# High Rate Stormwater Treatment for Water Reuse and Conservation--Review
## 5 High-Rate Stormwater Treatment Technologies
### Applications of High-Rate Filter Systems  
High-rate treatment systems present a sustainable solution for urban development by reducing the need for municipal water, lessening pollutants in stormwater, and minimizing the release of stormwater. The byproducts generated from these treatment processes (concentrated pollutants, sludge), are usually routed to the sewer system, helping to solve sludge disposal issues and offering a low-maintenance option. Utilizing water reuse systems like these can effectively reduce the transport of stormwater contaminants from locations to adjacent water bodies. Table 8 highlights the efficiency of high-rate treatment systems used for stormwater reuse. These systems demonstrate impressive removal rates for physical pollutants (suspended solids, turbidity), heavy metals (including Fe, Mn, and Pb), as well as organic matter. Their small design footprint allows for minimal land use, as there is no need for water storage prior to pre-treatment. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**High Rate System** & **Fiber Filter 1** & **Deep Bed Filter 1** & **Submerged Membrane Hybrid Systems** & **GAC Biofilter** \\ \hline Heavy Metals & 90\% & 40–54\% & - 2 & 90\% \\ Total Phosphorus & 90\% & 50\% & - 2 & 74\% \\ Total Nitrogen & 90\% & 38\% & - 2 & 34\% \\ Turbidity 3 & 95\% & 95\% & 98\% & 75\% \\ TOC & 40\% & 30–45\% & 40\% & 100\% \\ _E. coli_3 & 93\% & 80\% & 99.9\% & - \\ \hline \hline \end{tabular}  
* in conjunction with in-line flocculent ferric chloride addition 2 at least equal to fiber filter, deep bed filter, or biofilter depending on the system the membrane filter is coupled to. Usually, membrane systems are coupled with in-line flocculent or adsorbent addition. 3 influent and effluent pollutant concentrations in mg/L except for turbidity (NTU) and _E. coli_ (fcu/100 mL).  
\end{table} 
Table 7: Indicative percentage of pollution retained in the treatment system and indicative levels of pollutants in the outflow for a range of high-rate treatment measures (modified from [PERSON] et al. [52]). Materials and Methods on high-rate systems: A detailed on-site pilot-filtration study was conducted in Kogarah, Sydney, Australia to evaluate the performance of filters using anthracite coal and granular activated carbon (GAC) at high filtration velocities for the removal of solids, heavy metals, and organic pollutants (Figure 2). Raw harvesting water was stored in a tank (Figure 2). Samples of raw water were sourced from a stormwater harvesting facility in Sydney, Australia. The stormwater primarily came from base flow, which continuously moves through the canal during dry spells. A pit located at the base of the canal allowed stormwater to drain by gravity to a nearby wet well. From there, it was pumped through to a control valve pit where turbidity levels are monitored. Should the turbidity exceed 50 NTU, the stormwater is diverted to a return pit leading back to the canal; otherwise, it continues to the filtration plant at a flow rate of 0.7 L/s (2.5 kL/h)  
Raw water from the tank was pumped to the filter column which was operated in downflow mode. Two filter set-ups were used. In the first setup (Figure 2a) GAC media filter was operated alone. The characteristics of GAC are given in the Supporting Information Table S1. In the second (Figure 2b) a prefilter column packed with anthracite followed by a GAC filter was used. The columns had a medium height of 1 m and were operated at a flow rate of 10 m/h. Samples were taken at the outlet tap to each filter column. They were operated continuously for 4 h each day over a period of three days. At the  
Figure 2: GAC media filter (**a**) without and (**b**) with prefilter packed with anthracite (filtration rate = 10 m/h, filter media height = 1 m, filter column height = 18 m, filter diameter = 0.1 m).