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.

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.

Removal of Total Coliform and TSS for Hospital Wastewater by Optimizing the Role of Typha Angustifolia and Fine Sand-Gravel Media in Horizontal Sub Surface Flow Constructed Wetland

2021 ◽  
Vol 12 (1) ◽  
pp. 20-31
Author(s):  
Abdul Gani Akhmad
Keyword(s):  
Retention Time ◽  
Hydraulic Retention Time ◽  
Fine Sand ◽  
Pilot Scale ◽  
Total Coliform ◽  
Surface Flow ◽  
Pollutant Removal ◽  
Typha Angustifolia ◽  
Hospital Wastewater

This study aims to evaluate the performance of a pilot-scale HSSF-CW utilizing Typha angustifolia and fine sand-gravel media in removing total coliform and TSS from hospital wastewater. Three pilot-scale HSSF-CW cells measuring 1.00 x 0.45 x 0.35 m3 were filled with gravel sand media with a diameter of 5 - 8 mm as high as 35 cm with a submerged media depth of 0.30 m. There were three treatments, namely the first cell (CW1) without plants, the second cell (CW2) was planted with a density of 12 Typha angustifolia plants, and the third cell (CW3) was planted with a density of 24 Typha angustifolia plants. The three HSSF-CW cells received the same wastewater load with total coliform and TSS contents of 91000 MPN / 100 mg and 53 mg / L, respectively, with Hydraulic Loading Rates 3,375 m3 per day. Wastewater was recirculated continuously to achieve the equivalent HSSF-CW area requirement. The experimental results show that the performance of CW3 is more efficient than CW1 and CW2 in total coliform and TSS removal for hospital wastewater. The pollutant removal efficiency at CW3 reached 91.76% for total coliform with one day hydraulic retention time and 81.00% for TSS with two days of hydraulic retention time. This study concludes that the HSSF-CW system using sand-gravel media with a diameter of 5 - 8 mm with a submerged media depth of 0.30 m and planted with Typha angustifolia with a tighter spacing proved to be more efficient in removing total coliform and TSS from hospital wastewater.

Two-Phase Mesophilic Anaerobic Co-Digestion of Food Waste and Sewage Sludge: Effect of Hydraulic Retention Time

2014 ◽  
Vol 852 ◽  
pp. 789-796 ◽  
Author(s):  
Guo Hua Wang ◽  
Lei Wang ◽  
Xue Jun Tan ◽  
Yi Xian Wang ◽  
Feng Wang
Keyword(s):  
Anaerobic Digestion ◽  
Sewage Sludge ◽  
Food Waste ◽  
Retention Time ◽  
Hydraulic Retention Time ◽  
Removal Rate ◽  
Two Phase ◽  
Acidogenic Reactor ◽  
In Series ◽  
The Impact

The impact of hydraulic retention time (HRT) on two-phase mesophilic (35°C) anaerobic co-digestion of food waste and sewage sludge was studied under mixing ratio of 1:1 on the TS basis. Laboratory-scale, two-phase anaerobic digestion systems were employed with each system consisting of an acidogenic reactor and a methanogenic reactor linked in series. For the acidogenic phase, an increase of volatile fatty acid (VFA) concentration was observed as HRT increased from 1d to 5d and the HRT of 5d was recommended for significantly higher VFA production and less propionate percentage, which could provide stable and favourable substrates for the methane reactor. Under acidogenic HRT of 5d, 20d was proved to be the optimum HRT for methanogenic phase with the methane content, methane production rate, methane yield and two-phase VS removal rate reached 71%, 0.7L/(L·d), 0.69L/gVSremoved and 64.7%, respectively. Results verified that the constraints of conventional anaerobic digestion for food waste or sewage sludge separately could be overcome by synergistic effect of co-digestion strategy and two-phase treatment.

The effect of hydraulic retention time on the removal of pollutants from sewage treatment plant effluent in a surface-flow wetland system

Wetlands ◽  
10.1672/13 ◽  
2005 ◽  
Vol 25 (2) ◽  
pp. 375-391 ◽  
Author(s):  
Sylvia Toet ◽  
Richard S. P. Logtestijn ◽  
Ruud Kampf ◽  
Michiel Schreijer ◽  
Jos T. A. Verhoeven
Keyword(s):  
Retention Time ◽  
Hydraulic Retention Time ◽  
Sewage Treatment ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
Surface Flow ◽  
Wetland System

scholarly journals Impact of hydraulic retention time on phosphorus removal from wastewater using reactive media

