Digested Piggery Wastewater Research Articles

Nanoscale Zero‐Valent Iron for Sulfide Removal from Digested Piggery Wastewater

The removal of dissolved sulfides in water and wastewater by nanoscale zero‐valent iron (nZVI) was examined in the study. Both laboratory batch studies and a pilot test in a 50,000‐pig farm were conducted. Laboratory studies indicated that the sulfide removal with nZVI was a function of pH where an increase in pH decreased removal rates. The pH effect on the sulfide removal with nZVI is attributed to the formation of FeS through the precipitation of Fe(II) and sulfide. The saturated adsorption capacities determined by the Langmuir model were 821.2, 486.3, and 359.7 mg/g at pH values 4, 7, and 12, respectively, for nZVI, largely higher than conventional adsorbents such as activated carbon and impregnated activated carbon. The surface characterization of sulfide‐laden nZVI using XPS and TGA indicated the formation of iron sulfide, disulfide, and polysulfide that may account for the high adsorption capacity of nZVI towards sulfide. The pilot study showed the effectiveness of nZVI for sulfide removal; however, the adsorption capacity is almost 50 times less than that determined in the laboratory studies during the testing period of 30 d. The complexity of digested wastewater constituents may limit the effectiveness of nZVI. Microbial analysis suggested that the impact of nZVI on the change of microbial species distribution was relatively noticeable after the addition of nZVI.

Ammonium nitrogen removal in batch cultures treating digested piggery wastewater with microalgae Oedogonium sp.

Due to the nutrient characteristics of the high concentration of available ammonium in digested piggery wastewater (DPW), microalgae can be used to treat DPW before its final discharge. Four green microalgae (Hydrodictyaceae reticulatum Lag, Scenedesmus obliquus, Oedogonium sp. and Chlorella pyrenoidosa) and three blue-green algae (Anabaena flos-aquae, Oscillatoria amoena Gom and Spirulina platensis) were used to remove the nutrients (N, P, C), especially ammonium nitrogen (NH4(+)-N), from diluted DPW with 300 mg/L algae density in batch tests. The microalgae with the best NH4(+)-N nutrient removal was then selected for further optimization of the variables to improve NH4(+)-N removal efficiency using a central composite design (CCD) experiment. Taking into account the nutrient removal efficiency, Oedogonium sp. showed the best performance (reduction of 95.9% NH4(+)-N, 92.9% total phosphorus (TP) and 62.5% chemical oxygen demand (COD)) based on the results of the batch tests. The CCD results suggested that the optimal values of variables were initial Oedogonium sp. density of 399.2 mg/L and DPW diluted by 16.3, while the predicted value of NH4(+)-N removal efficiency obtained was 97.0%.

Aerobic Granulation in a Sequencing Batch Reactor for the Treatment of Piggery Wastewater

This study investigated the formation of aerobic granules fed with digested piggery wastewater. After 42 days of cultivation, small yellow granules with mean diameter of 0.4 mm were first observed in the reactor. Scanning electron microscope pictures showed the granules were compact, round structures with clear outer shapes and mainly composed of filamentous bacteria. Maximum chemical oxygen demand and ammonia removal ratios were 90.1 and 91.7%, respectively. The Monod equation, which was used to describe ammonium utilization, yielded a maximum rate of 6.25 mg (g volatile suspended solids)(-1) h(-1). The measurement of extracellular polymeric substances (EPS) content and three-dimensional excitation and emission matrix results showed that the EPS concentration increased during the granulation process. Fluorescence in situ hybridization analysis showed significant amounts of nitrifying bacteria in the aerobic granules. Results in this study provide insights to the treatment of piggery wastewater using aerobic granular sludge.

Dissolved organic matter in digested piggery wastewater from combined treatment process

ABSTRACT The temporal and spatial variation of dissolved organic matter in the processes of hydrolytic acidification and biological contact oxidation during post-treatment of digested piggery wastewater were characterized systematically by means of ion chromatography, fluorescence spectra, and ultraviolet spectra in this study. The highest removal efficiencies of chemical oxygen demand and nitrogen have been achieved when the 1/3 effluent of biological contact oxidation reactor was backflow into the reactor of hydrolytic acidification. It was found that the concentrations of total organic acids were 283.6 mg/L at the first 2 h of hydrolytic reaction and 305.5 mg/L at the beginning of recirculation between the two reactors and then decreased to around 200 mg/L and keep stable. The results of synchronous and three-dimensional excitation–emission matrix fluorescence spectroscopy revealed that the protein-like fluorescence peaks were identified in the hydrolytic acidification reactor and their intensities increased gradually along with hydrolytic time increasing. Moreover, the fulvic acid-like fluorescence peaks in biological contact oxidation reactor were observed, and the intensity increased gradually. The synchronous intensity of 277 nm wavelength was significantly correlated with the total organic acids concentration. Variation of SUVA254 and E 253/E 203 during the hydrolytic acidification process indicated that concentrations of aromatic and unsaturated compounds slightly increase and those aromatic compounds are not stable. However, SUVA254 and E 253/E 203 decreased rapidly in the biological contact oxidation reactor, which suggested that easily degradable organic matters had been consumed rapidly.

