## 1 Introduction
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Parameter** & **Unit** & **Minimum** & **Maximum** & **Average** & **References** \\ \hline Chemical Oxygen & mg/L & 320 & 296,119 & 11,654 & [10; 13; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36] \\ Demand (COD) & mg/L & 125 & 130,000 & 8024 & [10; 20; 24; 25; 26; 32; 34; 36] \\ \hline Biochemical Oxygen & mg/L & 1602 & 79,635 & 11,311 & [20; 34; 37] \\ \hline Total Volatile Solids & mg/L & 130 & 54,952 & 4174 & [19; 20; 24; 34] \\ \hline Suspended Solids & mg/L & 60 & 30,300 & 1435 & [10; 15; 16; 19; 20; 22; 24; 25; 29; 30; 32; 33; 34; 36] \\ \hline pH & - & 3.0 & 12.9 & 5.3 & [13; 14; 15; 16; 19; 22; 24; 25; 27; 28; 30; 32; 33; 34; 32; 35; 36] \\ \hline Total Kjeldahl Nitrogen & mg/L & 0 & 415 & 110 & [20; 24; 28; 34] \\ \hline Total Nitrogen & mg/L & 10 & 415 & 118 & [10; 15; 19; 24; 29; 32; 33; 34; 36; 38] \\ \hline Ammonia Nitrogen & mg/L & 0.001 & 21.1 & - & [10; 29; 36] \\ (N-NH\({}_{3}\)) & mg/L & 3.3 & 188.3 & 39.5 & [10; 19; 20; 24; 25; 29; 33; 34; 36] \\ \hline Phosphorus & mg/L & 7 & 470 & 204 & [14; 20] \\ \hline Potassium & mg/L & 29 & 353 & 201 & [14; 20] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Conventional wastewater pollutants in winery wastewater as reported in literature. Those that do often face high surcharges due to the acidic pH and high COD in the wastewater [6; 13] make onsite treatment an attractive alternative. Historically, onsite treatment of winery wastewater at small wineries has been accomplished by land application [6], but stricter regulations have increased the land that is needed for treatment, reducing that available for vineyards. Currently, activated sludge systems represent the majority of treatment systems at European wineries [6], but they are complex to operate for small wineries and are expensive due to high energy use [7; 9]. Emerging treatment systems for winery wastewater include membrane bioreactors, jet-loop activated sludge, and air micro-bubble reactors, as summarized in [PERSON] et al. (2011) [9]. However, these technologies may not be applicable to small-scale wineries due to their cost, complexity, and limited demonstrated applications [9]. Further, the high variability in strength and volume of winery wastewater is challenging for small-scale wineries that treat their wastewater onsite in order to meet regulations. Northern wine regions, such as Michigan, face the additional challenge of maintaining treatment during cold winter months. For these reasons, it is necessary to develop a low cost, low complexity treatment system that requires less treatment area than traditional land application methods. The treatment system must also be able to handle the high strength and irregular production of winery wastewater, as well as maintain treatment performance during cold weather. Subsurface vertical flow constructed wetlands (SVFCWs) have been previously used to treat diverse, high strength wastewater [45; 46]. In a prior study in our laboratory, SVFCWs were used to biologically treat wastewater in three subsurface gravel cells, where a layer of soil above the SVFCW prevented freezing conditions [47]. An extensive pretreatment system that included a septic tank and an effluent filter mitigated issues that were related to bed clogging [47]. Following pretreatment, wastewater was distributed into the system at the vegetated surface during warm months or below the soil layer during cold months [47]. All of the microbial processes occurred within the lined cells, this preventing metal mobilization. Microbial processes are the main treatment mechanism in SVFCWs, which presents some challenges. During the start-up period of the SVFCW, or after an extended period of no wastewater inflow, nitrogen might not be entirely removed, as nitriving bacteria grow at much slower rates than heterotrophic bacteria [48]. Additionally, it has been shown that vertical flow wetlands do not significantly remove phosphorus [49].