Wastewater treatment performance efficiency of constructed wetlands in African countries: a review

2014 ◽  
Vol 71 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Andualem Mekonnen ◽  
Seyoum Leta ◽  
Karoli Nicholas Njau
Keyword(s):  
Wastewater Treatment ◽  
Constructed Wetland ◽  
Oxygen Demand ◽  
Surface Flow ◽  
Operational Parameters ◽  
Treatment Efficiency ◽  
African Countries ◽  
Wetland Type ◽  
Treatment Performance ◽  
Nutrient Removal Efficiency

In Africa, different studies have been conducted at different scales to evaluate wastewater treatment efficiency of constructed wetland. This paper aims to review the treatment performance efficiency of constructed wetland used in African countries. In the reviewed papers, the operational parameters, size and type of wetland used and the treatment efficiency are assessed. The results are organized and presented in six tables based on the type of wetland and wastewater used in the study. The results of the review papers indicated that most of the studies were conducted in Tanzania, Egypt and Kenya. In Kenya and Tanzania, different full-scale wetlands are widely used in treating wastewater. Among wetland type, horizontal subsurface flow wetlands were widely studied followed by surface flow and hybrid wetlands. Most of the reported hybrid wetlands were in Kenya. The results of the review papers indicated that wetlands are efficient in removing organic matter (biochemical oxygen demand and chemical oxygen demand) and suspended solids. On the other hand, nutrient removal efficiency appeared to be low.

scholarly journals Treatment of Piggery Wastewater by Three Grass Species Growing in a Constructed Wetland

2017 ◽  
pp. 75-83 ◽  
Author(s):  
Supaporn Pongthornpruek
Keyword(s):  
Wastewater Treatment ◽  
Constructed Wetland ◽  
Retention Time ◽  
Hydraulic Retention Time ◽  
Oxygen Demand ◽  
Surface Flow ◽  
Grass Species ◽  
Vetiver Grass ◽  
Piggery Wastewater ◽  
Wastewater Quality

The study aimed to investigate the efficiency of piggery wastewater treatment by the surface flow constructed wetland with three different grass species; bulrush (Scirpus spp.), cattail (Typha angustifoliaL.), and vetiver grass (Vetiveria zizanioides L.). All pilot units were used for wastewater treatment by the flowing surface water system, giving a system carrying capacity of several 0.18 m3 d-1 of HLR with a 5 day hydraulic retention time (HRT). The results showed that the cattail pilot showed improvement in several wastewater quality indicators: biochemical oxygen demand (BOD), chemical oxygen demand (COD) and total kjeldahl nitrogen (TKN) with efficiencies of 80.59, 84.11 and 88.08 %, respectively. The vetiver grass was most efficient of the three grasses in treating total phosphorus (TP). The efficiency of constructed wetland treatment using bulrush and cattail for TP was not significantly different. The piggery wastewater treatment with a 5 day HRT was able to reduce the dirtiness in wastewater but ultimately was unable to meet the wastewater quality standard. Thus, the periods for hydraulic retention time should be increased to establish the optimal retention time for effective wastewater treatment.

Evaluating the treatment performance of a full scale Activated Sludge Plant in Islamabad, Pakistan

2012 ◽  
Vol 7 (1) ◽  
Author(s):  
S. S. Fatima ◽  
S. Jamal Khan
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Wastewater Treatment Plant ◽  
Suspended Solids ◽  
Treatment Plant ◽  
Oxygen Demand ◽  
Full Scale ◽  
Operational Parameter ◽  
Mixed Liquor ◽  
Treatment Performance

In this study, the performance of wastewater treatment plant located at sector I-9 Islamabad, Pakistan, was evaluated. This full scale domestic wastewater treatment plant is based on conventional activated sludge process. The parameters which were monitored regularly included total suspended solids (TSS), mixed liquor suspended solids (MLSS), mixed liquor volatile suspended solids (MLVSS), biological oxygen demand (BOD), and chemical oxygen demand (COD). It was found that the biological degradation efficiency of the plant was below the desired levels in terms of COD and BOD. Also the plant operators were not maintaining consistent sludge retention time (SRT). Abrupt discharge of MLSS through the Surplus Activated sludge (SAS) pump was the main reason for the low MLSS in the aeration tank and consequently low treatment performance. In this study the SRT was optimized based on desired MLSS concentration between 3,000–3,500 mg/L and required performance in terms of BOD, COD and TSS. This study revealed that SRT is a very important operational parameter and its knowledge and correct implementation by the plant operators should be mandatory.

scholarly journals The Effectiveness of Organic Pollutants Removal in Constructed Wetland with Horizontal Sub-Surface Flow / Efektywność Usuwania Zanieczyszczeń Organicznych W Oczyszczalni Hydrofitowej

