Effect of hydraulic retention time, temperature, and organic load on a horizontal subsurface flow constructed wetland treating cheese whey wastewater

Abstract

BACKGROUND One of the main components of dairy wastewaters is cheese whey. Although different technologies have been used extensively in the past for cheese‐whey treatment, constructed wetlands (CWs) applications are limited. Furthermore, the effect of crucial operational parameters (e.g. temperature, pollutant loading rate) have not been thoroughly studied. Having this in mind, two horizontal subsurface flow pilot‐scale CW units (one planted and one unplanted) were used to treat secondary cheese whey, in order to examine the effect of different chemical oxygen demand (COD) influent concentrations (1200 to 7200 mg L−1), hydraulic residence times (8, 4, 2 and 1 day) and temperature (2.4 to 32.9 °C). RESULTS During a 2‐year operating period both pilot‐scale units successfully removed organic matter, with COD removal efficiencies recorded at 91% and 77.2% for the planted and the unplanted unit, respectively. Hydraulic residence time affected COD removal efficiency only when limited to 1 day. Temperature significantly affected COD removal only in the unplanted unit. CONCLUSIONS Constructed wetlands could successfully treat secondary cheese whey and provide COD effluent concentrations below EU legislation, when hydraulic residence time is above 2 days and COD influent concentration ranges from 1200 to 3500 mg L−1. © 2015 Society of Chemical Industry

Refining of wine lees and cheese whey for the production of microbial oil, polyphenol‐rich extracts and value‐added co‐products

“…The worldwide annual production capacity of cheese whey could be estimated at about 160 million t . Cheese whey retains most of the milk lactose (39–60 g L −1 ) as well as proteins (1.4–33.5 g L −1 ), fats (0.99–10.58 g L −1 ), and mineral salts (0.46–10%) among others .…”

Treatment of second cheese whey effluents using aChoricystis-based system with simultaneous lipid production

“…Consequently, a suitable post‐treatment step should be applied to improve the quality of the final discharge in terms of residual pollutant content. This post‐treatment could include a second aerobic biological filter or a constructed wetland …”

Treatment of table olive washing water using trickling filters, constructed wetlands and electrooxidation

“…On the contrary, no significant differences (p = 0.376 for OG-P and 0.073 for OG-U) were recorded for HRTs of 4 and 8 days (90 % for OG-P and 78 % OG-U). As reported by Sultana et al (2016), an HRT of 4 days is sufficient to safely remove organic matter when COD influent concentrations are below 2500 mg/L. COD removal is temperature dependent thus implying that organic matter removal is mostly a result of aerobic and anaerobic bacterial activity (Akratos and Tsihrintzis, 2007), as bacteria increase their function when air temperature rises.…”

“…Three different HRTs that have been previously used for organic matter removal in HSF constructed wetlands (i.e. 2, 4 and 8 days) were applied in the present study (Sultana et al, 2016;Akratos and Tsihrintzis, 2007). The effect of HRT on COD removal was assessed by performing one-way ANOVA analysis in specific data sets, where temperature values were not significantly different (p = 0.007 > 0.05) and COD influent concentrations were almost identical.…”

“…COD removal is temperature dependent thus implying that organic matter removal is mostly a result of aerobic and anaerobic bacterial activity (Akratos and Tsihrintzis, 2007), as bacteria increase their function when air temperature rises. To statistically assess the effect of temperature on COD removal, the results obtained from experiments conducted with an HRT of 4 days were divided into two data sets (above and below 15°C) (Sultana et al, 2016;Akratos and Tsihrintzis, 2007). While temperature did not significantly affect the unplanted unit (OG-U) (p = 0.678), the planted unit (OG-P) was significantly affected by temperature (p = 0.026).…”