The Biodiversity of Algae and Physio-Chemical Parameters of the Sewage Treatment Plant and its Canal Length, Located in Sana’a City, Yemen

Abstract

This study of the biodiversity of algae is the first interest in Yemen as a future vision for sustainable alternative solutions using sustainable resources as a sewage treatment plant with its channel length in Sana’a city, Yemen. The study aimed to screen the family of algal genera. A total of 13 samples were selected with GPS, and 100 ml of water was filled up in a plastic container and directly read as wet preparation under light microscope, identified in accordance with algae standard methods in three replicates with determination of temperature, pH, and total dissolved salts. The results showed that microalgae were conducted higher than others’ algae under the mean value of temperature 28˚C and neutral pH and high total dissolved salt, indicating the economical role of algae presence and waste treating by algae in despite of there was no physical or chemical processing treatment done, and the microalgae genus was found as Chlorella vulgaries with a ratio of 100%, followed by Chlamedomonas reinhardtii and Kirchneriella lunaries with a ratio of 76.72%, and the less found genus of filamentous algae was Nostoc sp., Oscillatoria phucus, Ulotrix micrasterias, Dingoflagellate ceratium, and Desmedium with a ratio of 7.69% for each, and finally, diatoms were found along the stages. The variant of the algal family will be used soon for many applications next studies.

1. Introduction

The algal geographical distribution is a strong indicator of large differences in the degree of their endemism and species richness in diverse regions. Information is scarce for microalgae around the world, but for some groups, some genera of algae are more endemic than others in regions of low diversity [1, 2].

Algae are a group of photosynthetic autotrophs that exist in a variety of different environments, such as lakes, rivers, seas, and sewage. They produce atmospheric oxygen through photosynthesis, which is the process of converting water and carbon dioxide into carbohydrates using solar energy in nature [3, 4]. The numerous, diverse, and high-value bioactive compounds derived from microalgae make them an important, promising, and sustainable source of beneficial bioproducts [5, 6, 7].

Microalgae contain many bioactive compounds that can be extracted and produced from their cells, including lipids, proteins, carbohydrates, carotenoids, vitamins, biodiesel, biohydrogen, biogas, and bioplastics. These bioactive compounds can be widely used in commercial, medical, and industrial applications [2, 8, 9, 10, 11]. There are many biotechnological applications for algae in wastewater treatment plants [10]. Microalgae have significant importance for the environment. Firstly, algae have high photosynthetic efficiencies, are important as primary producers of organic matter at the base of the food chain, and provide oxygen for other aquatic life. Secondly, algae can be produced in many harsh environments not suitable for crop production, including non-arable land, saline, and wastewater. Commonly used biomasses, such as algae, also contain components such as protein, carbohydrates, and pigments [7, 8, 9, 10, 12].

The future vision is to search for sustainable alternative solutions with friendly environmental properties that focus on algae, which is one of the available and sustainable solutions with its multiple applied uses in the fields of environment, industry, cosmetics, food supplements, medicine, etc. [13, 14]. The fact that algae are present in all environments plays an important role in the various vital processes and treatment processes [5, 15]. Therefore, this study must search for the presence of algae in this chosen environment. Therefore, the use of these effluents for the cultivation of microalgae can be interesting for the economic sustainability of the cultivation stage of algae and for environmental sustainability through the biological treatment application of the effluents forever [1, 5, 10].

Physical and chemical measurements are quantitative data that mention the presence and levels of aquatic pollution and degradation [16]. Algal aggregates are sensitive to certain pollutants that may easily accumulate within algal cells, and their metabolism within algae is also sensitive to diverse environmental and natural disturbances [17]. Several conducted studies included the presence and uses of some genus of microalgae in the effluent of wastewater and their applications, such as Nining in 2023 [18]; Mustafayeva in 2023 [19]; Senem et al., in 2020 [20]; Trevore et al., in 2019 [1]; Min Su., et al., in 2017 [21]; Wang et al., in 2016 [22]; Mahdy et al., in 2016 [23]; Ebrahimian et al., in 2014 [24]; Kumar and Chopra, in 2012 [25]; Borowitzka in 2013 [26]; Wang et al., in 2010 [27]; and Aach, 1952 [28]; those microalgae were Chlorella vulgaris and Dunaliella sp. And microalgae were used as renewable source for treating wastewater in the biological treatment stage as shown in the study by Wang et al. [29].

