Septage dewatering in vertical-flow constructed wetlands located in the tropics

Constructed wetlands (CWs) have been proven to be an effective low-cost treatment system, which utilizes the interactions of emergent plants and microorganisms in the removal of pollutants. CWs for wastewater treatment are normally designed and operated in horizontal-flow patterns, namely, free-water surface or subsurface flow, while a vertical-flow operation is normally used to treat sludge or septage having high solid contents. In this study, three pilot-scale CW beds, each with a surface area of 25 m2, having 65 cm sand-gravel substrata, supported by ventilated-drainage system and planting with narrow-leave cattails (Typha augustifolia), were fed with septage collected from Bangkok city, Thailand. To operate in a vertical-flow mode, the septage was uniformly distributed on the surface of the CW units. During the first year of operation, the CWs were operated at the solid loading rates (SLR) and application frequencies of, respectively, 80-500 kg total solid (TS)/m2.yr and 1-2 times weekly. It was found that the SLR of 250 kg TS/m2.yr resulted in the highest TS, total chemical oxygen demand (TCOD) and total Kjeldahl nitrogen (TKN) removal of 80, 96 and 92%, respectively. The TS contents of the dewatered septage on the CW beds were increased from 1-2% to 30-60% within an operation cycle. Because of the vertical-flow mode of operation and with the effectiveness of the ventilation pipes, there were high degrees of nitrification occurring in the CW beds. The nitrate (NO3) contents in the CW percolate were 180-250 mg/L, while the raw septage had NO3 contents less than 10 mg/L. Due to rapid flow-through of the percolates, there was little liquid retained in the CW beds, causing the cattail plants to wilt, especially during the dry season. To reduce the wilting effects, the operating strategies in the second year were modified by ponding the percolate in the CW beds for periods of 2 and 6 days prior to discharge. This operating strategy was found beneficial not only for mitigating plant wilting, but also for increasing N removal through enhanced denitrification activities in the CW beds. During these 2 year operations, the dewatered septage was not removed from the CW beds and no adverse effects on the septage dewatering efficiency were observed.

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Treatment performances of French constructed wetlands: results from a database collected over the last 30 years

Water Science & Technology ◽

10.2166/wst.2015.089 ◽

2015 ◽

Vol 71 (9) ◽

pp. 1333-1339 ◽

Cited By ~ 30

Author(s):

A. Morvannou ◽

N. Forquet ◽

S. Michel ◽

S. Troesch ◽

P. Molle

Keyword(s):

Constructed Wetlands ◽

Oxygen Demand ◽

Pollutant Removal ◽

Vertical Flow ◽

Removal Rates ◽

Waste Stabilization Ponds ◽

Small Communities ◽

Technical Department ◽

In Series ◽

High Chemical Oxygen Demand

Approximately 3,500 constructed wetlands (CWs) provide raw wastewater treatment in France for small communities (<5,000 people equivalent). Built during the past 30 years, most consist of two vertical flow constructed wetlands (VFCWs) in series (stages). Many configurations exist, with systems associated with horizontal flow filters or waste stabilization ponds, vertical flow with recirculation, partially saturated systems, etc. A database analyzed 10 years earlier on the classical French system summarized the global performances data. This paper provides a similar analysis of performance data from 415 full-scale two-stage VFCWs from an improved database expanded by monitoring data available from Irstea and the French technical department. Trends presented in the first study are confirmed, exhibiting high chemical oxygen demand (COD), total suspended solids (TSS) and total Kjeldahl nitrogen (TKN) removal rates (87%, 93% and 84%, respectively). Typical concentrations at the second-stage outlet are 74 mgCOD L−1, 17 mgTSS L−1 and 11 mgTKN L−1. Pollutant removal performances are summarized in relation to the loads applied at the first treatment stage. While COD and TSS removal rates remain stable over the range of applied loads, the spreading of TKN removal rates increases as applied loads increase.

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Using one filter stage of unsaturated/saturated vertical flow filters for nitrogen removal and footprint reduction of constructed wetlands

Water Science & Technology ◽

10.2166/wst.2017.115 ◽

2017 ◽

Vol 76 (1) ◽

pp. 124-133 ◽

Cited By ~ 4

Author(s):

Ania Morvannou ◽

Stéphane Troesch ◽

Dirk Esser ◽

Nicolas Forquet ◽

Alain Petitjean ◽

...

