Impact of discharge wastewater final effluents on the qualities of a receiving watershed in a typical rural community of the Eastern Cape Province

Transcription

1 Impact of discharge wastewater final effluents on the qualities of a receiving watershed in a typical rural community of the Eastern Cape Province Igbinosa EO and Okoh AI Applied and Environmental Microbiology Research Group (AEMREG) Department of Biochemistry and Microbiology, University of Fort Hare, Private Bag X1314, Alice 5700, South Africa

2 Introduction Sewage discharge is a major problem currently facing South Africa, and several efforts are being vigorously pursued to controlling it. Water contaminated by effluents from various sources is associated with heavy disease burden (Okoh et al., 2007). And this could influence the current shorter life expectancy in the developing countries when compared with developed nations (WHO, 2002).

3 Several studies have shown that the majority of South African wastewater treatment works find it difficult to provide adequate treatment and disinfection of effluents prior to discharge into receiving watersheds. The situation is worse in the Eastern Cape Province due to high level of poverty, low level of sanitation, and lack of appropriate infrastructure. This has led to recurrent incidences of waterborne diseases nationwide as about 80% South Africans rely on surface water for drinking and domestic uses (Venter, 2001).

4 Pegram and coworkers, (1998) reported that 43,000 South Africans die every year from diarrhoeal disease as a result of improperly treated sewages from treatment plants. The current cholera onslaught in the Southern African region is particularly noteworthy. It is also well known that water sources are subject to frequent dramatic changes in microbial and chemical qualities as a result of variety of activities on the watershed.

5 Of significance is the contributions of discharges of municipal raw waters or treated effluent at a specific point sources into the receiving water such as streams, rivers, lakes, ponds etc. (Fatoki et al., 2003). It is therefore imperative that the qualities of treated final effluent from wastewater treatment facilities are ascertained to ensure compliance to regulatory standards.

6 In this study, we evaluate the impact of the treated final effluents of a rural wastewater treatment facility in the Eastern Cape Province on the physicochemical and microbial qualities of the receiving watershed using vibrio bacteria as indicator or test pathogen. We also hypothesize that Vibrio pathogens survived the treatment process as attached planktonic biofilms.

7 Material and Methods Plant description and study site The Wastewater treatment facility is situated at geographical coordinates of 32 o S, 26 o E and approximately 1 km East of Alice town in the Eastern Cape Province of South Africa. The plant which has a design capacity of 2000 m 3 /day receives domestic sewage, some light industrial wastewater as well as run off water, and treatment is based on the activated sludge system.

8 DESCRIPTION OF STUDY SITE Fig 1: The Map of South Africa (

9 Influent Aeration tank Sedimentation tank Chlorination tank

10 The treated final effluent is discharged into the Tyume River. Sampling Water samples were collected from the treated final effluent, discharge point, 500 m downstream and upstream of the discharge point.

11 Samples were collected monthly between August 2007 and July Physicochemical analysis The ph, temperature, electrical conductivity, Total Dissolved Solids (TDS), and Dissolved Oxygen (DO) of the samples were determined onsite using a multiparameter ion specific meter (Hanna instruments, version HI9828).

12 The turbidity was measured onsite using a microprocessor turbidimeter (HACH Company, model 2100P). The concentrations of orthophosphate as P, nitrate, nitrite and chemical oxygen demand (COD) were determined in the laboratory by the standard photometric method (DWAF, 1999) using the spectroquant NOVA 60 photometer (Merck Pty Ltd).

13 Microbiological analysis One litre of the water samples was filtered through 180, 60, and 20 µm pore size nylon nets (Millipore Corp., Bedford, MA.) and The homogenates and filterate were used for enrichment and direct plating analyses for Vibrio using standard methods (Alam et al., 2006 b)

