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Jolanta Bohdziewicz, Mariusz Kuglarz and Klaudiusz Grűbel

Abstract

The article presents the results of determining the most appropriate conditions of microwave sludge pre-treatment (500-1200 W), prior to its anaerobic digestion in a continuous mode. The assessment of the pre-treatment conditions (microwave power, sludge temperature after pre-treatment) was based on: the release of organic (COD, protein) and inorganic (NH4 +, PO4 3-) substances into liquid, the quantity of methane produced, sludge higienisation and the susceptibility of the pre-treated sludge to dewatering. The power of the microwaves applied did not play significant role on the pre-treatment effectiveness. Taking into account the fact that sludge pre-treatment by microwave irradiation requires the delivery of energy, the pre-treatment by microwaves of higher power (1200 W) and resulting in sludge temperature of 70°C was recommended for further experiments. Sludge pre-treatment by means of microwave irradiation as a pre-treatment step influenced the effectiveness of the subsequent anaerobic digestion, conducted in continuous conditions, in a positive way. The largest amount of biogas was obtained for HRT in the range of 15-20 days. As compared to the sludge which did not undergo pre-treatment, daily biogas production and biogas yield increased by 18-41% and 13-35% respectively. The combination of microwave pre-treatment and mesophilic anaerobic digestion ensured the elimination of pathogens (Salmonella spp., Escherichia coli).

Open access

Mariusz Kuglarz, Klaudiusz Grübel and Jolanta Bohdziewicz

Abstract

The aim of the study was to develop an effective treatment of post-digestion liquors highly-loaded with biogenic and organic substances. The scope of the research project encompassed: mesophilic anaerobic digestion of waste activated sludge (WAS) as well as the treatment of post-digestion liquors, coming from the most appropriate HRT value of 25 days, in the process of ammonium magnesium phosphate (struvite) precipitation targeted at ammonia nitrogen binding and a subsequent reverse osmosis (RO) process. It was established that the method combining chemical precipitation and high-pressure filtration ensures a high degree of contaminants removal allowing for a direct release of treated liquors into the natural reservoir. However, in order to decrease the residual NH4 + concentration (6.1 mg NH4 +/dm3) in the purified post-digestion liquors below the level allowing for a direct release to the natural reservoir, it turned out to be necessary to apply increased molar ratio of magnesium and phosphates (Mg:NH4 +: PO4 3-= 1.5:1:1.5).

Open access

Anna Świerczyńska, Jolanta Bohdziewicz and Ewa Puszczało

Abstract

The aim of presented study which was associated with modification of the various work cycle phases duration in the membrane bioreactor, was to reduce the concentration of phosphate phosphorus during the leachate co-treatment with dairy wastewater. The experimental set-up was comprised of the membrane bioreactor equipped with the immersed membrane module installed inside the reactor chamber, and the equalization tank. During the co-treatment experiment performance the excessive activated sludge was constantly removed from the membrane bioreactor in order to keep its concentration at 3.5 g/dm3. The load of the sludge with the contaminants was equal to 0.06 g COD/g d.m. d. The concentration of oxygen was equal to 3 mg/dm3. The share of the leachates in the co-treated mixture was equal to 10% vol. The membrane bioreactor worked as the sequential biological reactor, in two cycles per day. Duration of each phase was equal as follows: filling - 10 min - with concurrent mixing phase lasting for 4 h, aeration phase - 1 h, sedimentation - 30 min and removal from purified wastewater - 30 min. After 4 weeks under these conditions, the modification of the sequential membrane bioreactor’s work cycle was made. The duration of particular phases was shortened and two phases of denitrification and nitrification were introduced. Work cycle phases were modified as follows: filling - 10 min - with concurrent mixing phase lasting for 3 h, aeration phase - 4 h, mixing phase - 1 h, aeration phase - 3 h, sedimentation - 30 min and removal from purified wastewater - 30 min. Based on research, it was found that the change in membrane bioreactors’ work cycle affects the effectiveness of treated mixture. It was found that the applied modification of phases of the cycle of the MSBR did not affect the concentration of organic compounds and the no significant changes in the concentration of ammonium and nitrate nitrogen in the effluent from the bioreactor were observed, however, the total nitrogen removal efficiency increased by 50%. Alteration of MSBR reactor particular phases duration caused reduction of concentration of P-PO4 3 from 4.7 to 2.9 mg/dm3.

Open access

Jolanta Bohdziewicz and Gabriela Liszczyk

Abstract

Wide use of bisphenol A (BPA) in production of polycarbonates and plastic food packaging cause increase of concentration of BPA in the environment. Both in surface water, underground water and seawater BPA was frequently detected in different concentrations. Emerging problem is adsorption of BPA on sewage, because it could be considered as an additional source of pollution, if it is used as a fertilizer in agricultural sectors. Absorbed BPA on sewage sludge stays persistent in the environment and generates adverse biological effects in endocrine system. Because of ecological safety, exploration of potential techniques to remove BPA to the level, which does not give adverse effect on natural environment is necessary. In this study the adsorption of BPA from simulated water onto commercial activated carbons was investigated. On the basis of experimental data the kinetics and type of sorption were determined.