1.4 Why is Adequate Effluent Management Required?
Effluent from onsite sanitation or after the primary treatment by a faecal sludge treatment plant usually still contains various pollutants, which need to be reduced depending on the application or disposal route.
Let’s explore some of the effluent qualities collected in 2019 in Cox’s Bazar by UPM Umwelt Projekt Management GmbH (UPM) and analysed by UPM or partner laboratories.
| Parameter | Anaerobic Baffled Reactor | Drying Bed (Lime pre-treatment) | Anaerobic Settler and Filter | Dewatering Geobag | Anaerobic Upflow Filter | Biogas Digester | Bangladesh Discharging Standards (ECR-2023 ) | WASH Cluster recommend. for Discharge | Irrigation Standards WHO |
|---|---|---|---|---|---|---|---|---|---|
| Onsite / Offsite | Offsite | Offsite | Onsite | Offsite | Offsite | Onsite | – | – | – |
| Effluent Management | Collected in a pond, and discharged into a stream | Collected in a pond, and discharged into a stream | Discharged into channel | Discharged down the valley. | Soak pit | Collection pit, emptied and treated further | – | – | – |
| Temperature (°C) | 31.9 | 23.2 | 22.2 | 27.6 | ≤ 30 | – | – | ||
| pH | 8.8 | 14 | 8.5 | 8.1 | 8.7 | 7.5 | 6 – 9 | 5 – 9 | – |
| TSS (mg/L) | 500 | 9,500 | 500 | 250 | 219 | 3,625 | ≤ 100 | ≤ 200 | – |
| COD (mg/L) | 400 | 13,600 | 1,875 | 3,850 | 1,275 | 6,780 | ≤125 | ≤ 250 | – |
| BOD5 (mg/L) | 138 | 13,600 | 1,500 | 1,270 | 416 | 2,565 | ≤ 30 | NA | – |
| TN (mg/L) | 623 | 1,890 | 1,274 | 2,692 | 730 | 3,260 | – | ≤ 25 | – |
| NH4-N (mg/L) | 352 | 1,890 | 89 | 1,063 | 30 | 1,075 | – | – | – |
| NO3 (mg/L) | – | – | – | – | – | – | ≤ 50 | – | – |
| TP (mg/L) | 40 | 1,890 | 34 | 12 | 17 | 317 | ≤ 15 | – | – |
| Oil and Grease (mg/L) | – | – | – | – | – | – | ≤ 10 | – | – |
| E.coli / TC (CFU/100mL) | 200,000 | 1,890 | 300,000 | 500,000 | 3,000 | 2,000 | ≤ 1,000 | ≤ 1,000 | ≤ 1,000 |
| Helminths (eggs/L) | nil | 1,890 | 2,000 | 1,000 | 1,000 | 3,000 | – | ≤ 1 | ≤ 1 |
As the table illustrates, the effluent qualities from the different treatment plants do not meet the recommended standards, therefore post-treatment will still be required. The type of post-treatment will depend on the intended effluent management type and the desired quality. For example, agricultural use requires low pathogens to protect human and animal health, but nutrients are beneficial as they are required for plant growth. Suppose the effluent is intended to be discharged into a water body. In that case, the requirements for the post-treatment process are to reduce the nutrients and organics to prevent eutrophication and oxygen depletion as well as the pathogens.
To explore the effluent qualities achieved by faecal sludge treatment plants implemented in Cox’s Bazar, please visit the FSTP Effluent Quality Monitoring Dashboard.
