Full-scale simultaneous partial nitrification, anammox, and denitrification process for treating swine wastewater.

A full-scale swine-wastewater activated sludge treatment plant that contains naturally enriched anammox biofilms was investigated for 2 years. Red biofilm in this system included Planctomycetes at a maximum of 62.5% of the total bacteria diversity, including Candidatus Jettenia and Candidatus Brocadia. The plant was operated with an influent containing 1,104 ± 513 mg/L biochemical oxygen demand (BOD) and 629 ± 198 mg/L total nitrogen (TN) (BOD/N of 1.78 ± 0.58) at a volumetric BOD loading rate of 0.32 ± 0.12 kg/m3/d. Notwithstanding drastically varying influent concentrations, BOD removal efficiency was stable at 95 ± 4%. However, TN removal fluctuated at 75 ± 14%. Dissolved oxygen (DO) concentrations in the aeration tank were 0.06-2.0 mg/L. DO concentration greatly affected nitrogen removal, e.g. when DO was lower than 0.3 mg/L, total inorganic nitrogen removal was 61 ± 14% (≤20 °C), 78 ± 16% (20-30 °C), and 75 ± 12% (≥30 °C), whereas at higher DO concentrations, removal rates were 47 ± 13%, 55 ± 16%, and 68%, respectively. As BOD concentration in the influent was limited compared to nitrogen concentration, nitrogen was likely removed by simultaneous nitrification, anammox, and denitrification (SNAD) under microaerobic conditions. Maintaining low DO concentrations would therefore be a simple method to improve nitrogen removal during SNAD processes for swine-wastewater treatment with fluctuating influent.

Effects of thiosulfate addition on ammonia and nitrogen removal in biofilters packed with Oyaishi (pumice tuff).

Ammonia removal is achieved partly by absorption and nitrification in biofilters, resulting in the accumulation of nitrogen and the necessity of treating the effluent water. We investigated the effects of thiosulfate addition to a biofilter containing pumice tuff for ammonia and nitrogen removal in a laboratory-scale experiment. The addition of thiosulfate to the circulating water led to a decreased nitrate and nitrite along with an increase of sulfate. The inorganic nitrogen in the circulating water decreased by up to 44% with thiosulfate addition compared to without thiosulfate. Batch experiments revealed that denitrification activity decreased exponentially along with increases in dissolved oxygen; however, approximately 30% of denitrification activity was maintained at dissolved oxygen concentration of 3.3 mg/L. Metabarcoding of 16S rRNA genes indicated that the genus Thiobacillus had a relative abundance of 0.002%-0.016% of total bacteria in the biofilter packing material. The circulating water pH was decreased below 5 with sulfur oxidation, and ammonium was accumulated without pH control resulting in a decrease in the relative abundance of the family Nitrosomonadaceae. Its relative abundance increased with control of pH to near neutral, indicating that ammonia-oxidizing activity could be maintained by adjusting pH. Thiosulfate addition could stimulate nitrogen removal by sulfur-dependent denitrification in biofiltration systems.

Tolerance of anammox reactor packed with zeolite to partial supply of nitrite or ammonium using purified livestock wastewater.

Anammox reaction requires nitrite and ammonium in the ratio of 1.1-1.3. However, controlling a partial nitrification process prior to the anammox process to maintain this ratio in an influent to the anammox reactor is not easy. In this study, the effect of zeolite on anammox reaction was investigated to determine a method of ammonium preservation in case of partial supply of nitrite or ammonium. Up-flow column type anammox reactors, filled with either zeolite or non-woven fabric, were operated in two-week intervals with purified livestock wastewater containing either ammonium or nitrite. The zeolite reactor showed significantly higher nitrogen removal rates than the non-woven fabric reactor for both influents. When the influent contained ammonium, it was adsorbed onto zeolite, while anammox tolerated starvation for two weeks. In a subsequent reaction cycle, when the influent contained nitrite, anammox used the nitrite and the ammonium desorbed from zeolite. The highest nitrogen removal rates were 0.71 and 0.29 gN/L/day, observed in the zeolite reactor, with the ammonium and nitrite influents, respectively. The limiting factor for reactor performance was zeolite saturation level when the influent contained ammonium and anammox reaction rate when the influent contained nitrite. This study demonstrated that zeolite can buffer the unbalance of the nitrite to ammonium ratio in an anammox reaction, and showed the scopes for improvement under each influent.

