Abstract
The anaerobic process is considered to be a sustainable technology for the treatment of wastewaters rich in organic matter mainly due to its lower energy consumption and production of value-added products such as biogas and organic fertilizer. However, it cannot be seen as providing ‘complete’ environmental solution as its treated effluents would typically not meet the desired discharge limits in terms of residual carbon, nutrients and other pollutants. This has given impetus to subsequent post treatment in order to meet the environmental standards and protect the receiving water bodies and environment. The aim of this study was to evaluate the post-treatment potential of a pilot scale two-stage horizontal subsurface flow constructed wetland (HSSFCW) system planted with Cyperus alternifolius and Typha latifolia, respectively, for enhanced removal of residual carbon and nutrient from an up-flow anaerobic sludge blanket (UASB) reactor treated brewery effluent. A pilot scale two-stage HSSFCW was integrated with the UASB reactor, and its performance efficiency was assessed for the removal of total suspended solids (TSS), chemical oxygen demand (COD), total nitrogen (TN), ammonium–nitrogen (NH4–N), total phosphorous (TP), and orthophosphate (PO43−). Macrophytes aboveground biomass and nutrient accumulation potential were also determined following standard methods. The results from this study showed that Cyperus alternifolius planted CW cell removed 68.5% TSS, 74.2% COD, 55.7% TN, 68.6% NH4–N, 41.1% TP and 48.1% PO43−. Moreover, further polishing with Typha latifolia planted CW cell enhanced the removal efficiencies to 89% TSS, 92% COD, 83.6% TN, 92.9% NH4–N, 74.4% TP, and 79.5% PO43−. Strong linearity and Pearson correlation was found between macrophyte biomass and nutrient accumulation in each CW cell (Cyperus alternifolius: R2 = 0.91, r = 0.97 for TN; R2 = 0.92, r = 0.96 for TP; and Typha latifolia: R2 = 0.96, r = 0.98 for TN and TP), and showed substantial nutrient reduction with cumulative nutrient accumulation of 1290 gTNm−2 and 708.7 gTPm−2 in the complete system. The performance of the pilot CW system as a tertiary treatment for brewery wastewater showed that the effluent meets the permissible discharge standards throughout the year excluding phosphorous.
Highlights
In developing countries, only 8% of wastewater is treated, and reckless disposal of untreated municipal and agroprocessing industrial wastes laden with organic matter, nutrients, and other hazardous chemicals into water bodies and the environment poses ecological and health risks (Nebyou 2011; Worku et al 2018; Ashekuzzaman et al 2020)
To generate empirical information to the operational condition of constructed wetlands (CW), we developed a series connected twostage horizontal subsurface flow constructed wetland (HSSFCW) system, one planted with C. alternifolius and another planted with T. latifolia, for the enhanced removal of organics and nutrients from anaerobically treated brewery effluent
Experimental location Wetland surface area (As) horizontal subsurface flow constructed wetland (HSSFCW) pilot plant was built on the premises of Kombolcha Brewery connected with the existing an up-flow anaerobic sludge blanket (UASB) treatment plant in Kombolcha town, Northern Ethiopia, located at 11°04 ́42.43 ́ ́N 39°43 ́34.45 ́ ́ E and 1833 m above sea level, an area with annual average minimum and maximum temperatures varying between 6.1–15.2 °C and 24.7–30.4 °C, respectively, and mean annual rainfall of 255.7 mm
Summary
Only 8% of wastewater is treated, and reckless disposal of untreated municipal and agroprocessing industrial wastes laden with organic matter, nutrients, and other hazardous chemicals into water bodies and the environment poses ecological and health risks (Nebyou 2011; Worku et al 2018; Ashekuzzaman et al 2020). In Ethiopia, most of the breweries drain their effluents into rivers and nearby environment, and cause water bodies to stench, discoloration, and oily nature (Belay and Sahile 2013), while effluents used for irrigation can pose soil pollution problem (Oljira et al 2018). To reduce these problems, environmental authorities are pressuring the breweries to manage their effluents below environmental standards. Even though several other alternative polishing options are available, naturally working constructed wetlands (CW) are gained popularity as an ecofriendly polishing technology, and recently utilized for different anaerobic reactor effluent treatment (Zeb et al 2013; Jamshidi et al 2014)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
