Removal of faecal coliforms in a wastewater stabilisation pond system in Mindelo, Cape Verde

1996 ◽  
Vol 34 (11) ◽  
pp. 149-157 ◽  
Author(s):  
M. Rångeby ◽  
P. Johansson ◽  
M. Pernrup
Keyword(s):  
Waste Water ◽  
Retention Time ◽  
Domestic Wastewater ◽  
Cape Verde ◽  
Faecal Coliform ◽  
Coliform Bacteria ◽  
Faecal Coliforms ◽  
Pond System ◽  
In Series ◽  
Influent Wastewater

In Mindelo, Cape Verde, domestic wastewater is treated in a waste water stabilisation pond system with the aim of reusing the water for agricultural purposes. The conductivity in influent wastewater is high and in order to minimise an increase in the conductivity the plant is operated with as low retention time as possible. An investigation was performed over two and a half months in 1995 with the aim of finding factors that affect the removal of faecal coliform bacteria. COD, conductivity, flow, pH and faecal coliforms were then followed through the system. The results show that the die-off rate, K, is high when the pH is high. The results also indicate that the retention time seems to be the most important factor, which means that the plant has to be operated with at least 3-4 maturation ponds in series and the inlets and outlets have to be constructed in a way that avoids short-circuiting. It was also found that not only the evapuation but also chemical and/or biological reactions affect the conductivity. This phenomenon will be investigated further.

Reducing hydraulic short-circuiting in maturation ponds to maximize pathogen removal using channels and wind breaks

2003 ◽  
Vol 48 (2) ◽  
pp. 153-162 ◽  
Author(s):  
B.J. Lloyd ◽  
C.A. Vorkas ◽  
R.K. Guganesharajah
Keyword(s):  
Retention Time ◽  
Hydraulic Retention Time ◽  
Plug Flow ◽  
Surface Flow ◽  
Faecal Coliform ◽  
Coliform Bacteria ◽  
Faecal Coliforms ◽  
Log Reduction ◽  
Time Flow ◽  
The Impact

This paper reports the impact of four sequential maturation pond interventions on the removal of thermotolerant “faecal” coliform bacteria at a full scale WSP system in tropical Colombia. Each intervention was designed to increase hydraulic retention time and was followed by continuous physico-chemical logging and meteorological monitoring, and simultaneous tracer studies to define hydraulic retention time, flow paths and dispersion. Inlet and outlet monitoring showed that, primarily due to hydraulic short-circuiting, the open maturation pond only achieved a 90% reduction in thermotolerant “faecal” coliforms. By contrast, an in-pond batch decay rate study for thermotolerant faecal coliforms showed that a 1 log (90%) reduction was achieved every 24 hours for 4 days at 26°C, so that the maximum theoretical efficiency would be a 2.6 log reduction (99.7%) if hydraulic efficiency was perfect for plug flow. The second intervention was the conversion of the maturation pond to a parallel series of three open channels to attempt to control short-circuiting and convert to plug flow. The channels raised performance to 96%. The introduction of top baffles, at the end of the first and second channels, to attempt to further reduce the effect of surface and sub-surface flow on short-circuiting, actually reduced performance to 92.64%, and were removed. The final intervention, a 2.1 m high wind break around the maturation channels raised efficiency to 98.13%; this performance is almost a half log (0.47) greater than the efficiency (95.1%) predicted from Marais' equation for a completely mixed reactor, and 0.77 log greater than recorded in the open pond. The results have fundamental implications for improving WSP efficiency, for meeting re-use guidelines, for savings in land area and improvement of design of WSPs; they also highlight short-comings in the indiscriminate use of the Marais design equation for faecal coliform removal.

Taenia eggs in a stabilization pond system with poor hydraulics: concern for human cysticercosis?

2013 ◽  
Vol 68 (12) ◽  
pp. 2698-2703 ◽  
Author(s):  
Matthew E. Verbyla ◽  
Stewart M. Oakley ◽  
Louis A. Lizima ◽  
Jie Zhang ◽  
Mercedes Iriarte ◽  
...  
Keyword(s):  
Retention Time ◽  
Hydraulic Retention Time ◽  
Taenia Solium ◽  
Treated Wastewater ◽  
Human Consumption ◽  
Dynamics Modeling ◽  
Hydraulic Residence Time ◽  
Stabilization Pond ◽  
Pond System ◽  
In Series