Keyword(s):

Constructed Wetlands ◽

Oxygen Demand ◽

Pollutant Removal ◽

Operating Conditions ◽

Vertical Flow ◽

Saturated Layer ◽

Recirculation Rate ◽

Total Filtration ◽

Filtration Area ◽

Stage System

French vertical flow constructed wetlands (VFCW) treating raw wastewater have been developed successfully over the last 30 years. Nevertheless, the two-stage VFCWs require a total filtration area of 2–2.5 m2/P.E. Therefore, implementing a one-stage system in which treatment performances reach standard requirements is of interest. Biho-Filter® is one of the solutions developed in France by Epur Nature. Biho-Filter® is a vertical flow system with an unsaturated layer at the top and a saturated layer at the bottom. The aim of this study was to assess this new configuration and to optimize its design and operating conditions. The hydraulic functioning and pollutant removal efficiency of three different Biho-Filter® plants commissioned between 2011 and 2012 were studied. Outlet concentrations of the most efficient Biho-Filter® configuration are 70 mg/L, 15 mg/L, 15 mg/L and 25 mg/L for chemical oxygen demand (COD), 5-day biological oxygen demand (BOD5), total suspended solids (TSS) and total Kjeldahl nitrogen (TKN), respectively. Up to 60% of total nitrogen is removed. Nitrification efficiency is mainly influenced by the height of the unsaturated zone and the recirculation rate. The optimum recirculation rate was found to be 100%. Denitrification in the saturated zone works at best with an influent COD/NO3-N ratio at the inflet of this zone larger than 2 and a hydraulic retention time longer than 0.75 days.

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Nitrogen removal in a combined system: vertical vegetated bed over horizontal flow sand bed

Water Science & Technology ◽

10.2166/wst.2001.0820 ◽

2001 ◽

Vol 44 (11-12) ◽

pp. 137-142 ◽

Cited By ~ 25

Author(s):

S. Kantawanichkul ◽

P. Neamkam ◽

R.B.E. Shutes

Keyword(s):

Loading Rate ◽

Low Cost ◽

Oxygen Demand ◽

Nitrogen Loading ◽

Horizontal Flow ◽

Vertical Flow ◽

Combined System ◽

Cost Treatment ◽

Pig Farm ◽

Farm Wastewater

Pig farm wastewater creates various problems in many areas throughout Thailand. Constructed wetland systems are an appropriate, low cost treatment option for tropical countries such as Thailand. In this study, a combined system (a vertical flow bed planted with Cyperus flabelliformis over a horizontal flow sand bed without plants) was used to treat settled pig farm wastewater . This system is suitable for using in farms where land is limited. The average COD and nitrogen loading rate of the vegetated vertical flow bed were 105 g/m2.d and 11 g/m2.d respectively. The wastewater was fed intermittently at intervals of 4 hours with a hydraulic loading rate of 3.7 cm/d. The recirculation of the effluent increased total nitrogen (TN) removal efficiency from 71% to 85%. The chemical oxygen demand (COD) and total Kjeldahl nitrogen (TKN) removal efficiencies were 95% and 98%. Nitrification was significant in vertical flow Cyperus bed, and the concentration of nitrate increased by a factor of 140. The horizontal flow sand bed enhanced COD removal and nitrate reduction was 60%. Plant uptake of nitrogen was 1.1 g N/m2.d or dry biomass production was 2.8 kg/m2 over 100 days.

