Applicability of Constructed Wetlands for Water Quality Improvement in a Tea Estate Catchment: The Pussellawa Case Study

Abstract

Abstract:Water in agricultural catchments is prone to pollution from agricultural runoff containing nutrients and pesticides, and contamination from the human population working and residing therein. This study examined the quality of water in a drainage stream which runs through a congested network of 'line houses' (low-income housing, typically found arranged in straight 'lines' on estates) in the tea estate catchment area of Pussellawa in central Sri Lanka. The study evaluated the applicability of vertical subsurface flow (VSSF) and horizontal subsurface flow (HSSF) constructed wetlands for water polishing, as the residents use the stream water for various domestic purposes with no treatment other than possibly boiling. Water flow in the stream can vary significantly over time, and so investigations were conducted at various flow conditions to identify the hydraulic loading rate (HLR) bandwidth for wetland polishing applications. Two wetland models of 8 m × 1 m × 0.6 m (length × width × depth) were constructed and arranged as VSSF and HSSF units. Stream water was diverted to these units at HLRs of 3.3, 4, 5, 10, 20, and 40 cm/day. Results showed that both VSSF and HSSF wetland units were capable of substantially reducing five-day biochemical oxygen demand (BOD 5 ), total suspended solids (TSS), fecal coliform (FC), total coliform (TC), ammonia nitrogen (NH 4 + -N), and nitrate nitrogen (NO 3 − -N) up to 20 cm/day HLR, with removal efficiencies of more than 64%, 60%, 90%, 93%, 70%, and 59% for BOD 5 , TSS, FC, TC, NH 4 + -N, and NO 3 − -N, respectively, in the VSSF wetland unit; and more than 66%, 62%, 91%, 90%, 53%, and 77% for BOD 5 , TSS, FC, TC, NH 4 + -N, and NO 3 − -N, respectively, in the HSSF wetland unit.

A Literature Review of Wetland Treatment Systems Used to Treat Runoff Mixtures Containing Antibiotics and Pesticides from Urban and Agricultural Landscapes

“…It is important to note that not all studies used wetland plants [43,83,89] or identified the specific plant species within the wetland system [148,159,179]. Also, not all primary studies that specified the plant species present in the wetland system analyzed the impact of phytoremediation as a removal mechanism [21,173,205]. For the studies that did investigate phytoremediation, vegetated systems increased removal efficiencies compared to non-vegetated systems [51,55,66,95,154,161,175,181,217], with mature plants out-performing younger ones [158].…”

“…Wetland treatment systems, including natural and constructed wetlands, are now being used extensively across the United States and the world to treat non-point source pollution. This is due to their cost-effectiveness and low energy consumption compared to other surface water treatment methods (e.g., coagulation, membrane filtration, ion exchange) [20][21][22]. Wetlands utilize plants, soils, and associated microbial assemblages to remove pollutants through biodegradation, substrate adsorption, and plant uptake [23,24].…”

Feasibility of Constructed Wetland Using Coagulation Flocculation Technology in Batik Wastewater Treatment

“…The TSS removal process in HSSFCW is due to the deposition process caused by the interception of suspended solids because of the reduced speed of water flow through wetland media Vymazal et al, 1998; Wallace and Knight, 2006;Weerakoon et al, 2018). In fine-grained media, the interception process occurs randomly either at the micro scale (Brownian motion) or macro scale (bioturbation) which makes it easy for the particles to settle (Kadlec and Wallace, 2009;Vymazal et al, 1998).…”

Effectiveness of two-stage horizontal subsurface flow constructed wetland planted with Cyperus alternifolius and Typha latifolia in treating anaerobic reactor brewery effluent at different hydraulic residence times

“…The efficiency of the series-connected two-stage HSS-FCW treatment system showed a variable removal efficiency of TSS and COD, despite the significant influent fluctuations. Other studies also reported that the degradation and sedimentation of pollutants in the HSSFCW treatment system are mostly affected by hydraulic factors (i.e., HRT or HLR) and mass loading rate (Ghosh and Gopal 2010;Jinadasa et al 2013;Shuib and Baskaran 2015). Furthermore, the treatment efficiency of a HSSFCW system is dependent on the nature of the original wastewater supply, selection of media types, feeding mode, and aeration conditions (Stefanakis and Tsihrintzis, 2012).…”

“…Many authors have also recommend that the UASB-CW integrated treatment system has a high potential to improve water quality (Badejo et al 2014;Raboni et al 2014), since the UASB reactor removes most of the organic matter (Morino-Solis et al 2015), reduces the large wetland area requirement (Alvarez et al 2008), avoids wetland clogging problems, and increases the life cycle of CW (Kyambadde et al 2005). While the CW further mitigates the remaining organics, solids, nutrients, and pathogens (Balleseros et al 2016;Jinadasa et al 2013), and heavy metals (Sedaqua 2013). Moreover, the application of this integrated treatment technology is promising for resource-limited countries due to its superior advantages mentioned elsewhere (Jamashidi et al 2014;Kyambadde et al 2005).…”