[1. Rulkens, W.H., Klapwijk, A., & Willersb, H.C. (1998). Recovery of valuable nitrogen compounds from agricultural liquid wastes: potential possibilities, bottlenecks and future technological challenges. Environ. Pollut. 102 (S1), 727-735. DOI: 10.1016/S0269-7491(98)80105-X.10.1016/S0269-7491(98)80105-X]Search in Google Scholar
[2. Pawełczyk, A. & Muraviev, D. (2003). The integrated treatment for purification of liquid pig wastes. Przem. Chem. 82 (8-9), 861-863, (in Polish).]Search in Google Scholar
[3. Kowalski, Z., Makara, A., Hoffmann, J. & Hoffmann, K. (2012). Research report from realization of grant No 14-0003-10/2010. Obtaining of NPK type fertilizers from the pig manure using cleaner production methods. Cracow University of Technology, Cracow, (not published), (in Polish).]Search in Google Scholar
[4. Hjorth, M., Christensen, K.V., Christensen, M.L. & Sommer, S.G. (2010). Solid-liquid separation of animal slurry in theory and practice. A review. Agron. Sustain. Dev. 30 (1), 153-180. DOI: 10.1051/agro/2009010.10.1051/agro/2009010]Search in Google Scholar
[5. González-Fernández, C., Nieto-Diez, P.P., León- -Cofreces, C. & García-Encina, P.A. (2008). Solids and nutrients removals from the liquid fraction of swine slurry through screening and fl occulation treatment and infl uence of these processes on anaerobic biodegradability. Bioresour. Technol. 99, 6233-6239. DOI: 10.1016/j. biortech.2007.12.022.]Search in Google Scholar
[6. Kowalski, Z., Makara, A., Hoffmann, J. & Hoffmann, K. (2012). Polish patent application P. 400044, (in Polish).]Search in Google Scholar
[7. Polish standard PN-ISO 6060:2006. Water quality - Determination of the chemical oxygen demand, (in Polish).]Search in Google Scholar
[8. Polish standard PN-EN 25663. Water quality - Determination of Kjeldahl nitrogen - Method after mineralization with selenium, (in Polish).]Search in Google Scholar