The first use of microalgae in the world dates back 2000 years to the Chinese, who used Nostoc algae during famine to survive. Microalgae biotechnology is the window to development in finding alternative and sustainable scientific solutions, which only began to appear in the middle of the last century. It has been noted that there are many commercial advertisements that use algae applications, such as microalgae in wastewater treatment [29, 30].

More studies were applied to microalgae in such applications and found to be higher than others in the classification of algae at the FB Meeting Jr. in 1996 [31]. This study of the biodiversity of algae is the first interest in Yemen as a future vision to search for sustainable alternative solutions with friendly environmental properties. In which it aimed to screen and identify the family of microalgae at the station of the sewage treatment plant and its channel length, with screening three parameters for each sample region as the primary study for more conducting studies and applications of microalgae in the area of study for wastewater treatment and other applications as soon as possible.

2. Materials and methods

2.1 Study area

The study area aimed at the Sewage Treatment Plant and its channel length during the period from the end months of the second quarter of 2021 and the first months of the third quarter of 2021 to identify the biodiversity of algae and screen three physical and chemical parameters (temperature, pH, and total dissolved salt) of the station and its channel length. As shown in the following Figure 1, this study targeted the sewage treatment plant located in the northern region and its channels located along the course of the sewage channel of the sewage treatment plant north of the capital, Sana’a, with an estimated length of about 20 km to the north [33]. About 95% of the irrigation crops in the study area rely on wastewater coming out of the sewage treatment plant in Sana’a that farmers use to irrigate their farms directly [33, 34]. The wastewater corridor in the Sana’a Basin starts at the outlet of the Sana’a City Wastewater Treatment Plant on the northern edge of the Sana’a Basin (Arhab and Bani al-Harith areas), and both treated and untreated sewage flows together in the channel, which is about 2.5 meters wide [35].

Figure 1.

Location and topographic map of the Sana’a basin Basin (study area) [digital elevation map from a satellite dataset [32].

2.2 Sampling area

Along with the sewage treatment plant’s tanks, samples were chosen to encompass nearly the whole wastewater channel stream in the research region. As shown in the accompanying Table 1, the sampling locations were between latitudes and longitudes of 29.5239^15̍N-36.3065^15̍N and 044.134912^ÍE- 04414.8938^ÍE.

Sample region		Sample No.	Type of region	latitudes	longitudes
Collection sample of aeration tanks		1	Aeration tank	29.5239°15̍N	044.134912˚̍E
Collection sample of sedimentation tanks	WWTP- Sana’a(Sana’a wastewater treatment plant)	2	sedimentation tanks	29.8071°15̍N	04413.5310˚̍E
drying beds		3	drying beds	29.8298°15̍N	04413.5221˚̍E
Swamp channel initiation 1	regions along wastewater channel in Bani Alhareth and Arhab	4	wastewater pond along sewage channel; Sewage	29.2856°15̍N	04413.8727˚̍E
Swamp channel initiation 2		5		29.3086°15̍N	04413.8771˚̍E
Swamp channel initiation 3		6		29.5045°15̍N	04413.8618˚̍E
Bait alhellali		7		29.5910°15̍N	04413.7606˚̍E
Bait alqaidi		8		29.6273°15̍N	04413.7595˚̍E
Bait Quhaim		9		29.6590°15̍N	04413.7450˚̍E
Bait handhal		10		29.8841°15̍N	04413.6110˚̍E
Bait senhoub		11		30.0009°15̍N	04413.6035˚̍E
Bait Haroon		12		32.8591°15̍N	04413.5365˚̍E
Alssama Dam		13		36.3065°15̍N	04414.8938˚̍E

Table 1.

Collected sample regions.

