Stabilization and solidification process of hazardous sludge generated during wastewater treatment process

Proces stabilizacije/solidifikacije (S/S) se smatra najboljom dostupnom tehnikom za tretman industrijskog muljevitog i čvrstog otpada. U okviru disertacije ispitivan je razvoj i optimizacija S/S procesa otpadnog mulja koji nastaje tretmanom otpadne vode iz primarne topionice bakra, kao i stabilizacija klinkera tokom tretmana otpadnih muljeva iz hidrometaluškog procesa dobijanja cinka koji se odlikuju visokim sadržajem osnovnih i toksičnih metala (Cu, Zn, Pb, Ni i As). Optimizacija S/S procesa otpadnog mulja iz primarne topionice bakra je vršena variranjem odnosa mulj/agens za stabilizaciju i sastava agensa. Kao agens za stabilizaciju ispitivan je leteći pepeo u smešama sa kalcijum(II)-hidroksidom i kompozitnim portland cementom. Efikasnost S/S procesa je određena merenjem pritisne čvrstoće i stabilnosti solidifikata na luženje kontaminenata upotrebom dva standardna testa: TCLP i EN 12457-4. Kako su primenjeni standardni testovi dali različitu klasifikaciju pojedinih solidifikata kao opasnog ili neopasnog otpada, u disertaciji je predložena i primenjena postavka dugoročnog testa luženja pod realnim uslovima sredine koji se sastoji u izlaganju solidifikata uticaju atmosferalija tokom godinu dana i skupljanju drenažne vode tokom zimskog i letnjeg perioda, a u cilju određivanja realnije ocene stabilnosti tretiranog otpada. Utvrđeno je da nivo izluženja kontaminenata zavisi od puferskog kapaciteta solidifikata, određenog primenom ANC testa. Faze u strukturi solidifikata koje su uzrokovale razlike u pritisnoj čvrstoći i stabilnosti na luženje između dobijenih solidifikata nisu otkrivene tokom mineraloške analize primenom XRD metode usled generalno amorfne strukture solidifikovane matrice. Diferencijalna ANC analiza (d-ANC) predstavlja efikasnu alternativu u ispitivanju strukture solidifikata, a u disertaciji su njeni rezultati upareni sa Eh-pH dijagramima što predstavlja novitet u primeni ove analize. Primena modifikovane d-ANC analize je determinisala prisustvo neizreagovanog kalcijum(II)-hidroksida, dodatog u višku, koji uzrokuje povećanje puferskog kapaciteta i stabilnost na luženje solidifikata, ali i pad pritisne čvrstoće. Prisustvo ove faze je potvrđeno SEM analizom uzoraka solidifikata...Stabilization and solidification process is considered to be the best available technique for the treatment of industrial waste sludge and solid waste. This PhD thesis presents investigations of development and optimization of the S/S process of waste sludge generated during the wastewater treatment in primary copper smelter, as well as the stabilization process of clinker formed during the treatment of waste sludges with copper content from hydrometallurgical zinc processing which are characterized by a high content of base and toxic metals (Cu, Zn, Pb, Ni i As). The optimization of the S/S process of wastewater treatment sludge from primary copper smelter is done by varying the ratio sludge/binder and the composition of the binder (the agent for stabilization). Fly ash (FA), individually or in mixtures with hydrated lime (HL) and composite Portland cement (PC), was investigated as the stabilization agent. The efficiency of the S/S process is determined by measuring the unconfined compressive strength (UCS) and leaching stability of solidificates by using two standard leaching tests: TCLP and EN 12457-4. The two leaching tests gave different classification of the same treated waste as hazardous or non-hazardous. For that reason the setting of a long-term leaching test under the real environmental conditions is proposed and applied within the PhD thesis. The test includes exposure of solidificates to the effect of atmospheric water during one year and collection of drainage water during the summer and winter season in order to determine a more realistic assessment of the stability of the treated waste. It is determined that the leaching level of contaminants depends on the buffer capacity of the solidificates and it was analyzed by using the ANC test. Phases in the solidified structure that caused the differences in the UCS and leaching stability between the obtained solidificates were not detected in the mineralogical analysis done by the XRD method due to the generally amorphous structure of the solidified matrix. Differential ANC analysis (d-ANC) is an effective alternative in examining the solidified structure, and its results are paired with Eh-pH diagrams, which is a novelty in the application of this analysis presented in the PhD thesis. The application of the modified d-ANC analysis determined the presence of unreacted calcium(II)-hydroxide added in excess, which caused an increase of the buffer capacity and leaching stability of solidificates, but also a decrease of the UCS..