**2.2 Physical and chemical methods**

The following changes in physical and chemical properties of the solid and liquid wastes were monitored: pH, dry mater (DM), inorganic (IM) and organic (OM) matter, ammonium ions (NH4 +), total nitrogen (Nt), chemical oxygen demand (COD), soluble and insoluble substances and C:N ratio.

The Sanitation of Animal Waste Using Anaerobic Stabilization 53

absorption of insoluble substances on a filter, drying the evaporation residue at 105°C and determining its weight. COD was determined on the basis of organic substances oxidation in sample by potassium dichromate in sulfuric acid medium during 2-hour boiling in a COD reactor (HACH Company, Loveland, Colorado, USA). Portion of samples for Nt determinations were digested using a HACH-Digesdahl apparatus (HACH Company, Loveland, Colorado, USA). Nt was distilled with NaOH (40 %) (Bremner, 1996). The C content was calculated according to the content of OM by the method of Navarro et al.

The physical and chemical properties (pH, DM, IM, OM, NH4+, Nt,) of solid animal wastes, as well as the number of demaged eggs were expressed as mean values ± standard deviation

Significance of differences between experimental and control groups of parasites were determined using Student t-test, ANOVA and Dunnet Multiple Comparison test at the

Investigations were carried out under operating conditions of the large-capacity pig farm in Slovak Republic (Picture 3). Technological equipment for anaerobic treatment of pig slurry on the principle of methanogenesis with the production of biogas was built up on the farm (Picture 4). Pig slurry was treated in the bioreactor (2 500 m3) manufactured by Mostáreň Brezno under the agreement with the firm BAUER Voitsberg. The stirring of the substrate in this reactor was done at the expense of energy of the generated biogas. Mean daily input of raw pig slurry in bioreactor of biogas plant varied between 78 and 144 m3. The volume of digested slurry after methanogenesis was equal to that of the input. Two lagoons were the part of the biogas plant. The volume of larger lagoon is 20 000 m3 (Picture 5) and that of smaller lagoon is 5 000 m3. Both lagoons serve as reservoirs of digested slurry. Liquid fraction from the smaller lagoon was carried away and spread on fields. The presence and survival of parasite eggs were studied in the larger lagoon. Samples were taken from raw slurry collecting basin before the inlet in to bioreactor (input samples), from outlet of digested slurry after methanogenesis in bioreactor (output samples), from supernatant (liquid fraction) and from lagoon sludge (solid fraction - sediment). The slurry samples for parasitological and physical and chemical examination were collected monthly during 29

Slurry from the pig farm stored in the collecting basin showed a considerable variability during the period of study (Table 1). Compared with mean pH value of 7.12 ± 0.26, pH raw slurry in the month 11, 17 and 21 was lower, ranging between 6.61 and 6.95. The most conspicuous differences were recorded in DM content, which is most likely associated with the amount of process water use. The DM content in raw slurry determined during the period studied ranged from 0.81 % to 5.30 %. The amount of NH4+ in raw slurry was between 821 mg.l-1 and 1 774 mg.l-1. Chemical oxygen demand (COD) for that period varied from 2 000 mg.l-1 to 22 530 mg.l-1. The mean contents of Nt, in slurry was 1 445 ± 420 mg.l-1.

(1993) to obtain the C:N ratio.

levels of significance 0.05; 0.01 and 0.001 (Statistica 6.0).

**a) Anaerobic stabilisation of liquid animal wastes** 

**2.3 Statistical analysis** 

( x ±SD).

**Results** 

month.

Picture 1. Polyurethane carrier with adhered *A. suum* eggs

Picture 2. Perforated plastic nets with the carriers

The samples were examined for the pH (1:10 water extract) using a pH electrode (HACH Company, Loveland, Colorado, USA). Dry matter (drying at 105°C to a constant weight), residum-on-ignition (550°C for 4 h), and water soluble ammonium nitrogen (NH4 +) by titration (Mulvaney, 1996). Soluble and insoluble substances were determined by evaporation of the known amount of homogeneous sample filtrate on a water bath after absorption of insoluble substances on a filter, drying the evaporation residue at 105°C and determining its weight. COD was determined on the basis of organic substances oxidation in sample by potassium dichromate in sulfuric acid medium during 2-hour boiling in a COD reactor (HACH Company, Loveland, Colorado, USA). Portion of samples for Nt determinations were digested using a HACH-Digesdahl apparatus (HACH Company, Loveland, Colorado, USA). Nt was distilled with NaOH (40 %) (Bremner, 1996). The C content was calculated according to the content of OM by the method of Navarro et al. (1993) to obtain the C:N ratio.