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Effects of selection and compiling strategy of substrates in column-type vertical-flow constructed wetlands on the treatment of synthetic landfill leachate containing bisphenol A

Water Science & Technology ◽

10.2166/wst.2021.349 ◽

2021 ◽

Author(s):

Rajani Ghaju Shrestha ◽

Daisuke Inoue ◽

Michihiko Ike

Keyword(s):

Activated Carbon ◽

Bisphenol A ◽

Landfill Leachate ◽

Low Cost ◽

Oxygen Demand ◽

Ammonium Nitrogen ◽

Pollutant Removal ◽

Vertical Flow ◽

Batch Mode ◽

Synthetic Leachate

Abstract A constructed wetland (CW) is a low-cost, eco-friendly, easy-to-maintain, and widely applicable technology for treating various pollutants in the waste landfill leachate. This study determined the effects of the selection and compiling strategy of substrates used in CWs on the treatment performance of a synthetic leachate containing bisphenol A (BPA) as a representative recalcitrant pollutant. We operated five types of lab-scale vertical-flow CWs using only gravel (CW1), a sandwich of gravel with activated carbon (CW2) or brick crumbs (CW3), and two-stage hybrid CWs using gravel in one column and activated carbon (CW4) or brick crumbs (CW5) in another to treat synthetic leachate containing BPA in a 7-d sequential batch mode for 5 weeks. CWs using activated carbon (CW2 and CW4) effectively removed ammonium nitrogen (NH4-N) (99–100%), chemical oxygen demand (COD) (93–100%), and BPA (100%), indicating that the high adsorption capacity of activated carbon was the main mechanism involved in their removal. CW5 also exhibited higher pollutant removal efficiencies (NH4-N: 94–99%, COD: 89–98%, BPA: 89–100%) than single-column CWs (CW1 and CW3) (NH4-N: 76–100%, COD: 84–100%, BPA: 51–100%). This indicates the importance of the compiling strategy along with the selection of an appropriate substrate to improve the pollutant removal capability of CWs.

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Constructed Wetlands in Latin America and the Caribbean: A Review of Experiences during the Last Decade

Water ◽

10.3390/w12061744 ◽

2020 ◽

Vol 12 (6) ◽

pp. 1744

Author(s):

Marco A. Rodriguez-Dominguez ◽

Dennis Konnerup ◽

Hans Brix ◽

Carlos A. Arias

Keyword(s):

Latin America ◽

Plant Species ◽

Constructed Wetlands ◽

Oxygen Demand ◽

Free Water ◽

Sufficient Information ◽

Local Conditions ◽

Latin America And Caribbean ◽

The Mean ◽

Low Performance

The review aims to report the state-of-the-art constructed wetlands (CW) in the Latin America and Caribbean (LAC) region not limited to national and local conditions. The aim is with a broader view, to bring updated and sufficient information, to facilitate the use of the CW technology in the different countries of LAC. Thus, 520 experiences extracted from the 169 reviewed documents in 20 countries were analyzed. According to the data, horizontal subsurface flow wetlands are the most reported CW in the region (62%), the second most common CW technology in the region is free water surface CW (17%), then vertical flow systems (9%), followed by intensified constructed wetlands (8%), and finally French systems (4%). The performance for nutrient removal is analyzed, finding that the mean of Chemical Oxygen Demand (COD), Total Nitrogen (TN), and Total Phosphorous (TP) removal efficiencies varies from 65% to 83%, 55% to 72%, and 30% to 84%, respectively. The results suggest a generally good performance for COD and TN removal, but a low performance for TP removal. Regarding plant species used for CWs, 114 different plant species were reported, being until now the most extensive report about plant species used in CWs in the LAC region.

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Performance of a French system of vertical flow wetlands (first stage) operating with an extended feeding cycle

Water Science & Technology ◽

10.2166/wst.2019.395 ◽

2019 ◽

Vol 80 (8) ◽

pp. 1443-1455 ◽

Cited By ~ 1

Author(s):

Camila Maria Trein ◽

Jorge Alejandro García Zumalacarregui ◽

Mirene Augusta de Andrade Moraes ◽

Marcos von Sperling

Keyword(s):