Treatment of swine wastewater in continuous activated sludge systems under different dissolved oxygen conditions: Reactor operation and evaluation using modelling.

Swine wastewater was treated in two continuously aerated activated sludge (AS) systems at high (AS1: 1.7-2.6 mg/L) and low (AS2: 0.04-0.08 mg/L) dissolved oxygen (DO), and at three temperatures (10, 20, and 30 °C). Biochemical oxygen demand (BOD) removal was >94.8%. Meanwhile, total nitrogen (N) removal was significantly higher in AS2, at 64, 89, and 88%, than in AS1, at 12, 24, and 46%, for 10, 20, and 30 °C, respectively. The experimental data were considered in a simulation study using an AS model for BOD and N removal, which also included nitrite, free ammonia, free nitrous acid, and temperature. Simulations at high-DO showed that ammonium was partly oxidized into nitrate but not removed, whereas at low-DO ammonium was removed mainly through the nitrite shortcut in simultaneous nitrification-denitrification. This study demonstrates that treatment at low-DO is an effective method for removing N, and modelling a helpful tool for its optimization.

Characterization of the denitrifying bacterial community in a full-scale rockwool biofilter for compost waste-gas treatment.

The potential denitrification activity and the composition of the denitrifying bacterial community in a full-scale rockwool biofilter used for treating livestock manure composting emissions were analyzed. Packing material sampled from the rockwool biofilter was anoxically batch-incubated with 15N-labeled nitrate in the presence of different electron donors (compost extract, ammonium, hydrogen sulfide, propionate, and acetate), and responses were compared with those of activated sludge from a livestock wastewater treatment facility. Overnight batch-incubation showed that potential denitrification activity for the rockwool samples was higher with added compost extract than with other potential electron donors. The number of 16S rRNA and nosZ genes in the rockwool samples were in the range of 1.64-3.27 × 109 and 0.28-2.27 × 108 copies/g dry, respectively. Denaturing gradient gel electrophoresis analysis targeting nirK, nirS, and nosZ genes indicated that the distribution of nir genes was spread in a vertical direction and the distribution of nosZ genes was spread horizontally within the biofilter. The corresponding denitrifying enzymes were mainly related to those from Phyllobacteriaceae, Bradyrhizobiaceae, and Alcaligenaceae bacteria and to environmental clones retrieved from agricultural soil, activated sludge, freshwater environments, and guts of earthworms or other invertebrates. A nosZ gene fragment having 99% nucleotide sequence identity with that of Oligotropha carboxidovorans was also detected. Some nirK fragments were related to NirK from micro-aerobic environments. Thus, denitrification in this full-scale rockwool biofilter might be achieved by a consortium of denitrifying bacteria adapted to the intensely aerated ecosystem and utilizing mainly organic matter supplied by the livestock manure composting waste-gas stream.

Anammox biofilm in activated sludge swine wastewater treatment plants.

We investigated anammox with a focus on biofilm in 10 wastewater treatment plants (WWTPs) that use activated sludge treatment of swine wastewater. In three plants, we found red biofilms in aeration tanks or final sedimentation tanks. The biofilm had higher anammox 16S rRNA gene copy numbers (up to 1.35 × 1012 copies/g-VSS) and higher anammox activity (up to 295 µmoL/g-ignition loss/h) than suspended solids in the same tank. Pyrosequencing analysis revealed that Planctomycetes accounted for up to 17.7% of total reads in the biofilm. Most of them were related to Candidatus Brocadia or Ca. Jettenia. The highest copy number and the highest proportion of Planctomycetes were comparable to those of enriched anammox sludge. Thus, swine WWTPs that use activated sludge treatment can fortuitously acquire anammox biofilm. Thus, concentrated anammox can be detected by focusing on red biofilm.

Utilization of Bacillus sp. strain TAT105 as a biological additive to reduce ammonia emissions during composting of swine feces.

Bacillus sp. strain TAT105 is a thermophilic, ammonium-tolerant bacterium that grows assimilating ammonium nitrogen and reduces ammonia emission during composting of swine feces. To develop a practical use of TAT105, a dried solid culture of TAT105 (5.3 × 10(9) CFU/g of dry matter) was prepared as an additive. It could be stored for one year without significant reduction of TAT105. Laboratory-scale composting of swine feces was conducted by mixing the additive. When the additive, mixed with an equal weight of water one day before use, was added to obtain a TAT105 concentration of above 10(7) CFU/g of dry matter in the initial material, the ammonia concentration emitted was lower and nitrogen loss was approximately 22% lower in the treatment with the additive than in the control treatment without the additive. The colony formation on an agar medium containing high ammonium could be used for enumeration of TAT105 in the composted materials.