2015 ◽  
Vol 16 (1) ◽  
pp. 69-82 ◽  
Author(s):  
Anita Jakubaszek ◽  
Zofia Sadecka
Keyword(s):  
Wastewater Treatment ◽  
Organic Pollutants ◽  
Constructed Wetland ◽  
Suspended Solids ◽  
Research Work ◽  
Vegetation Period ◽  
Surface Flow ◽  
Seasonal Temperature ◽  
Work Related ◽  
Pollutants Removal

Abstract This paper presents the results of the research work related to the removal efficiency from wastewater organic pollutants and suspended solids at HSSF (horizontal subsurface flow) constructed wetland. The average effectiveness defined as loss of value COD in wastewater has reached 77%, for BOD5 - 80% and TOC - 82%. The effect of seasonal temperature changes and the period of plant vegetation and rest on the effectiveness of wastewater treatment were also analyzed. The results of the presented research showed a decrease in the efficiency of removing organic pollutants from wastewater and suspended solids in the autumn and winter. During the vegetation the object in Małyszyn has been characterized by the effectiveness of wastewater treatment at the level of 78% for COD, 82% for BOD5, and in the non-vegetation period the effectiveness has decreased up to 75% for COD and 74% for BOD5. During the plants growth the total suspension was removed in 88%, whereas during the plants rest efficiency of removing lowered to 69%.

scholarly journals Spatial variation of physicochemical parameters in a constructed wetland for wastewater treatment: An example of the use of the R programming language

2021 ◽  
Vol 13 (1) ◽  
pp. 15
Author(s):  
Junior Pastor Pérez-Molina ◽  
Carola Scholz ◽  
Roy Pérez-Salazar ◽  
Carolina Alfaro-Chinchilla ◽  
Ana Abarca Méndez ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Spatial Variation ◽  
Water Flow ◽  
Programming Language ◽  
Constructed Wetland ◽  
Physicochemical Parameters ◽  
Preferential Flow ◽  
Oxygen Demand ◽  
R Programming Language ◽  
R Programming

Introduction: The implementation of wastewater treatment systems such as constructed wetlands has a growing interest in the last decade due to its low cost and high effectiveness in treating industrial and residential wastewater. Objective: To evaluate the spatial variation of physicochemical parameters in a constructed wetland system of sub-superficial flow of Pennisetum alopecuroides (Pennisetum) and a Control (unplanted). The purpose is to provide an analysis of spatial dynamic of physicochemical parameters using R programming language. Methods: Each of the cells (Pennisetum and Control) had 12 piezometers, organized in three columns and four rows with a separation distance of 3,25m and 4,35m, respectively. The turbidity, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), ammoniacal nitrogen (N-NH4), organic nitrogen (N-org.) and phosphorous (P-PO4-3) were measured in water under in-flow and out-flow of both conditions Control and Pennisetum (n= 8). Additionally, the oxidation-reduction potential (ORP), dissolved oxygen (DO), conductivity, pH and water temperature, were measured (n= 167) in the piezometers. Results: No statistically significant differences between cells for TKN, N-NH4, conductivity, turbidity, BOD, and COD were found; but both Control and Pennisetum cells showed a significant reduction in these parameters (P<0,05). Overall, TKN and N-NH4 removal were from 65,8 to 84,1% and 67,5 to 90,8%, respectively; and decrease in turbidity, conductivity, BOD, and COD, were between 95,1-95,4%; 15-22,4%; 65,2-77,9% and 57,4-60,3% respectively. Both cells showed ORP increasing gradient along the water-flow direction, contrary to conductivity (p<0,05). However, OD, pH and temperature were inconsistent in the direction of the water flow in both cells. Conclusions: Pennisetum demonstrated pollutant removal efficiency, but presented results similar to the control cells, therefore, remains unclear if it is a superior option or not. Spatial variation analysis did not reflect any obstruction of flow along the CWs; but some preferential flow paths can be distinguished. An open-source repository of R was provided. 

Constructed wetland for water quality improvement: a case study from Taiwan

2010 ◽  
Vol 62 (10) ◽  
pp. 2408-2418 ◽  
Author(s):  
C. Y. Wu ◽  
J. K. Liu ◽  
S. H. Cheng ◽  
D. E. Surampalli ◽  
C. W. Chen ◽  
...  
Keyword(s):  
Water Quality ◽  
Wastewater Treatment ◽  
Constructed Wetlands ◽  
Constructed Wetland ◽  
Water Reuse ◽  
Oxygen Demand ◽  
Sediment Oxygen Demand ◽  
Nucleotide Sequence Analysis ◽  
Sediment Samples ◽  
Wetland System