The objective of this study is to compare the removal of Taenia eggs to the removal of Ascaris eggs in a wastewater stabilization pond system consisting of three ponds in series, where the hydraulic residence time distribution has been characterized via a tracer study supported by computational fluid dynamics modeling. Despite a theoretical hydraulic retention time of 30 days, the peak dye concentration was measured in the effluent of the first pond after only 26 hours. The smaller-sized Taenia eggs were detected in higher concentrations than Ascaris eggs in the raw wastewater. Ascaris eggs were not detected in the pond system effluent, but 45 Taenia eggs/L were detected in the system effluent. If some of these eggs were of the species Taenia solium, and if the treated wastewater were used for the irrigation of crops for human consumption, farmers and consumers could potentially be at risk for neurocysticercosis. Thus, limits for Taenia eggs in irrigation water should be established, and precautions should be taken in regions where pig taeniasis is endemic. The results of this study indicate that the theoretical hydraulic retention time (volume/flow) of a pond is not always a good surrogate for helminth egg removal.

Removal of bacterial and viral faecal indicator organisms in a waste stabilization pond system in Choconta, Cundinamarca (Colombia)

2002 ◽  
Vol 45 (1) ◽  
pp. 61-66 ◽  
Author(s):  
C. Campos ◽  
A. Guerrero ◽  
M. Cárdenas
Keyword(s):  
Domestic Wastewater ◽  
Epidemiological Studies ◽  
Indicator Organisms ◽  
Bacterial Indicators ◽  
Stabilization Pond ◽  
Waste Stabilization Pond ◽  
Pond System ◽  
Waste Stabilization ◽  
In Series ◽  
Viral Indicators

A major objective for domestic wastewater treatment using waste stabilization pond systems is the removal of pathogenic microorganisms. Traditional evaluation parameters for faecal contamination are the total and faecal coliforms. However, epidemiological studies, environmental resistance and the behaviour in the treatment systems, show that viruses are an important disease agent and even more resistant to disinfection than bacteria. Therefore, it is important to introduce viruses as a faecal indicator and to compare them with the traditional bacterial indicators. A waste stabilization pond system was evaluated in the municipality of Chocontá, Cundinamarca (Colombia), for the removal of faecal indicators (such as Escherichia coli, Streptococcus faecalis, Clostridium perfringens) and viruses like F+, somatic and Bacteroides fragilis phages. The system includes two facultative ponds in series with a flow of 1555 m3/day. Samples were collected at the entrance of the system, in the two ponds and from the final effluent. Results show a decrease between 0.3 and 4.7 logarithmic units in the bacterial indicators and between 1 and 4.6 logarithmic units with viral indicators.

The influence of pond geometry and configuration on facultative and maturation waste stabilisation pond performance and efficiency

1995 ◽  
Vol 31 (12) ◽  
pp. 129-139 ◽  
Author(s):  
H. W. Pearson ◽  
D. D. Mara ◽  
H. A. Arridge
Keyword(s):  
Faecal Coliform ◽  
Design Approach ◽  
Design Equation ◽  
Faecal Coliforms ◽  
Land Area ◽  
Effluent Quality ◽  
In Series

Differences in length:breadth ratios (in the range of 1:1 to 6:1) and depths (from 1 to 2 m) had little effect on the performance and effluent quality (i.e. BOD, SS and FC) of secondary facultative ponds. Shallow maturation ponds (0.4 m) were more efficient at microbiological disinfection than deeper ones and could actually reduce land area requirements. KT values for faecal coliforms, salmonellae and rotavirus differed from one another in the same ponds and for different pond types. The Marais design equation for predicting faecal coliform numbers in pond effluents, although not perfect, does provide a reasonable design approach for systems containing more than two ponds in series.

Low-cost upgrading of an over-sized waste water stabilisation pond system in Mindelo, Cape Verde

1996 ◽  
Vol 33 (7) ◽  
pp. 99-106 ◽  
Author(s):  
Per Johansson ◽  
Marie Pernrup ◽  
Mikael Rångeby
Keyword(s):  
Waste Water ◽  
Sea Water ◽  
Low Cost ◽  
Treatment Plant ◽  
Cape Verde ◽  
Operational Strategies ◽  
Pond System ◽  
Almost All ◽  
The City ◽  
Interesting Alternative