Oxygen Demand ◽

Climatic Conditions ◽

Nitrification Rate ◽

Vertical Flow ◽

Intensive Monitoring ◽

The Third ◽

Treatment Performance ◽

N Removal ◽

Feeding Cycle ◽

Deposit Layer

Abstract The aim of this work was to evaluate the treatment performance in the first stage of a vertical flow constructed wetland – French system (VCW-FS) over an extended feeding period (seven days), in two parallel units, for a population equivalent (p.e.) around 100 inhabitants (total of 0.6 m²·p.e.−1), under Brazilian tropical climatic conditions. One of the units had a greater surface sludge deposit layer, accumulated over nine years of operation, while the other unit had its sludge removed prior to the experiments. Four intensive monitoring campaigns covering all days of the feeding cycle were undertaken and the results were compared with those obtained from the conventional monitoring. The results indicated that, over the days of the feeding cycle, dissolved oxygen concentrations decreased, but were still kept at sufficiently high values for the removal of organic matter. Therefore, chemical oxygen demand (COD) removal, although not high, remained acceptable for compliance with local discharge standards during the whole the period. The NH4+-N removal efficiency and NO3−-N production were higher at the beginning of the feeding cycle, as a result of the more well-established aerobic conditions, with the nitrification rate decreasing from the third day of feeding. The sludge deposit seemed to hinder liquid percolation, especially at the end of the feeding cycle, thus affecting oxygen transfer. Due to the variability of the results over the feeding cycle, if sampling is to be done once a week, it is important to identify the sampling day that best represents the system's performance.

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Removal of Levafix Red from Aqueous Solution with Treated Jute Stick and its Relevance to Pharmaceutical Field

Bangladesh Pharmaceutical Journal ◽

10.3329/bpj.v19i1.29242 ◽

2016 ◽

Vol 19 (1) ◽

pp. 75-84

Author(s):

Rayhan Hossain ◽

Mohammad Arifur Rahman ◽

Nargish Jahan Ara ◽

AM Shafiqul Alam

Keyword(s):

Waste Water ◽

Low Cost ◽

Animal Health ◽

Oxygen Demand ◽

Free Water ◽

Second Order ◽

Batch Adsorption ◽

High Concentration ◽

Pseudo Second Order ◽

Pharmaceutical Industries

The adsorption of levafix red (LR) dye from waste water via batch adsorption onto treated jute stick powder was investigated. Studies concerning the factors influencing the adsorption such as adsorbent dosage, pH, contact time and temperature were systematically investigated and discussed. The results revealed that the maximum removal of levafix red was ~91% from water. The kinetics data were analyzed using pseudo-first order and pseudo-second order models. It was best described by the pseudo-second order model. The adsorption equilibrium follows Langmuir isotherm. This result indicates that treated jute stick powder could be employed as low-cost alternatives to commercial activated carbon for the removal of levafix red (LR) from waste water. Rapid industrialization in Bangladesh has resulted in increased water pollution that has higher dye level. Waste water from dyeing and finishing factories is a significant source of environmental pollution. The waste water is typically characterized by high levels of COD (chemical oxygen demand) concentration, high concentration of coloring material, large amount of suspended solids, highly fluctuating pH and high temperature. Dyes may therefore present an ecotoxic hazard and introduces the potential danger of bioaccumulation that may eventually affect man by transport through the food chain. As pharmaceutical industries use lots of water and intake of this type of water might have adverse effects on human health. Therefore, water purification is extremely essential for human and animal health and dye free water may be farther purified for its proper use.Bangladesh Pharmaceutical Journal 19(1): 75-84, 2016

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Effect of corn cobs as external carbon sources on nitrogen removal in constructed wetlands treating micro-polluted river water

Water Science & Technology ◽

10.2166/wst.2019.156 ◽

2019 ◽

Vol 79 (9) ◽

pp. 1639-1647 ◽

Cited By ~ 2

Author(s):

Lu-ji Yu ◽

Tao Chen ◽

Yanhong Xu

Keyword(s):