Mitigating ammonia inhibition of thermophilic anaerobic treatment of digested piggery wastewater: Use of pH reduction, zeolite, biomass and humic acid

High free ammonia released during anaerobic digestion of livestock wastes is widely known to inhibit methanogenic microorganisms and result in low methane production. This was encountered during our earlier thermophilic semi-continuously fed continuously-stirred tank reactor (CSTR) treatment of piggery wastewater. This study explored chemical and biological means to mitigate ammonia inhibition on thermophilic anaerobic treatment of piggery wastewater with the aim to increase organic volatile carbon reduction and methane production. A series of thermophilic anaerobic batch experiments were conducted on the digested piggery effluent to investigate the effects of pH reduction (pH 8.3 to 7.5, 7.0 and 6.5) and additions of biomass (10% v/v and 19% v/v anaerobic digested piggery biomass and aerobic-anaerobic digested municipal biomass), natural zeolite (10, 15 and 20 g/L) and humic acid (1, 5 and 10 g/L) on methane production at 55 °C for 9–11 days. Reduction of the wastewater pH from its initial pH of 8.3 to 6.5 produced the greatest stimulation of methane production (3.4 fold) coupled with reductions in free ammonia (38 fold) and total volatile fatty acids (58% TVFA), particularly acetate and propionate. Addition of 10–20 g/L zeolite to piggery wastewater with and without pH reduction to 6.5 further enhanced total VFA reduction and methane production over their respective controls, with 20 g/L zeolite producing the highest enhancement effect despite the ammonia-nitrogen concentrations of the treated wastewaters remaining high. Without pH reduction, zeolite concentration up to 20 g/L was required to achieve comparable methane enhancement as the pH-reduced wastewater at pH 6.5. Although biomass (10% v/v piggery and municipal wastes) and low humic acid (1 and 5 g/L) additions enhanced total VFA reduction and methane production, they elevated the residual effluent total COD concentrations over the control wastewaters (pH-unadjusted and pH-reduced) unlike zeolite treatment. The outcomes from these batch experiments support the use of pH reduction to 6.5 and zeolite treatment (10–20 g/L) as effective strategies to mitigate ammonia inhibition of the thermophilic anaerobic treatment of piggery wastewater.

Utilising bacterial communities associated with digested piggery effluent as a primary food source for the batch culture of Moina australiensis

In this study, a cladoceran planktonic invertebrate, Moina australiensis was uniquely cultured in two stage digested piggery wastewater and fed associated piggery wastewater bacteria. The viability of M. australiensis cultured in digested piggery wastewater under closed dark conditions to limit phytoplankton activity was tested by determining suitable effluent total ammonia nitrogen (TAN) concentrations. The highest total M. australiensis biomass production 0.94 ± 0.47 g and the rate of population increase ( r) 0.15 ± 0.08 was recorded in the 30 mg l −1 TAN concentration treatment. The lowest ‘ r’ values and decreased biomass production was observed with increasing TAN concentration levels. This study, also focused on profiling and quantification of the associated bacterial populations in the wastewater culture media and within the digestive tract of M. australiensis by denaturing gradient gel electrophoresis (DGGE) and real-time polymerase chain reaction (RT-PCR) which revealed the feeding specificity of M. australiensis towards “γ- Proteobacteria.”

Biological nutrient removal by a sequencing batch reactor (SBR) using an internal organic carbon source in digested piggery wastewater

Experiments in a lab-scale SBR were conducted to demonstrate the feasibility of using an internal carbon source (non-digested pig manure) for biological nitrogen and phosphorus removal in digested piggery wastewater. The internal C-source used for denitrification had similar effects to acetate. 99.8% of nitrogen and 97.8% of phosphate were removed in the SBR, from an initial content in the feed of 900 mg/l ammonia and 90 mg/l phosphate.