2.3 Collection of water samples

Glass, polyethylene, and plastic bottles are non-sterile, hygienic, dry, and leak-proof [36]. The following procedures were used in this investigation when collecting the sample collection: Water samples should be sent as soon as possible after collection to the laboratory. Testing for algae needs to start as soon as possible after the water samples are collected, to provide the most reliable findings.

2.3.1 Analysis of the water samples microbiologically and physically

100 ml of water was filled up in a plastic container under a tightly closed and directly read as wet preparation under a light microscope with 5×, 10×, and 40× lenses times 10× according to the phycology and algae method in three replicates with determination of pH and total dissolved salts and temperature, which calculate the mean value [37, 38].

3. Results and discussion

Table 2 shows the presence of algae that belong to the Chlorophyceae class which is seen under light microscopic examination by direct wet perpetration which shows Chlorella vulgaris with ratio 100% among all collected samples, followed by Chlamedomonas reinhardtii and Kirchneriella lunaries with ratio 76.92% and the less found genus of filamentous algae was Nostoc sp., Oscillatoria phucus, Ulotrix micrasterias, Dingoflagellate ceratium, Desmedium with ratio 7.69% for each, with the mean value of temperature 28˚C; pH and total dissolved solids (TDS) were detected as shown in above table in three replicates with the mean value which shows naturalized media around 7.2 for most samples area under study and high resembles the content of TDS that appeared no treatment was done during the length of sewage channel at that year 2021 during the sample collection. The majority of the microalgae found in this study were similar to those found in the majority of the numerous studies that were conducted which play an important role in treating wastewater, as previously mentioned in reviews and literature, which discovered that Cyanobacteria—such as Chlorella vulgaris, Chlamedomonas reinhardtii, and Cladophora sp.—were the most common algae in sewage treatment plants across numerous stages. These algae were also used in numerous biotechnology applications, as reported by Hunter-Cevera et al. in 1996 [39], and Abdel-Raouf et al. in 2012 [40]. Moreover, comparable studies have been conducted that reported the presence of a particular genus of microalgae in wastewater effluent, wherever it was discovered. Examples of these studies include those conducted by Wang et al. in 2016 [22]; Ebrahimian et al. in 2014 [24]; Mahdy et al. in 2016 [23]; and Cabanelas et al. in 2013 [41]; Ardal in 2014 [42]; El-Sheekh et al. in 2012 [43]; Gao et al. in 2011 [44]; Min Su et al. in 2017 [21]; Senem O. C., et al., in 2020 [20] who discovered a Chlorella vulgaris, which is similar to the results of the present study. As well as a genus of Scendesmus obliquus mentioned in some studies done by Zhang et al., in 2014 and 2015 [45, 46]; Ruiz Martin et al., in 2010 [47]; Santos in 2017 [48]; Papazi et al. in 2013 [49]; Sethunathan et al. in 2004 [50]; and a genus of Chlamedomonas renhardtii mentioned in the following studies done by Su et al. in 2012 [51]; Hom-Diaz et al. in 2015 [52]; Wan et al. in 2020 [53]; Xie et al. in 2020 [54]. Although Diatoms were found in some studies done by Franziska Hempel et al. in 2011 [55] in Germany and Min Su et al. in 2017 [21]. In addition to the same findings from the last conducted studies, others in Australia, the USA, Thailand, Taiwan, and Mexico mentioned using microalgae in biotechnology [56, 57, 58, 59, 60, 61]. As well as a genus of Scendesmus obliquus mentioned in some studies done by Seyedeh et al. in 2021 [62]. Another similar finding was found in the following studies done by Kumar and Chopra in 2012 [25] and Palmer in 1974 [63]; Santos in 2017 [48]; Papazi et al. in 2013 [49]; Sethunathan et al. in 2004 [50] with finding a genus of Chlamedomonas renhardtii which was also used in many applications in the following studies done by Palmer in 1974 [64]; Mohammed in 1994 [65]; Hom-Diaz et al. in 2015 [52]; and Wan et al. in 2020 [53]. Although Diatoms isolated from wastewater were used in bioplastic applications done by Min Su et al. 2017 [21]; Franziska Hempel et al. 2011 [55] in Germany; Pittman et al. 2011 [63]; and Amos., [65], more studies should be done on the findings on microalgae not only for treating sewage water but for other applications that can be done in the future.

