrogen in the ammonium form is not toxic, but in alkaline waters (pH greater than 7.5), as was the case in our water analysis, a fraction could be transformed into ammonia form (ammonia gas) which is toxic.

Sulphate
Sulphate concentrations meet the limits values of direct discharges of wastewater and the ones of crop irrigation [5,6].  Results of the Oued Ouislane have been compared over the years [11] and allowed to conclude that the bacteriological quality has been deteriorating over the years. On, makes it possible to conclude that of the water has deteriorated over the years. The magnitude of fecal bacterial contamination of rivers, especially during the summer months, may be an imminent health risk [11].

Bacteriological analyses
The average value of the fecal streptococci (SF) are 1, 710 8 ; 510 6 ; and 1, 210 3 of Ain taoudjdate, Aïn Choubbik, Ouislane respectively. Aïn choubbik site receives hospital Mohamed V effluents, which explains that Pseudomonas aeruginosa, were found only in this site. These waters are used without treatment in the irrigation, which constitutes health risk for major consumers. The pathogenic germs such as genus Salmonella have been systematically sought for the three sites. None of the sites contained Salmonella bacteria. These results are consistent with previous study done on oued Ouislane [1,12].

Conclusion
The physicochemical analysis of wastewater in the Meknes region has showed that these waters have a COD / BOD5 ratio less than 2.5, which indicates clearly that they are biodegradable. On the other hand, the analysis reveals the presence of heavy metals. However, microbiological analysis revealed very high concentrations of germs in these waters, which constitutes a health risk. To address this issue, Wastewaters must, before being discharged into a natural receiving body, be treated. (The wastewater collected must flows through a number of preliminary treatment installations) (Case of Oued Ouislane and Mohamed V Hospital effluents).
To sum up, the studied wastewater should not be reused directly in agriculture or other activities as is no the case To protect health or environmental quality, adequate treatment of wastewater discharges must be considered before any use. The quality of treated wastewater released must meet established standards.