Peat/sand filter technology is designed and engineered for in-ground application to manage "first flush" runoff. The design typically employs a top layer of peat/soil, a layer of sand, and then a bottom layer of gravel to optimize drainage. Originally designed as a wastewater treatment technology, this is effective for stormwater treatment as well. Nutrient removal performance actually increases with increasing pollutant concentrations, although it is not uncommon for negative performance to be initially observed until microbial and planted communities are established. The average performance is as shown below. Note that with all stormwater treatment technologies, there are instances of failure and limitations to what can be achieved.*
Peat/Sand Filters Performance*
| Pollutant | Sand Filters | Peat-sand Filters |
| TSS | 60-80% | 80-100% |
| TP | 20-40% | 60-80% |
| TN | 20-40% | 40-60% |
| BOD | 60-80% | 80-100% |
| Metals | 40-60% | 40-60% |
| Bacteria | 60-80% | 80-100% |
One may notice that the performance is much improved with the addition of peat to a simple sand filter. This may be relevant if a simple sand technology is being considered, as peat is an economical means to substantially improve system performance. Maintenance is fairly simple, that of grass cutting.* However, as a note, cut grass will return acquired nutrients back to the soil.
This range of performance is broader than shown by the EPA data but perhaps may more accurately reflect variations is performance.
*Debo, Thomas N., and Reese, Andrew, J. 1995. Municipal Storm Water Management. Lewis Publishers, ISBN: 0873719816