Effect of pH on phosphorus, copper, and zinc elution from swine wastewater activated sludge.

With the goal of reducing the amounts of phosphorus (P), copper (Cu), and zinc (Zn) discharged from swine wastewater activated sludge treatment facilities, we studied the elution of these elements from activated sludge at various pH values. Sludge samples with neutral pH collected from three farms were incubated at pH values ranging from 3 to 10. The soluble concentrations of these elements changed dramatically with pH and were highest at pH 3. We assumed that P present in the sludge under neutral and alkaline conditions was in insoluble form bound up with magnesium (Mg) and calcium (Ca), because Ca and Mg also eluted from the sludge at low pH. To clarify forms of Zn and Cu in the sludge, we performed a sequential extraction analysis. Zinc in adsorbed, organically bound, and sulfide fractions made up a large proportion of the total Zn. Copper in organically bound, carbonate, and sulfide fractions made up a large proportion of the total Cu. The soluble P concentrations were lowest at pH 9 or 10 (11-36 mg/L), the soluble Zn concentrations were lowest at pH 8 or 9 (0.07-0.15 mg/L), and the soluble Cu concentrations were lowest at pH 6-9 (0.2 mg/L, the detection limit).

Effect of electron donors on anammox coupling with nitrate reduction for removing nitrogen from nitrate and ammonium.

Anammox coupling with nitrate reduction under various electron donors was studied using sludge acclimatized to have anammox and denitrification activities. Due to a deficiency in electron donors for NO(3)(-) reduction, anammox activity in an inorganic medium containing NO(3)(-) and NH(4)(+) was lower than that in NO(2)(-) and NH(4)(+). Anammox could use NO(2)(-) competitively against denitrifiers under a very limited NO(2)(-) concentration, and additions of swine wastewater or acetate stimulated anammox activity in an inorganic medium containing NO(3)(-) and NH(4)(+) with no inhibition effects. However, a high concentration of swine wastewater caused an exponential increase in denitrification activity. The addition of hydrogen and iron stimulated anammox activity in an inorganic medium containing NO(3)(-) and NH(4)(+), but iron showed an inhibitory effect on anammox in a medium containing NO(2)(-) and NH(4)(+). Hydrogen was shown to be advantageous since it did not increase denitrification even when its addition was increased.

Effects of struvite formation and nitratation promotion on nitrogenous emissions such as NH3, N2O and NO during swine manure composting.

To reduce nitrogenous emissions from composting, two different countermeasures were applied simultaneously in swine manure composting. One was forming struvite by adding Mg and P at the start of composting, and the other was to promote nitratation (nitrite being oxidized nitrate) by adding nitrite-oxidizing bacteria after the thermophilic phase of composting. In the laboratory- and mid-scale composting experiments, 25-43% of NH3, 52-80% of N2O and 96-99% of NO emissions were reduced. From the nitrogen balance, it was revealed that the struvite formation reduced not only NH3, but also other nitrogenous emissions except N2O. The amount of total nitrogen losses was reduced by 60% by the two combined countermeasures, against 51% by the struvite formation alone. However, the nitratation promotion dissolved struvite crystals due to the pH decline, diminishing the effect of struvite as a slow-release fertilizer.

Distribution of phosphorus, copper and zinc in activated sludge treatment process of swine wastewater.

Changes in swine wastewater chemical features during an activated sludge treatment process were surveyed on 11 farms, and analyzed with non-biodegradable elements, i.e., phosphorus (P), copper (Cu), and zinc (Zn). In piggery wastewater, they were linearly correlated with suspended solid (SS) concentrations and the major portion was in solid fractions. After the pretreatment step, they were removed, with 80% for total P, 85% for total Cu, and 84% for total Zn. After the activated sludge process, total P, Cu, and Zn were then removed at 83%, 96%, and 95%, respectively. Removing SS thoroughly at each step was shown to be the most important factor in preventing outflow of these elements, since there are linear correlations or a positive relationship between the removal of SS concentrations and their removal in solid form. Most of the P, Cu, and Zn in activated sludge effluent was in soluble form, and the concentrations of Cu and Zn in the effluent were low enough, while further P removal might be required.