Sample No.	Replicate	mean pH value	mean TDS value	Read samples in collective
1	3	7.2	876	Chlorella vulgaris, Cosmarium spp., Cladophora surirella, Dunaliella salina, spirulina sp. Scendesmus spp. Paramecium sp., Nostoc sp. Chlamedomonas reinhardtii, Dingoflagellate ceratium, Desmedium, Gleocapsa, Oscillatoria phucus Ulotrix micrasterias.
2	3	7.2	876	Chlorella vulgaris, Cosmarium spp., Cladophora surirella, Dunaliella salina, Scendesmus spp. Paramecium sp., Chlamedomonas reinhardtii, Desmedium, Kirchneriella lunaries
3	3	7.3	876	Chlorella vulgaris, Cosmarium contructum, Chlamedomonas reinhardtii, Paramecium sp., Gleocapsa sp., Kirchneriella lunaries.
4	3	7.2	877	Chlorella vulgaris, Cosmarium contructum, Chlamedomonas reinhardtii, Paramecium sp., Gleocapsa sp., Kirchneriella lunaries.
5	3	7.2	874	Chlorella vulgaris, Cosmarium contructum, Kirchneriella lunaries.
6	3	7.2	875	Chlorella vulgaris, Chlamedomonas reinhardtii, Kirchneriella lunaries, Cylindrical clostridia
7	3	7.2	876	Chlorella vulgaris, Spirulina sp., Chlamedomonas rettenhei
8	3	7.4	873	Chlorella vulgaris, Spirulina sp., Chlamedomonas rettenhei
9	3	7.2	869	Chlorella vulgaris, Cosmarium contructum, Kirchneriella lunaries.
10	3	7.2	868	Chlorella vulgaris, Cosmarium contructum, Chlamedomonas reinhardtii, Paramecium sp., Gleocapsa sp., Kirchneriella lunaries.
11	3	7.2	870	Chlorella vulgaris, Cosmarium contructum, Kirchneriella lunaries.
12	3	7.3	874	Chlorella vulgaris, Chlamedomonas reinhardtii, Kirchneriella lunaries, Cylindrical clostridia
13	3	7.2	872	Chlorella vulgaris, Chlamedomonas reinhardtii, Kirchneriella lunaries, Cylindrical closteridia

Table 2.

Shows the presence of microalgae and three parameters of each sample region.

4. Conclusion

The findings appeared to indicate that the role of algae presence in the study area in despite of no treatment has been done on the Sana’a Sewage Treatment Plant of the area regarding the high TDS detected along the channel which need more studies to use algae presence for right treatment of wastewater, which will surely treat wastewater and decrease the causes of many diseases for human that deal with direct use of the channel either with using for irrigation of plants or farmers along the channel where there are no adding any aeration or supportive methods for irrigation of plants and farmers along the channel where there are no adding any aeration or supportive methods for getting beneficial from such algae grown as blooms on the surface of the channel as natural treatment which should be used for near future applications in area. Another point of view is that more available microalgae can be used in many applications, such as using the station for energy sources such as biofuel, biogas, biohydrogen, and so on, as well as for purifying sewage water using more microalgae.

5. Recommendation

• More attention is being paid to the economic role of microalgae in the treatment of sewage treatment plants to purify outlet sewage before exiting the channel through the sea pond in Sana’a STP.

• More studies should be done all the time to draw from natural resources and exploit them in practical applications for wastewater treatment and other uses.

• More investments in the study area for biotechnology applications are more needed.

Acknowledgments

We have to thank all the workers in the Sewage Treatment Plant who supported us for this study and did the experimental tests at their laboratory, and we have to mention that.

Conflicts of study

No financial support has been found for this study; we personally support it. There were some laboratory systems and apparatus not working, such as the BOD incubator, so we could not do other parameters.

Appendix

Some photos of selected regions of sampling and microalgae finding under microscopic lenses (5x;10x;40x) (Figure A1).

Figure A1.

Some photos of selected regions of sampling and microalgae finding under microscopic lenses (5x;10x;40x).