Water is scarce in Cape Verde. In the city Mindelo almost all fresh water has to be produced by desalination of sea water. In this perspective, reuse of treated waste water for agricultural purposes is a very interesting alternative. The waste water stabilisation pond system in Mindelo is over-sized, with high evaporation and increasing salinity in the effluent water as a result. The salinity is already very high in the influent and with present process configuration the effluent is unusable for irrigation. The treatment plant has to be operated with less surface area to minimise the evaporation. This, on the other hand, means that an acceptable bacteriological quality in the effluent will not be achieved. By subdividing the ponds with removable plastic tarpaulins, a much smaller volume is needed to achieve this. The plastic tarpaulin can be moved and the process may be configured to different influent flows. The technique of subdividing ponds with a plastic tarpaulin is achieved at low cost and is very simple. The bacterial die-off constant, K, in the maturation ponds has been found to be around 2.65 d−1 at 26°C, which is comparable to results determined elsewhere. The bacterial die-off constant in the anaerobic pond was found to be much lower, 0.3 d−1. Operational strategies for different flows are presented.

An integrated duckweed and algae pond system for nitrogen removal and renovation

1998 ◽  
Vol 38 (1) ◽  
pp. 335-343 ◽  
Author(s):  
Peter van der Steen ◽  
Asher Brenner ◽  
Gideon Oron
Keyword(s):  
Regression Analysis ◽  
Organic Compounds ◽  
Nitrogen Removal ◽  
Domestic Wastewater ◽  
Dry Weight ◽  
Pond Water ◽  
Ammonium Concentration ◽  
Ammonium Removal ◽  
Pond System ◽  
In Series

An integrated pond system, consisting of duckweed and algae ponds, was investigated for duckweed production and for further treatment of anaerobically treated domestic wastewater. The system consisted of 10 ponds in series, arranged in 3 stages of 2 duckweed ponds, 3 algae ponds and 5 duckweed ponds, respectively. Production of duckweed ranged from 7.4-16.4 g/(m2.day) (or 27-60 ton/(ha.year)) dry weight in the first pond, to 2.7-8.2 g/(m2.day) (or 10-30 ton/(ha.year)) in the last pond. Regression analysis suggested that the production was positively influenced by the concentration of organic compounds in the pond water. The ammonium concentration in the range of 20-60 mg/l NH4-N did not affect duckweed production. Fifty-six percent of the pond influent nitrogen, mainly ammonium, was removed. Ammonium removal was due to uptake by the duckweed plants (18%), nitrification (3%), sedimentation (8%) and combined volatilization of NH3 and denitrification (73%).

Development of a land limited wastewater treatment plant for small and rural communities in the tropics

1994 ◽  
Vol 29 (12) ◽  
pp. 1-12
Author(s):  
P. Y. Yang ◽  
H. Chen ◽  
T. Ma
Keyword(s):  
Nitrogen Removal ◽  
Retention Time ◽  
Loading Rate ◽  
Domestic Wastewater ◽  
Treatment System ◽  
Synthetic Wastewater ◽  
Pond System ◽  
Fixed Film ◽  
Removal Efficiencies ◽  
Actual Wastewater

The treatment systems for strict and moderate land limited approaches were investigated. Both synthetic glucose and actual wastewater (domestic wastewater) were studied. For the strict land limited approach, a packed entrapped mixed microbial cell (PEMMC) process using cellulose triacetate as the polymer carrier was tested for synthetic wastewater. For the moderate land limited approach, a combined aquatic weed on the water surface and a bio-fixed film in the lower portion of the pond system was investigated for both the synthetic and actual wastewater. The actual domestic wastewater was examined in a single pond system with vertical flow under the BOD5 loading rate of 135 Kg/ha/day. BOD5 and nitrogen removal efficiencies of more than 85% and 70%, respectively, were received. The glucose synthetic wastewater was examined in a single pond system with horizontal flow at a BOD5 loading rate of 130 Kg/ha/day. BOD5 and nitrogen removal efficiencies of 92% and 60%, respectively, were received. For the strict land limited treatment approach, it was found that more than 90% and 85% of soluble COD and total COD (including effluent suspended solid), respectively, could be removed at the loading rate of 1.6 g COD/L/day. The hydraulic retention time of 3.5 hours and the influent COD concentration of 200-250 mg/L were maintained and operated. This is comparable with the process performance of the conventional activated sludge for treating the domestic sewage under the same operational conditions. The PEMMC process also provides the advantages of maintaining a high SRT (Solid Retention Time) without external sludge recycling and a short starting period of less than 10 days. Application of the present two systems will be dependent on the land and/or energy requirement. It is appropriate to use the treatment system of combining the aquatic plant with the bio-fixed film for moderately available land and in tropical areas. A strict land limited treatment system, of course, requires additional energy input.

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