Irrigation with dam recharge and reclaimed water from urban wastewater treatment plant
4 June, 2050
Waste water source
The water originates from the urban wastewater treatment plant of Hisarya, which started operation in 2011. The plant can process up to 1,500 kg/day as BOD5, a total nitrogen load of 275 kg/day and a total phosphorus load 45 kg/day.
‘Irrigation systems’ EAD (Maritsa Branch) owns and manages many facilities for irrigation purposes on the territory of the municipality of Hisarya. Several irrigation channels pass through the municipality: the main one starts from the “Blue River” reservoir and goes to the East and West. The most important is the Lesichovo – Pyasatsnik channel.
The distribution system with gravitational flow delivers water for irrigation of permanent crops, maize and vegetables (tomato, watermelon, etc.).
Waste water treatment description
Nutrient removal : The wastewater treatment plant uses three sequencing batch reactors, three aeration basins (SBR) with aerobic stabilization of sludge, a dewatering machine (centrifuge) and conditioning with lime. They all work together to biologically clean the water. The sewage sludge is composted with wood chips and straw in the same plant.
Pesticide removal : none
Disinfection : see nutrient removal
Suspended solids removal : none
The wastewater treatment plant of Hisarya can handle a daily load of 10,000 to 25,000 person equivalents (p.e.) which correlates to 7,250 m³. The maximum inflow is 453 m3/h in dry weather, in wet weather the flow reaches 1,080 m³/h. The annual discharged quantity of water represents a volume of 1,400,000 m³. The reclaimed water is discharged into the reservoir of the “Blue river” dam, after which it is used for irrigation purposes. The reservoir is also used to breed fish (carp, silver carp…).
Extent of the agricultural beneficiaries
As an example, Vila Hisar irrigates 12.6 ha of vineyards through channels, while Argil Ltd. irrigates 100 ha of vineyards.
The expansion, reconstruction and modernization of the wastewater treatment plant of Hisarya as well as construction of a sewerage network needed 9.5 million euro. According to the owners website, the cost of urban wastewater treatment is 0.255 €/m³, while the industrial waste water with “level of contamination 1” is treated at a cost of 0.30 €/m³, “level of contamination 2” – 0.438 €/m³ and “level of contamination 3” – 0.575 €/m³.
Type of agreement
|The ‘Irrigation systems’ EAD (Maritsa branch) supplies and sells water for irrigation, industry and fish ponds. End-users pay an irrigation cost. The Minister of Agriculture and Food determines the cost for the next irrigational season issuing an order with the approved price for the service, this is done on a yearly basis. The price for the first watering is 3.58 euro/ha (VAT excl.), while for additional water quantities the price is 0.056 euro/m3. The irrigation association uses a private pumping station to transfer water quantities between users.
Mihaylova D, Prokopov Ts, Mihalkov N. 2014. Hydrobiological Investigation of the Activated Sludge from Sequencing Batch Reactors of WWTP – Hisarya, Ecologica Balcanica, 5: 41-47, https://www.researchgate.net/publication/299600792
Analysis of the results coming from WWTP-Hisaryas operation shows that it is designed and built future proof. The modern wastewater treatment plant has all the qualities to work reliably for many years. The massive presence of positive bioindicators and the rare presence or absence of undesirable bioindicators indicates that the aeration basins works well and microorganisms are able to purify the water to a sufficient degree.