14 Table 1: Physicochemical qualities of treated final effluent and receiving water body in a rural setting of the Eastern Cape Province Parameter/Acceptable Limits Treated final effluent Discharge point 500 m Downstream discharge point 500 m Upstream discharge point ph ( ) 6.65±0.97 ( ) 6.81±0.66( ) 7.64±0.29( ) 7.72±0.27( ) Temperature (25 o C) 20.95±4.37( ) 20.76±4.1( ) 19.03±4.57 ( ) 18.75±4.58 ( ) Conductivity (250 µscm- 1 ) ±26.04 ( ) ±47.78 ( ) 311.2±128 (99-503) ± (98-541) Turbidity (5 NTU) 6.68±5.73 ( ) 5.60±2.59 ( ) 30.38±39.52 ( ) 15.17±11.61 ( ) TDS (0-450 mg/l) ±19.76 ( ) ± ( ) ±74.5 (46-267) ±79.57(46-287) DO (4-5 mg/l) 5.92±2.00 ( ) 6.06±2.08 ( ) 6.20±1.33 ( ) 6.99±3.83 ( ) COD (30 mg/l) ± (10-975) 77.66±87.07 (16-420) ± (10-905) ±153 (10-510) Nitrate (1.5 mg/l) 10.72±3.79 ( ) 11.37±3.59 ( ) 4.79±1.54 ( ) 3.62±1.19 ( ) Nitrite (0-0.5 mg/l) 0.21±0.12 ( ) 0.24±0.13 ( ) 0.18±0.11 ( ) 0.14 ± 0.07 ( ) Orthophosphate (1.0 mg/l) 3.92±1.40 ( ) 2.16±1.54 ( ±0.99 ( ) 2.57±0.67 ( ) Note: values are mean ± S.D. (minimum and maximum values are in parentheses).

15 Fig. 2: Profile of chlorine residual concentration in the final effluent Acceptable limit for domestic water mg/l.

16 Total Vibrio counts The densities of Vibrio pathogen in the final effluents and the receiving watershed varied appreciably amongst plankton sizes. Vibrio densities ranged as follows: 180 µm ( cfu ml 1 ); 60 µm ( cfu ml 1 ); 20 µm ( cfu ml 1 ); and plankton free ( cfu ml 1 ) (Fig 3 6). The presence of this presumptive pathogen in the enriched cultured is indicative of the presence of at least one cell per 100 ml of the effluent samples.

17 Fig. 3: Presumptive Vibrio (log 10 cfu/ml) counts at final effluent sampling location.

18 Fig. 4: Presumptive Vibrio (log 10 cfu/ml) counts at discharge point sampling location

19 Fig. 5: Presumptive Vibrio (log 10 cfu/ml) counts at 500 m downstream discharge point sampling location

20 Fig. 6: Presumptive Vibrio (log 10 cfu/ml) counts at 500 m upstream discharge point sampling location

21 There appears to be a relationship between Vibrio pathogens abundance and season with the highest densities occurring in the summer. Also, the occurrence of Vibrio sp. as planktonassociated confirms the role of plankton as a potential reservoir for this pathogen. Our findings suggests that the microbial qualities of the final effluents in all stations exceeded the maximum safety limit for effluent discharge by the South African and Special Standard of no microbial growth/100ml.

22 It is generally known that an increase in concentration of pollutants will occur during low flows when point sources dominate. It was also observed that non point sources of pollution contributed to the upstream discharge point of the receiving water across the season.

23 The results obtained in this study also suggest that some of the measured pollutants have localized impacts which then get diluted downstream. The presence of this potential pathogen in the effluent is a cause for concern as most people in the rural settings use this surface water for drinking, domestic and recreational purposes.

24 Conclusion This study was carried out to evaluate the efficiency of the wastewater treatment plant in terms of qualities of the final effluent prior to discharge into the environment. Our finding revealed that the treatment plant exhibited effluent qualities that met acceptable standard in some parameters, like ph and total dissolved solid (TDS).

25 We also observed that the effluents fell short of standard requirements that are critical to the provision of clean and safe water such as organic waste (measured as turbidity DO, COD, orthophosphate, nitrate, and the microbial pathogen). We conclude that the physicochemical and microbiological qualities of the receiving watershed was to a great extent adversely impacted by the inadequately treated effluents from the investigated wastewater treatment facility.

26 Recommendation There is need for regular pollution monitoring programme of surface waters in rural communities of the Eastern Cape. All agencies concerned with environmental matters in South Africa should evolve measures to check and ensure that discharged effluents comply with laid down rules and regulations.

27 Current stage of study *Molecular characterization of isolated vibrio species. * Antibiogram profile and characterization of invasive and resistance genes

28 Acknowledgement We are grateful to the National Research Foundation (NRF) of South Africa for funding this study, and to the University of Fort Hare for sponsoring our participation at this conference.

29 Thank you for your kind attention