THE EFFECTS OF SEWAGE EFFLUENT ON THE WATER QUALITY OF SEPANE SPRUIT, THABA-NCHU IN FREE STATE Likeleli Koikoi, Prof. P.J. du Preez & Dr J.C. Roos

University of the Free State, Department of Plant Science, P.O. Box 339 (IB62), Bloemfontein, South Africa.

T: +27 (0)51 401 2514 dpreezpj@ufs.ac.za

IntroductionDiminishing water quality problems are serious environmental concerns throughout the world. In South Africa (SA), water resources are polluted and exploited as a result of a rapidly expanding economy and an escalating human population growth. In SA, the population grows at a rate of 1.1% per anum (statssa, 2011) and it has been extrapolated that by 2018, water resources will be exhausted to their maximum capacity (Dallas & Day, 2004). There is therefore, a need for implementation of immediate remedial and mitigation measures to redeem this situation. Water pollution by sewage effluents is a common water quality problem in SA, and so that forms the theme of this project.

This study is confined to Sepane Spruit, a stream which drains Thaba-Nchu district in the Free State province (Figure 1). This stream is a tributary of the Modder River which in turn drains the greater Bloemfontein area. The latter is the capital city of the Free State Province.

Figure 1: Vegetation map of the Free State province. Study area (Sepane Spruit within Thaba-Nchu) encircled in red.

Aims? To determine the sewage treatment efficiency of the Thaba-Nchu sewage treatment plant;? To determine the effects of the sewage effluent on the quality of the receiving water;? To determine the water quality in the Sepane Spruit and recommend remedial measures, if need be;? To determine whether water at different sites is fit for livestock watering, recreational and domestic purposes;? To contribute towards compilation of scientific data on South African water bodies for purposes of assessment,

management and future reference.

Description Of The Study AreaSepane Spruit has a total catchment area of 239 030 hacters and is confined to the Free State province.

Figure 2: A Google map of the sampling points along the length of Sepane Spruit.

The three sampling points are shown in figure 2, one at Seroale Dam (upstream), another one at the sewage treatment works and then downstream of the sewage works.

There are human settlement areas in the immediate catchment of the stream. This stream is therefore susceptible to disturbances from human activities such as small scale fishing (Bosch, 2001). The banks of the dam are disturbed and eroded due to human and livestock trampling (Figure 3). It is at this part of the stream that fishing by local people was noted.

Figure 3: View of the sampling point at Seroale Dam.

There are dump piles (Figure 4) about 300m to the northern side of the treatment works, on a relatively higher slope. These heaps are an environmental threat: it is probable that when it rains, the rubbish is swept into the stream, compromising its water quality. During windy days, the rubbish is scattered all over the area and into the stream.

Figure 4: Rubbish dumps containing solid waste from the Thaba Nchu treatment plant.

Figure 5: Solid waste separator

Figure 5 shows the primary stage of sewage treatment in which the solid suspended materials such as plastics are pulled out. Sadly, the rubbish is dumped just outside the sewage work's compound as shown by figure 4 above.

Figure 6: The final settlement

Figure 6 shows the final stage of sewage treatment, after which the effluent is discharged into the stream. Chlorine is added to the treated sewage effluent to kill micro-organisms before it is released into Sepane Spruit. The effluent is sampled at this point in order to check the efficiency of treatment. On the 21st June 2011, the effluent was released at 3.7mL/day.

Figure 7: Sepane Spruit downstream of the sewage works

This stream is quite shallow at this point (Figure 7) and it is where livestock trample and drink. On the immediate grazing areas of the stream, a great flock of grazing cattle have been noted. Water at this point is prone to pollution by animal dung and trampling.

Materials And Methods UsedTwo sets of bottles were used at each site; 200ml glass bottles for collection of microbial water samples and the 1 litre plastic bottles were used to collect chemical water samples. The microbial water samples were kept under ice in the cooler box during transportation from the site. The samples were then taken to the laboratory for analysis within 24 hours of collection. The water samples were analysed at the Institute of Ground Water Studies' laboratories, the following parameters were quantified: COD, Coliform bacteria, Phosphates, Total Nitrogen and Chlorophyll a. On the other hand, the following parameters were measured in situ at the site: temperature, DO, pH, EC and salinity.

ResultsThis project was started in June 2011 and only one set of results is presented as raw data. However, as the project progresses, the results will be presented in the form of graphs and charts.

Table1: The data collected at different sampling points in June 2011

Discussions

The pH values did not vary much within the three sites and are within the allowed limits for aquatic ecosystems. DO was particularly low at the sewage works, this indicates that the sewage effluent threatens the life of biota downstream. However, this stream has a quick oxidation capacity because the DO downstream had increased.

The microbial efficiency of Thaba-Nchu sewage works is compromised because the discharged effluent was rich in both E.coli and faecal coliforms. This effluent polluted the receiving stream water. However, downstream of the sewage works, faecal pollution may have been aggravated by cattle dungs since the sampling point was within the drinking spot.

Both phosphorus and nitrogen were found to be within the recommended limits at all points. This indicates a relatively fair water quality. These elements are important sources of eutrophication, hence their respective concentrations have to be maintained within the recommended limits at all times.

Figure 8: A normal sludge-situation

Figure 8 (taken on the 24th May 2011) indicates a normal situation in which electricity-powered motors drive sewage through the sludge.

Figure 9: Stagnant and dry sludge during electricity-cut

Figure 9 shows dry sludge on the 21st July 2011 at the Thaba-Nchu sewage works. At this time, there was a power-cut because the management had not paid the electricity dues of this station. The sewage effluent was then discharged untreated. The impacts of this ignorance and carelessness will be seen in the results of July 2011.

ConclusionThe study is only at its beginning stage, however, most water quality parameters are within the recommended limits. A profound microbial pollution was caused by the sewage effluent to the receiving stream.

REFERENCES Bosch. P.J.A.,2001. The Geology of the Thaba Nchu 2926BB 1:50 000 Scale MapSheet. Council for Geosciences Report,Pretoria.

Dallas H.F. & Day, J. A. 2004. The Effect of Water Quality Variables on aquatic Ecosystems: A Review. WRC, Pretoria. South Africa. Pp 222

Department of Water Affairs and Forestry, 1996d. South African Water Guidelines, Volume 7: Aquatic Ecosystems. Pretoria, South Africa.

www.statssa.gov.za/publications/P0302/p3022005.pdf

PARAMETER AT THE DAM(UPSTREAM) AT THE SEWAGE DOWNSTREAM RECOMMENDED STANDARDS

Temperature (0C)

11.7

13.7

11.8

Dissolved Oxygen (DO) %

92.7

53.3

96.1

pH

7.23

7.1

7.3

6.5 -

9

Electrical Conductivity (EC) mS/m

23.6

70.7

44.9

70 -

150

Salinity (mg/l)

10

5.91

10.53

Chemical Oxygen Demand (COD)

33

65

75

75

Orthophosphate (PO4) (mg/l)

<0.1

15.02

4.75

30.66

Ammonium (NH4) (mg/l)

1.13

10.59

4.09

15

Faecal coliforms (cfu/100ml)

42

>2419

>2419

1000

E. Coli (cfu/100ml)

36

>2419

>2419