2020 ◽  
Vol 82 (12) ◽  
pp. 2920-2928
Author(s):  
S. Benzing ◽  
F. Couceiro ◽  
S. Barnett ◽  
J. B. Williams ◽  
P. Pearce ◽  
...  
Keyword(s):  
Retention Time ◽  
Hydraulic Retention Time ◽  
Wastewater Treatment Plants ◽  
Appropriate Technology ◽  
Synthetic Wastewater ◽  
Depth Analysis ◽  
The Impact ◽  
Over Time ◽  
P Removal ◽  
Reactive Media

Abstract Phosphorus (P) discharge from wastewater treatment plants into the environment contributes to eutrophication issues. Reactive media filters represent an effective, simple and cost-effective solution to decrease the P content. Previous research used various experimental designs and often synthetic wastewater, making assessment of real-world performance difficult. This study assesses the impact of the hydraulic retention time (HRT) on P removal using real wastewater to refine design criteria for full-scale installations. Four media were compared in column experiments for >200 days. Different HRTs were applied and initially the media achieved low P effluent concentrations of >0.1 mg/L PO4–P, increasing over time. Best P removal was observed for the highest HRT with on average >99%. HRT was seen to be the driving factor for P removal rather than media capacity. Three of the four materials showed pH levels above 12 initially, decreasing over time. Water quality parameters, including organics, solids and metals, were monitored. In-depth analysis confirmed formation of calcium phosphate precipitation on the media's surface. The results suggest the importance of an optimal HRT to achieve high P removal and show that the reactive media application is an appropriate technology for P removal on small sites if the elevated pH is addressed.

Fecal coliform removal in a lightly loaded surface-flow constructed treatment wetland polishing agricultural runoff

2013 ◽  
Vol 68 (4) ◽  
pp. 909-915 ◽  
Author(s):  
Marc W. Beutel ◽  
Victoria Whritenour ◽  
Elaine Brouillard
Keyword(s):  
Retention Time ◽  
Fecal Coliform ◽  
Hydraulic Retention Time ◽  
Agricultural Runoff ◽  
Surface Flow ◽  
Treatment Wetland ◽  
Loss Mechanism ◽  
Sedimentation Basin ◽  
The North ◽  
Loaded Surface

Constructed treatment wetlands can be an effective and sustainable method to remove pathogens that pose health risks from agricultural runoff. This study evaluated the removal of fecal coliform (FC) from agricultural runoff in a lightly loaded surface-flow treatment wetland prior to discharge to the Yakima River, Washington State, USA. The 1.6 ha system consisted of a sedimentation basin (1.4 d hydraulic retention time) followed by two wetlands (5–6 d hydraulic retention time). FC in inflow ranged from 100 to 1,000 cfu/100 mL. Mean annual FC log-removal in the sedimentation basin was 0.66 ± 0.17 (mean plus/minus standard deviation; n = 7). However, there was a comparable production of FC within the two wetlands where annual log-removal averaged −0.71 ± 0.39 in the north wetland and −0.57 ± 0.17 in the south wetland. FC removal in the sedimentation basin weakly correlated with turbidity removal (R2 = 0.13, p < 0.01, n = 61), suggesting that settling was an important FC loss mechanism. FC removal in the wetlands negatively correlated with temperature (R2 = 0.27–0.33, p < 0.01, n = 26) indicating that survival and/or reproduction was an important FC production mechanism. Muskrat colonization in the wetlands in 2007 and 2008 corresponded with a marked increase in FC in wetland outflow. Results suggest that, regardless of the presence of muskrats, sedimentation basins alone are more effective than a combined sedimentation basin–wetland system in removing FC from dilute agricultural runoff.

scholarly journals ANALYSIS OF A WETLAND SYSTEM IN THE POST-TREATMENT OF WASTEWATER

2014 ◽  
Vol 3 (1) ◽  
Author(s):  
Carlos Eduardo Zacarkim ◽  
Luciano Caetano De Oliveira ◽  
Nayara Symanski ◽  
Fernando Rodolfo Espinoza Quinõnes ◽  
Soraya Moreno Palácio ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Retention Time ◽  
Treatment Process ◽  
Hydraulic Retention Time ◽  
Low Cost ◽  
Surface Flow ◽  
Wastewater Treatment Process ◽  
Wetland System ◽  
Simple Technology ◽  
Conventional Systems

The study was based on a surface flow wetland system, using the macrophyte Eicchornia crassipes. The use of wetlands as an alternative in the wastewater treatment process has been employed due to the handling and simple technology, addition to the low cost compared to conventional systems. Three hydraulic retention times, they are 4, 6 and 8 days were analyzed. In general the system showed significant results in relation to removals of nutrients for all TRH reviews, where the hydraulic retention time of 6 days achieved the best performance. The proposed system achieved 79.91% reductions for COD, 83.51% of Total Phosphorus, Total Nitrogen 67.93%, 87.7% chromium and 52% Sulfur.

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