Characteristics of the microbial community associated with ammonia oxidation in a full-scale rockwool biofilter treating malodors from livestock manure composting.

The relationship between the activity and community structure of microbes associated with the oxidation of ammonia in a full-scale rockwool biofilter was examined by kinetic, denaturing gradient gel electrophoresis (DGGE), and sequence analyses. The packing materials were sampled from two different depths at 3 sites. Estimated K(m) values were similar among depths at same sampling sites, while V(max) differed in the mid-point sample. The lower depth of this site had the highest V(max). A correspondence analysis showed the DGGE profile of ammonia-oxidizing bacterial amoA of the lower depth of the mid-point sample to be distinguishable from the others. Banding patterns at other sites were similar among depths. Banding patterns of ammonia-oxidizing archaeal amoA of the mid-point sample were also similar among depths. The results suggested an association between the ammonia-oxidizing bacterial community's composition and ammonium oxidation kinetics in samples. Sequence analysis indicated that the ammonia-oxidizing bacterial community mainly belonged to the Nitrosomonas europaea lineage and Nitrosospira cluster 3. The ammonia-oxidizing archaeal amoA-like sequences were related to those belonging to soil and sediment groups, including one with 84% nucleotide similarity with Nitrosopumilus maritimus.

Evaluation of full-scale biofilter with rockwool mixture treating ammonia gas from livestock manure composting.

NH3 removal by a full-scale biofilter with rockwool packing materials was studied by measuring the gases and potential nitrification and denitrification activities of those materials in order to improve the biofiltration technology used in livestock farms. The rockwool biofilter was a durable and effective system for removing NH3, which was varied with the turning of manure composts. Furthermore, NH3 could be treated in the absence of an extra increase in two greenhouse gases, N2O and CH4. Potential nitrification and denitrification activities of the packing materials were estimated to be 8.2-12.2 mg N, and 1.42-4.69 mg N/100 g dry samples per day, respectively. The results suggested that potential nitrification and denitrification activities would increase within the biofilter where substrates, NH3 or NO3(-), have accumulated as a result of its operation. However, since percolate water contained high concentrations of NH4(+) and NO3(-), further improvement is required by reducing nitrogenous compounds within both the biofilter and percolate water.

Removal and recovery of phosphorous from swine wastewater by demonstration crystallization reactor and struvite accumulation device.

A demonstration crystallization reactor and struvite accumulation device for the removal and recovery of phosphorous was constructed and their performance was evaluated using actual swine wastewater for 3.5 years. The wastewater pH was increased by aeration, and the concentrations of total P and soluble PO(4)-P were reduced by a struvite crystallization reaction induced under a high pH condition. A 30% MgCl(2) addition was effective in enhancing the struvite crystallization reaction. The concentrations of suspended solids, total Zn and total Cu, were also decreased by the settling function of the reactor. On removing the efficiencies of these components, no noticeable seasonal fluctuation in performance was observed during the 3.5-year operation. In terms of maximum yield, 171g struvite was obtained from 1m(3) swine wastewater by the demonstration accumulation device for struvite recovery. The recovered struvite needed only air-drying before use since it was approximately 95% pure even without washing.

Reduction of nitrous oxide emission from pig manure composting by addition of nitrite-oxidizing bacteria.

Nitrous oxide (N2O) is emitted from pig manure composting, and the emission correlates with nitrite (NO2-) accumulation in the composting material. In the present study, we added nitrite-oxidizing bacteria (NOB)to inhibit NO2- accumulation and evaluated its effect on N2O emission in a laboratory-scale composting experiment. Mature pig manure compost (MPMC) containing NOB at 10(6) MPN g(-1) WM or cultured MPMC (cul-MPMC) NOB at 10(11) MPN g(-1) WM was added after the thermophilic phase of composting. The addition of these materials prevented NO2- accumulation, promoting oxidation to nitrate (NO3-), whereas the accumulation of NO2- occurred in the material to which NOB was not added as the result of the delayed growth of indigenous NOB compared with that of ammonia-oxidizing bacteria (AOB). The pattern of NO2- in the material agreed with that of N2O emission; therefore, N2O emission ceased rapidly when NOB was added. Emission rates of N2O were 88.5 (no addition), 17.5 (MPMC addition), and 20.2 (cul-MPMC addition) g N-N2O kg(-1) TNinitial, respectively. Improving composition of nitrifying communities for complete nitrification promotion would be useful to establish a composting method with low N2O emission.

