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Quality of pre-treated AD effluent and its difference between each batch_ Data are shown in (mg L-1)_
| May | June | July | August | |
|---|---|---|---|---|
| pH | 7.62 | 7.39 | 8.15 | 8.06 |
| COD | 615 | 1597 | 750 | 667 |
| TSS | 30 | 140 | 150 | 65 |
| total-P | 97 | 100 | 61 | 75 |
| dissolved-P | 68 | 56 | 58 | 36 |
| N(NH4-NH3+) | 683 | 622 | 930 | 872 |
| organic-N | 8 | 8 | 53 | 67 |
| nitrite-N | 0.010 | 0.036 | 0.041 | 0.023 |
| nitrate-N | 6.200 | 1.300 | 0.152 | 0.274 |
| Ca | 127 | 187 | 117 | 101 |
| Mg | 38 | 59 | 17 | 33 |
| Cu | 0.01 | 0.05 | 0.01 | 0.02 |
| Cd | 0.003 | 0.001 | 0.001 | 0.001 |
| Ni | 0.007 | 0.05 | 0.019 | 0.002 |
| Pb | 0.012 | 0.017 | 0.002 | 0.005 |
| Mo | 0.05 | 0.05 | 0.05 | 0.05 |
| As | 0.01 | 0.01 | 0.016 | 0.01 |
| Cr | 0.014 | 0.006 | 0.002 | 0.007 |
| Fe | 1.71 | 5.26 | 1.18 | 1.04 |
Annual average composition of the incoming raw wastewater and the AD effluent from the centrifuges, as well as the discharge threshold defined by legislation for the North Budapest WWTP_ COD: Chemical Oxygen Demand, TSS: total suspended solids, TNK: total Kjeldahl nitrogen, TP: total phosphorus_ The legal threshold on the total nitrogen content (35 mg L-1) also includes the ammonium nitrogen concentration (*)_ All concentrations are in mg L-1_
| pH | COD | Filtered COD | TSS | N(NH3- NH4) | NO2- | NO3- | TNK | PO4-P | TP | |
|---|---|---|---|---|---|---|---|---|---|---|
| Incoming raw wastewater | ||||||||||
| mean | 7.7 | 575.8 | - | 313.7 | 55.3 | 0.49 | 1.5 | 71.4 | 15 | 10.4 |
| error (±2SD) | 0.55 | 427.9 | - | 301.4 | 30.6 | 1 | 3.4 | 33.5 | 11.4 | 7.8 |
| AD effluent | ||||||||||
| mean | 8.1 | 7572.9 | 675.3 | 7842.4 | 1376.1 | - | - | 1688.9 | 53.2 | 263.5 |
| error (±2SD) | 0.3 | 7801.1 | 347 | 8568.9 | 415.3 | - | - | 521.2 | 48.4 | 241.3 |
| Legal thresholds | ||||||||||
| 6.5-9.0 | 125 | 35 | 10 | 35* | 5 | |||||
Volume of the AD effluent in 2017 (first 11 months) processed by different techniques at the North Budapest WWTP_
| Thickening table (m3) | Centrifuge (m3) | Press (m3) | Belt press (m3) | Total (m3) | |
|---|---|---|---|---|---|
| Monthly average volume (m3) | 19 886.61 | 25 965.42 | 3 029.19 | 8 032.57 | 52 381.40 |
| error (±2SD) | ±6795.47 | ±9019.76 | ±1665.19 | ±11984.39 | ±9290.88 |
| Annual total volume (m3) | 218 752.73 | 285 619.61 | 33 321.04 | 32 130.29 | 576 195.38 |
Heavy metal content analysis from two different batches of the harvested microalgae biomass, and food contact material limit_ The symbol (*) shows the concentration value is close to the limit and the symbol (**) means the value exceeds the limit_
| As μg kg-1 | Cd μg kg-1 | Co μg kg-1 | Cr μg kg-1 | Cu mg kg-1 | Mo μg kg-1 | |
|---|---|---|---|---|---|---|
| Batch 2 | 2674* | 52.1 | 567 | 4833 | 84.6** | 650* |
| Batch 3 | 1848 | 80.8 | 631 | 6072 | 38.5* | 1195** |
| Limit | 5000 | 500 | - | 50000 | 50 | 1000 |
| Ni μg kg-1 | Pb μg kg-1 | Zn mg kg-1 | F mg kg-1 | Se mg kg-1 | Hg mg kg-1 | |
| Batch 2 | 24986* | 2638 | 145* | 56.04* | 1.53** | 1.02** |
| Batch 3 | 2166 | 4306 | 255** | 184.4** | 1.02** | 1.02** |
| Limit | 25000 | 50000 | 150 | 100 | 0.75 | 0.5 |
Different input sources used to feed the anaerobic digesters at North Budapest WWTP (2016)_
| Type | Dry matter [tonnes/a] | Organic matter w/w% |
|---|---|---|
| Concentrated sludge from on-site | 17900 | 73 |
| Slaughterhouse waste | 2300 | 83 |
| Dewatered sludge from other WWTPs | 1000 | 69 |
| External liquid waste | 360 | 75 |
Chemical analysis of the unknown precipitation, data in mg kg-1_ TC: total carbon, TN: total nitrogen, TP: total phosphorus, TS: total sulfur_
| Precipitation | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Na | B | Mn | TC | Zn | Ca | Cu | TN | TP | Mo | Hg |
| 1100 | 825 | 649 | 194800 | 142 | 208000 | 60.5 | 27550 | 103877 | 22.5 | 0.5 |
| Se | TS | K | Pb | Fe | Mg | As | Co | Ni | Cd | |
| 9.02 | 3880 | 0.36 | 4.6 | 6.06 | 4830 | 1 | 0.54 | 0.79 | 0.2 |
Settling time of the AD effluent used for growing microalgae at the case study location of the North Budapest WWTP_
| Month of refilling | Settling time (day) | Recovered clean AD effluent (m3) |
|---|---|---|
| April | 34 | 3 |
| May | 23 | 8 |
| June | 27 | 5 |
| August | 13 | 7 |
Mass balance table_ The results are calculated from the added AD effluent composition, current nutrient concentrations and in form of microalgae biomass (both harvested and remaining in the pond) as remaining biomass composition_
| Input in AD effluent | Current nutrient concentrations | In form of microalgae | Loss | |
|---|---|---|---|---|
| Nitrogen | 100% | 41% | 4% | 55% |
| Phosphorus | 100% | 22% | 40% | 38% |