In Taiwan, more than 20% of the major rivers are mildly to heavily polluted by domestic, industrial, and agricultural wastewaters due to the low percentage of sewers connected to wastewater treatment plants. Thus, constructed or engineered wetlands have been adopted as the major alternatives to clean up polluted rivers. Constructed wetlands are also applied as the tertiary wastewater treatment systems for the wastewater polishment to meet water reuse standards with lower operational costs. The studied Kaoping River Rail Bridge Constructed Wetland (KRRBCW) is the largest constructed wetland in Taiwan. It is a multi-function wetland and is used for polluted creek water purification and secondary wastewater polishment before it is discharged into the Kaoping River. Although constructed wetlands are feasible for contaminated water treatment, wetland sediments are usually the sinks for organics and metals. In this study, water and sediment samples were collected from the major wetland basins in KRRBCW. The investigation results show that more than 97% of total coliforms (TC), 55% of biochemical oxygen demand (BOD), and 30% of nutrients [e.g. total nitrogen (TN), total phosphorus (TP)] were removed via the constructed wetland system. However, results from the sediment analyses show that wetland sediments contained high concentrations of metals (e.g. Cu, Fe, Zn, Cr, and Mn), organic contents (sediment oxygen demand = 1.7 to 7.6 g O2/m2 d), and nutrients (up to 18.7 g/kg of TN and 1.22 g/kg of TN). Thus, sediments should be excavated periodically to prevent the release the pollutants into the wetland system and causing the deterioration of wetland water quality. Results of polymerase chain reaction (PCR), denaturing gradient gel electrophoresis (DGGE), and nucleotide sequence analysis reveal that a variation in microbial diversity in the wetland systems was observed. Results from the DGGE analysis indicate that all sediment samples contained significant amounts of microbial ribospecies, which might contribute to the carbon degradation and nitrogen removal. Gradual disappearance of E. coli was also observed along the flow courses through natural attenuation mechanisms.

scholarly journals Mathematical Modeling of a Domestic Wastewater Treatment System Combining a Septic Tank, an Up Flow Anaerobic Filter, and a Constructed Wetland

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3019
Author(s):  
Alberto Fernández del Castillo ◽  
Marycarmen Verduzco Garibay ◽  
Carolina Senés-Guerrero ◽  
Carlos Yebra-Montes ◽  
José de Anda ◽  
...  
Keyword(s):  
Mathematical Modeling ◽  
Wastewater Treatment ◽  
Linear Regression ◽  
Multiple Linear Regression ◽  
Mass Balance ◽  
Constructed Wetland ◽  
Oxygen Demand ◽  
Septic Tank ◽  
First Order ◽  
Mass Balance Models

Systems combining anaerobic bioreactors with constructed wetlands (CW) have proven to be adequate and efficient for wastewater treatment. Detailed knowledge of removal dynamics of contaminants can ensure positive results for engineering and design. Mathematical modeling is a useful approach to studying the dynamics of contaminant removal in wastewater. In this study, water quality monitoring was performed in a system composed of a septic tank (ST), an up flow anaerobic filter (UAF), and a horizontal flow constructed wetland (HFCW). Biological oxygen demand (BOD5), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), NH3, organic nitrogen (ON), total suspended solids (TSS), NO2−, and NO3− were measured biweekly during a 3-month period. First-order kinetics, multiple linear regression, and mass balance models were applied for data adjustment. First-order models were useful to predict the outlet concentration of pollutants (R2 > 0.87). Relevant multiple linear regression models were found, which could be applied to facilitate the system’s monitoring and provide valuable information to control and improve biological and physical processes necessary for wastewater treatment. Finally, the values of important parameters (μmax, Ks,  and Yx/s) in mass-balance models were determined with the aid of a differential neural network (DNN) and an optimization algorithm. The estimated parameters indicated the high robustness of the treatment system since performance stability was found despite variations in wastewater composition.

Horizontal sub-surface flow constructed wetland with pulsing water level

2003 ◽  
Vol 48 (5) ◽  
pp. 143-148 ◽  
Author(s):  
J. Vymazal ◽  
M. Masa
Keyword(s):  
Water Level ◽  
Constructed Wetland ◽  
Municipal Wastewater ◽  
Water Discharge ◽  
Experimental Period ◽  
Surface Flow ◽  
Treatment Efficiency ◽  
Outflow Velocity ◽  
In Series ◽  
Positive Effect

A constructed wetland with horizontal sub-surface flow at Dolni Mesto (Czech Republic) was put into operation in 1999 and treats municipal wastewater from 522 PE. The total area of vegetated beds of 2,646 m2 is divided into two parallel sections of equal size, each with two beds in series. Between two periods of water discharge there is no outflow from the bed. During the period of September 1999-September 2000 one bed was operated with a pulsing water level while the other one was not pulsing, i.e., was operated as regular sub-surface flow in order to evaluate the effect of pulsing on treatment efficiency, especially on removal of NH4-N. Between September 1999 and February 2000 the pulse was 8 cm, for the rest of the experimental period the pulse was 15 cm. The results indicate a positive effect of pulsing on removal of BOD5 (annual average of 53%), COD (30%) and NH4-N (27%) as compared to non-pulsing beds. For SS, a decrease in removal effect by 30% was observed. This is probably due to the higher outflow velocity of discharged water from pulsing beds which can flush out settled particles. The results also indicate that a pulsing level of 15 cm was more efficient than 8 cm.

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