Effect of addition of organic waste on reduction of Escherichia coli during cattle feces composting under high-moisture condition.

To ensure Escherichia coli reduction during cattle feces composting, co-composting with a variety of organic wastes was examined. A mixture of dairy cattle feces and shredded rice straw (control) was blended with organic wastes (tofu residue, rice bran, rapeseed meal, dried chicken feces, raw chicken feces, or garbage), and composted using a bench-scale composter under the high-moisture condition (78%). The addition of organic waste except chicken feces brought about maximum temperatures of more than 55 degrees C and significantly reduced the number of E. coli from 10(6) to below 10(2)CFU/g-wet after seven days composting, while in the control treatment, E. coli survived at the same level as that of raw feces. Enhancements of the thermophilic phase and E. coli reduction were related to the initial amount of easily digestible carbon in mass determined as BOD. BOD value more than 166.2 mg O2/DMg brought about significant E. coli reduction.

Recovery of phosphorous from swine wastewater through crystallization.

All the phosphate rock Japan needs must be presently imported from abroad because the country has no subterranean phosphorous resources. Therefore, there is a need to accelerate the development of and establish the technologies for phosphorous recovery from waste and wastewater. Swine wastewater has a high potential for phosphorous recovery in Japan. A reactor for removing and recovering phosphorous from swine wastewater was designed with dual functions, crystallization through aeration and separation of formed struvite by settling. However, a dehydration, composting and characterization process was first needed before using sediment sludge, including struvite, on farmland, since the struvite will settle along with huge amounts of other suspended solids (organic matter). For the recovery of pure struvite, an accumulation device was designed and its efficiency examined. The device has a struvite-accumulation face made of stainless steel wire mesh (1 mm in diameter, 1 cm(2) square) to reduce its total weight. During submergence in the aeration column of the demonstration reactor, struvite cross-bridged and accumulated on the face of the device. The struvite could be scraped off easily with only a light brushing, and was found to be approximately 95% pure. Because this device is a very simple structure, it is thought to be acceptable to swine farmers.

Isolation of thermophilic ammonium-tolerant bacterium and its application to reduce ammonia emission during composting of animal wastes.

A thermophilic bacterium, strain TAT105, was isolated from compost made of animal wastes. TAT105 had high tolerance to ammonium nitrogen up to 1200 mM, and highly assimilated nitrogen during the growth on swine feces. The strain was classified into Bacillus, close to Bacillus pallidus. To evaluate the effect of adding TAT105 to ammonia (NH3) emission during the composting process of animal wastes, laboratory scale composting was done. NH3 emission tended to be lower and nitrogen loss was smaller in the TAT105-added material than in the control material to which TAT105 was not added. Thermophilic ammonium-tolerant bacteria in the TAT105-added material increased to about 8x10(9) CFU/g of dry matter on the average during the tests, and most of them were judged to be TAT105 from morphological colony discrimination. These results suggested the possibility of reducing NH3 emission from composting of animal wastes by adding TAT105.

Patterns and quantities of NH(3), N(2)O and CH(4) emissions during swine manure composting without forced aeration--effect of compost pile scale.

To evaluate the NH(3), N(2)O, and CH(4) emissions from composting of livestock waste without forced aeration in turned piles, and to investigate the possible relationship between the scale of the compost pile and gas emission rates, we conducted swine manure composting experiments in parallel on small- and large-scale compost piles. Continuous measurements of gas emissions during composting were carried out using a chamber system, and detailed gas emission patterns were obtained. The total amount of each gas emission was computed from the amount of ventilation and gas concentration. NH(3) emission was observed in the early period of composting when the material was at a high temperature. Sharp peaks in CH(4) emission occurred immediately after swine manure was piled up, although a high emissions level continued after the first turning only in the large-scale pile. N(2)O emissions started around the middle stage of the composting period when NH(3) emissions and the temperature of the compost material began to decline. The emission rates of each gas in the small and large piles were 112.8 and 127.4 g NH(3)-N/kg T-N, 37.2 and 46.5 g N(2)O-N/kg T-N, and 1.0 and 1.9 g CH(4)/kg OM, respectively. It was found that changing the piling scale of the compost material was a major factor in gas emission rates.