4.4.2 Sizing of the digester
The purpose of this chapter is to practice how to size the digester and what information is required.
| Parameter | Value | Unit | Source |
|---|---|---|---|
| Min Average Temperature during the coldest month | 16.4 | °C | Climate data |
| Retention time | 45 | days | Based on the BMP test at a temperature of 16°C |
| Total inflow rate | 3.72 | m3/day | Calculated in the previous exercise |
| Total organic loading rate | 34 | kgVS/day | Characterisation study |
| Specific organic loading rate for fixed dome digester | 0.75 | kgVS/m3/day | Literature values |
The first step is calculating the necessary hydraulic volume for digestion. This will be determined based on the retention time of 45 days from the BMP test.
Where,
| Parameter | Description | Unit |
|---|---|---|
| VDG | Digester Volume | m³ |
| IN TOTAL | Total Inflow per day | m³/day |
| HRT | Hydraulic Retention time | days |
Before proceeding, we must verify that the digester volume is suitable for the organic loading rate (OLR). If the organic loading rate exceeds the recommended limit of 0.75kgVS per m3 of the digester volume per day, it is advised to expand the volume.
To calculate the organic loading rate per m3 of digester volume per day, we need to divide the total organic loading rate by the digester volume.
Where,
| Parameter | Description | Unit |
|---|---|---|
| OLRS | Specific Organic Loading Rate | kgVS/m³/day |
| OLR | Organic Loading Rate | kgVS/day |
| VDG | Digester Volume | m³ |
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