Organic Carbon ◽

River Water ◽

Constructed Wetlands ◽

Carbon Sources ◽

Oxygen Demand ◽

Ammonia Nitrogen ◽

Flow Mode ◽

Low Carbon ◽

Polluted River ◽

Corn Cobs

Abstract Micro-polluted river water is characterized as having limited biodegradability, low carbon to nitrogen ratio and little organic carbon supply, all of which makes it hard to further purify. Two bench scale constructed wetlands (CWs) with a horizontal subsurface flow mode were set up in the laboratory to evaluate their feasibility and efficiency on denitrification with and without corn cobs as external carbon sources. Micro-polluted river water was used as feed solution. The CW without corn cobs substrates possessed a good performance in removing chemical oxygen demand (COD, <40 mg/L) and ammonia nitrogen (NH3-N, <0.65 mg/L), but less efficiency in removing total nitrogen (TN) and nitrate nitrogen (NO3-N). In marked contrast, the CW with 1% (w/w) corn cobs substrates as external carbon sources achieved a significant improvement in the removal efficiency of TN (increased from 34.2% to 71.9%) and NO3-N (increased from 19% to 71.9%). The incorporation of corn cobs substrates did not cause any obvious increase in the concentrations of COD and NH3-N in the effluent. This improvement in the denitrification efficiency was owing to the released organic carbon from corn cobs substrates, which facilitated the growth of abundant microbes on the surface and pores of the substrate. The open area of the used corn chips is larger than that of the pristine ones, and corn cobs can continue to provide a carbon fiber source for denitrification.

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Design Recommendations for Subsurface Flow Constructed Wetlands for Nitrification and Denitrification

Water Science & Technology ◽

10.2166/wst.1999.0170 ◽

1999 ◽

Vol 40 (3) ◽

pp. 257-263 ◽

Cited By ~ 40

Author(s):

Christoph Platzer

Keyword(s):

Wastewater Treatment ◽

Constructed Wetlands ◽

Wastewater Treatment Plants ◽

Subsurface Flow ◽

Oxygen Demand ◽

Oxygen Balance ◽

Vertical Flow ◽

Soil Aeration ◽

Return Rates ◽

Nitrification And Denitrification

The paper presents a design for nitrogen removal in subsurface flow wetlands. The nitrification in the vertical-flow beds (VFBs) is clearly determined by the oxygen balance in the filter. Full nitrification can only be achieved when the oxygen balance is positive. For sizing purposes equations for the calculation of oxygen demand and oxygen input are given. Three possibilities to achieve sufficient soil aeration are presented and explained. For the denitrification two possibilities are presented. From technical wastewater treatment plants predenitrification is well known. Return rates up to 200% can be used without hydraulic problems for the VFBs. In cases of low C/N ratios an additional application of HFBs has to be used. The design can be carried out using a design of 1 g NO3-N/m2,d achieving a 65% removal in more than 90% of the cases. The paper discusses some of the equations presented internationally. The suitability of the use of k-values for the processes nitrification and denitrification is especially questioned.

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Vertical-flow constructed wetlands treating domestic wastewater contaminated by hydrocarbons

Water Science & Technology ◽

10.2166/wst.2015.054 ◽

2015 ◽

Vol 71 (6) ◽

pp. 938-946 ◽

Cited By ~ 5

Author(s):

R. H. K. Al-Isawi ◽

A. Sani ◽

S. A. A. A. N. Almuktar ◽

M. Scholz

Keyword(s):

Positive Impact ◽

Oxygen Demand ◽

Aggregate Size ◽

Ammonia Nitrogen ◽

Flow Mode ◽

Vertical Flow ◽

Treatment Standards ◽

Diesel Spill ◽

The Impact ◽

Outflow Concentration

The aim was to compare the impact of different design (aggregate size) and operational (contact time, empty time and chemical oxygen demand (COD) loading) variables on the long-term and seasonal performance of vertical-flow constructed wetland filters operated in tidal flow mode before and after a one-off spill of diesel. Ten different vertical-flow wetland systems were planted with Phragmites australis (Cav.) Trin. ex Steud. (common reed). Approximately 130 g of diesel fuel was poured into four wetland filters. Before the spill, compliance with secondary wastewater treatment standards was achieved by all wetlands regarding ammonia-nitrogen (NH4-N), nitrate-nitrogen (NO3-N) and suspended solids (SS), and non-compliance was recorded for biochemical oxygen demand and ortho-phosphate-phosphorus (PO4-P). Higher COD inflow concentrations had a significantly positive impact on the treatment performance for COD, PO4-P and SS. The wetland with the largest aggregate size had the lowest mean NO3-N outflow concentration. However, the results were similar regardless of aggregate size and resting time for most variables. Clear seasonal outflow concentration trends were recorded for COD, NH4-N and NO3-N. No filter clogging was observed. The removal efficiencies dropped for those filters impacted by the diesel spill. The wetlands system shows a good performance regarding total petroleum hydrocarbon (TPH) removal.

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