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Mikroplastika je vrsta plastičnih odpadkov, ki je v zadnjih letih deležna vse večje pozornosti. Mikroplastika pride v okolje iz različnih virov. Pomembnem vir so očiščene odpadne vode, ki prihajajo iz komunalnih čistilnih naprav. Alternativa konvencionalnim komunalnim čistilnim napravam so lahko rastlinske čistilne naprave. Rastlinske čistilne naprave izkoriščajo zmožnosti rastlin, prsti in mikrobne združbe za čiščenje odpadne vode. Zaradi velikega števila mikroplastike v komunalnih odpadnih vodah se pojavlja vprašanje o možnih vplivih na učinkovitost procesov v rastlinski čistilni napravi. Problematika vpliva mikroplastike na delovanje in na učinkovitost rastlinskih čistilnih napravah je še premalo raziskana in ne povsem razumljena. Vplive mikroplastike smo raziskovali v laboratorijski rastlinski čistilni napravi s podpovršinskim horizontalnim tokom. Opazovali smo vtočne in iztočne parametre amonijevega, nitritnega in nitratnega dušika, kemijske potrebe po kisiku, biokemijske potrebe po kisiku, celotnega organskega ogljika, ortofosfata, klorida, ter pH pred in po začetku dodajanja mikroplastike. Dodajali smo dva tipa mikroplastike, ki jih pogosto najdemo v odpadnih voda – polietilenske mikrokroglice iz kozmetike in poliakrilonitrilna sintetična vlakna. Spremljali smo tudi učinkovitost zadrževanja mikroplastike. Rezultati so pokazali, da rastlinska čistilna naprava dobro obratuje in učinkovito odstranjuje ogljikove, dušikove in fosforjeve spojine. Po dodatku mikroplastike ni prišlo do sprememb pri odstranjevanju ogljikovih spojin, opazili smo pa večje spremembe pri odstranjevanju nitritnega dušika in odstranjevanju ortofosfata. Laboratorijska rastlinska čistilna naprava je učinkovito zadržala skoraj celotni delež dodane mikroplastike. Večina mikroplastike je bila nakopičena v začetnem delu sedimenta čistilne naprave. Microplastics are a type of plastic waste that has received increasing attention in recent years. Microplastics enter the environment from various sources. An important source is the treated wastewater that comes from municipal wastewater treatment plants. Constructed wetlands can be considered as an alternative to conventional municipal treatment plants. Constructed wetlands utilize the properties of plants, soil, and microbial communities to treat wastewater. Due to the large number of microplastics in municipal wastewater, the question arises about the possible effects on the efficiency of the wastewater treatment processes. The influence of microplastics on the operation and efficiency of constructed wetlands has not been sufficiently researched and is not yet fully understood. The effects of microplastics on efficiency were investigated in a laboratory constructed wetland with a subsurface horizontal flow. We determined ammonium, nitrite and nitrate nitrogen, chemical oxygen demand, biochemical oxygen demand, total organic carbon, orthophosphate, chloride and pH before and after the microplastics addition. We added two types of microplastics that are often found in wastewater – polyethylene microbeads from cosmetics and polyacrylonitrile synthetic fibers. We also monitored the efficiency of microplastic retention. The results showed that the constructed wetland operates well and effectively removes carbon, nitrogen and phosphorus compounds. After the addition of microplastics, there were no changes in the removal of carbon compounds, but we observed greater changes in the removal of nitrite nitrogen and the removal of orthophosphate. The laboratory constructed wetland effectively retained almost all of the added microplastics. Most of the microplastics accumulated in the initial part of the sediment of the constructed wetland. |
