Table 1. Influent conditions and performance of the studied drinking water treatment plants.
| Compound | Effluent guidelinesa | DWTP1-2b | DWTP3c | DWTP4c | DWTP5c |
|---|---|---|---|---|---|
| Temperature (°C) | — | 9.1±0.4 | 9.5±0.3 | 8.8±0.3 | 9.3±0.4 |
| pH | 7.0–8.5 | 7.4±0.1 | N/A | 7.5±0.1 | 7.4±0.3 |
| Dissolved oxygen (mg O2 l−1) | 5 | 0.26±0.11 | 0.65±0.27 | 0.87±0.44 | 1.09±0.59 |
| Ammonium (mg NH4 l−1) | 0.05 | 1.06±0.18 | 0.51±0.21 | 1.08±0.44 | 0.41±0.2 |
| Iron (mg Fe l−1) | 0.1 | 3.0±0.2 | 2.9±1.7 | 1.9±1.1 | 1.8±1.1 |
| Manganese (mg Mn l−1) | 0.02 | 0.115±0.010 | 0.14±0.09 | 0.07±0.06 | 0.06±0.02 |
| Hydrogen sulfide (mg H2S l−1) | 0.05 | 0.02±0.00 | 0.03±0.02 | 0.12±0.27 | 0.02±0.00 |
| Methane (mg CH4 l−1) | 0.01 | 0.06±0.03 | 0.12±0.17 | 3.73±2.67 | 0.02±0.03 |
| Phosphorus (mg total P l−1) | 0.15 | 0.269±0.051 | N/A | N/A | 0.025±0.01 |
| Bicarbonate (mg HCO3 l−1) | — | 361±6 | N/A | N/A | 346±48 |
| Chloride (mg Cl l−1) | 250 | 55±15 | 51±36 | 41±15 | 64±32 |
| Sulfate(mg SO4 l−1) | 250 | 7±3 | 36±22 | 12±17 | 102±28 |
| NVOC (mg C l−1) | 4 | 2.6±0.3 | 2.7±0.4 | 2.3±0.3 | 2.3±0.3 |
| Treatment plant performance (with regard to guidelines) | — | Problems with incomplete ammonium removal Average effluent NH4 DWTP1: 0.061±0.091 mg NH4 l−1 DWTP2: 0.193±0.245 mg NH4 l−1 (values are averages of 27 measurements from 2010 until 2011)c None of the other above parameters exceeded the effluent guideline from 2009 until 2011b | None of the above parameters exceeded the effluent guideline from 2009 until 2011b (annotation: data only available for combined effluent of DWTP3 and DWTP4) | None of the above parameters exceeded the effluent guideline from 2009 until 2011 (n: 15—except for HCO3−, CH4 and H2S: six measurements)b | |
Abbreviations: DWTP, drinking water treatment plant; N/A, no data available; NVOC, nonvolatile organic carbon.
Raw water values for DWTP5 and DWTP1–2 are weighted averages±s.d. (weighting based on raw water abstraction data). Raw water values for DWTP3 and DWTP4 are average values±s.d.
a
Miljøministeriet (2011). BEK nr 1024 af 31/10/2011: Bekendtgørelse om vandkvalitet og tilsyn med vandforsyningsanlæg—Danish Ministry of the Environment: Ministerial order on water quality and monitoring of water supply systems. Date of publication: 08/11/2011.
b
See Jupiter database (Hansen and Pjetursson, 2011).
c
Water quality raw data obtained from the respective water utilities.