Rastlinska čistilna naprava kot vir vode in rastlinskih hranil v kmetijstvu

Volk, Anja (author), Žgajnar Gotvajn, Andreja (mentor), Istenič, Darja (comentor)

Dandanes želimo v skladu z načeli krožnega gospodarstva in ponovne rabe virov očiščeno komunalno odpadno vodo iz čistilnih naprav ponovno uporabiti. Eden od obetavnih načinov uporabe očiščene komunalne odpadne vode je gnojenje in namakanje v kmetijstvu. Za čiščenje komunalne odpadne vode iz manjših naselij se pogosto uporabljajo rastlinske čistilne naprave (RČN). RČN navadno obratujejo glede na prepisane parametre za izpust v okolje in omogočajo tudi odstranjevanje hranil. V primeru ponovne uporabe očiščene vode v kmetijstvu je odstranjevanje hranil nezaželeno, saj s tem lahko nadomestimo del mineralnih gnojil. Delovanje RČN je zato potrebno prilagodi tako, da se hranila v času vegetacijske sezone v procesu čiščenja ne odstranijo, medtem ko mora biti odstranjevanje zagotovljeno v zimskem času, ko se voda spušča neposredno v okolje. V tej nalogi smo zato spremljali učinkovitost čiščenja in odstranjevanja hranil iz komunalne odpadne vode v RČN z navpičnim tokom v poletnem in zimskem načinu obratovanja. Pri zimskem načinu obratovanja je bil uveden povratek dela očiščene vode nazaj v anaerobni primarni usedalnik, s čimer smo želeli povečati odstranjevanje celokupnega dušika. V različnih načinih obratovanja RČN smo na dotoku v usedalnik, dotoku na RČN in iztoku spremljali celotni dušik (TN), Kjeldahlov dušik, amonijev dušik, nitritni dušik, nitratni dušik, KPK, BPK5, skupne suspendirane snovi, celotni fosfor, pH, koncentracijo raztopljenega kisika ter električno prevodnost. Rezultati so pokazali, da RČN z navpičnim tokom omogoča učinkovito odstranjevanje organskih snovi in proizvodnjo nitrificiranih iztokov, ki se lahko uporabijo za gnojenje in namakanje v kmetijstvu. Pri zimskem načinu obratovanja z vračanjem dela iztoka nazaj v primarno obdelavo nismo dosegli želene odstranitve TN zaradi aerobnih pogojev v usedalniku. Ugotovili smo, da lahko z RČN za 40 PE (manjše naselje) namakamo 631 m2 njive pšenice, pri čemer bi prihranili 40 % dušičnih in 39 % fosfornih gnojil. Potrebno pa bi bilo dognojevanje.

• Language: Slovenian
• Keywords: denitrifikacija, krožna ekonomija, nitrifikacija, ponovna raba hranil, ponovna uporaba odpadne vode, recikel
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2023
• PID: 20.500.12556/RUL-145706
• COBISS.SI-ID: 153401603
• Publication date in RUL: 10.05.2023

Secondary language

• Language: English
• Title: Treatment wetland as a source of water and nutrients for agriculture

Abstract

Today, in accordance with the principles of the circular economy and the re-use of resources, we want to use treated urban wastewater from treatment wetlands. One promising use of treated urban wastewater is fertilisation and irrigation in agriculture. Treatment wetlands are often used to treat urban wastewater from small settlements. They usually operate according to prescribed parameters for discharge to the environment and also allow removal of nutrients. In the case of re-use of treated water in agriculture, the removal of nutrients is undesirable, as it can replace part of the mineral fertiliser. Therefore, the operation of the treatment wetlands needs to be adjusted so that nutrients are not removed in the treatment process during the growing season, while removal must be ensured in the winter when the water is discharged directly into the environment. In this work, we monitored the efficiency of treatment and removal of nutrients from municipal wastewater in a vertical-flow treatment wetland in summer and winter operating modes. In winter operating mode, a recycle of part of the treated water back to the anaerobic primary settling tank was introduced in order to increase the removal of total nitrogen. During the different operating modes of the vertical-flow treatment wetland, total nitrogen (TN), Kjeldahl nitrogen, ammonium nitrogen, nitrite nitrogen, nitrate nitrogen, COD, BOD5, total suspended solids, total phosphorus, pH, dissolved oxygen and electrical conductivity were monitored at the influent to the settling tank, the influent to the treatment wetland and in the effluent. It was concluded that the treatment wetland with vertical flow allows efficient removal of organic matter and production of nitrified effluents that can be used for fertilisation and irrigation purposes in agriculture. In winter operating mode, by recycling part of the effluent back to primary treatment, the desired TN removal was not achieved due to aerobic conditions in the settling tank. The conclusion is that we can irrigate 631 m2 of wheat field with treatment wetland for 40 PE (smaller settlement), saving 40 % of nitrogen and 39 % of phosphorus fertilizers. However, additional fertilisation would be necessary.

• Keywords: circular economy, denitrification, nitrification, nutrient reuse, recycling, wastewater reuse