Comparison of Nitrogen Removal and Full-Scale Wastewater Treatment Plant Characteristics in Thailand and Japan

Four full-scale systems wastewater treatment plants (WWTPs) were used as study sites. All of these WWTPs were designed and operated for biological nitrogen removal (BNR) by using nitrification-denitrification processes. In general, the WWTPs in Thailand operated at higher values of temperature, HRT and SRT. Influents and effluents from these sites are compared and discussed in terms of BNR, dominant nitrifying microorganisms and WWTP design. Nitrogen removal was observed in all the sites and correlated to the influent total N to BOD ratio. Polymerase chain reaction coupled with denaturing gradient gel electrophoresis was used to identify dominant bacteria involved in nitrogen transformations: ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB), and nitrate reducing bacteria (NRB). AOB Nitrosomonas sp. was found only in Thailand where aerobic HRT was ≥ 4 hours and SRT was ≥15 days. Furthermore, AOB Nitrosospira sp. were found only in Japan at aerobic HRT ≤ 4 hours and SRT≤ 13 temperature (21-27°C). NOB Nitrospira sp. was found at aerobic HRT ≥ 4 hours and SRT ≥ 6 days. Interestingly, Nitrotoga sp. was found in the aerobic tank one in Thailand and one in Japan and co-occurred with NRB Burkholderia denitrificans. The higher wastewater temperature and lower influent nitrogen concentration in Thailand appear to promote a different AOB and NOB community structure than in Japan. The most important factor affecting TN removal was the influent TN to BOD ratio

Nutrient Removal Performance on Domestic Wastewater Treatment Plants (Full Scale System) between Tropical Humid and Cold Climates

Two full scale systems of oxidation ditches for domestic wastewater treatment plants (WWTP) were used as study sites: Phuket Province, southern Thailand (representative of tropical humid climates) and Plum Creek, Castle Rock, Colorado, USA (representative of cold climates). The treatment systems at both sites were designed for biological nutrient removal (BNR) from extended activated sludge. Nitrogen is removed by nitrification-denitrification processes. The solid retention time (SRT) for both treatment plants was ≥ 10 d as recommended by theory for complete nitrification in activated sludge wastewater treatment plants. Influents and effluents from these sites were compared in respect to flow rate, biochemical oxygen demand (BOD), organic nitrogen, ammonium, nitrate, total nitrogen, and phosphorus concentrations. At both sites, nutrient removal reached more than 75 % because there was sufficient carbon for denitrifying and phosphate accumulating organisms. Furthermore, low dissolved oxygen concentration, long SRT, and high temperature could be key factors to promote activity of some groups of bacteria in consuming organic matter and nutrients in wastewater in warm climates. For this reason, plant design and operating procedures for wastewater treatment in cold climates might not be always be applicable to warm climates

Nitrogen Removal Efficiency at Centralized Domestic Wastewater Treatment Plants in Bangkok, Thailand

In this study, influents and effluents from centralized domestic wastewater treatment systems in Bangkok (Rattanakosin, Dindaeng, Chongnonsi, Nongkhaem, and Jatujak) were randomly collected in order to measure organic nitrogen plus ammonium-nitrogen (total Kjeldahl nitrogen), total organic carbon, total suspended solids, and total volatile suspended solids by using Standard Methods for the Examination of Water and Wastewater 1998. Characteristics of influent and effluent (primary data) of the centralized domestic wastewater treatment system from the Drainage and Sewerage Department of Bangkok Metropolitan Administration were used to analyze efficiency of systems. Fluorescent in situ hybridization (FISH) was used to identify specific nitrifying bacteria (ammonium oxidizing bacteria specific for Nitrosomonas spp. and nitrite oxidizing bacteria specific for Nitrobacter spp. and Nitrospira spp.). Although Nitrosomonas spp. and Nitrobacter spp. were found, Nitrospira spp. was most prevalent in the aeration tank of centralized wastewater treatment systems. Almost all of the centralized domestic wastewater treatment plants in Bangkok are designed for activated sludge type biological nutrient removal (BNR). However, low efficiency nitrogen removal was found at centralized wastewater treatment plants in Bangkok. Influent ratio of TOC:N at centralized treatment plant is less than 2.5. Centralized wastewater treatment systems have not always been used suitability and used successfully in some areas of Bangkok Thailand

Mixing Intensity Effects of Attached Growth on Enriched Anammox Cultures

Anaerobic ammonium oxidation (anammox) is a promising new technology for the treatment of wastewater with high ammonium and low carbon concentrations. Earlier work suggests that optimal processing would be realized within a sequencing batch reactor (SBR). However, the relatively slow growth of anammox bacteria inhibits the rates of nitrogen removal and biomass yielding. Improved anammox performance has been demonstrated when the bacteria are in granular form or attached to a growth medium. Little has been reported concerning the effect of mixing rate on nitrogen (N) removal with attached anammox bacteria. This work subjected anammox bacteria attached to polystyrene sponge in SBR to various intensities of impeller mixing and studied the effect on NH4+ and NO2- removal. Nitrogen processing was virtually the same with velocity gradient values between 13.5 and 222 s-1. More vigorous mixing at 407 and 666 s-1 values significantly inhibited N removal, likely due to detachment of bacteria from the growth medium. Following the poor N removal at the two higher mixing intensities, agitation was reduced to 24.8 s-1 velocity gradient value. Recovery of N removal rates required 2-3 weeks, the slow time attributed to slow reattachment to the growth medium. Denaturing gradient gel electrophoresis (DGGE) analysis identified the prominent anammox species in the experimental study as Candidatus Brocadia anammoxidans and Candidatus Kuenenia stuttgartiensis

Efficacies of Nitrogen Removal and Comparisons of Microbial Communities in Full-Scale (Pre-Anoxic Systems) Municipal Water Resource Recovery Facilities at Low and High COD:TN Ratios

At a low COD:TN ratio (≤5) in influent, maintaining a longer HRT (≥9 h) and longer SRT (≥30 d) are suggested to improve higher N removal efficiency in case of operation at low DO (Dissolved oxygen) level (0.9 ± 0.2 mg-O2/L). However, in case of operation at high DO level (4.0 ± 0.5 mg-O2/L), short HRT (1 h) and typical SRT (17 d) make it possible to achieve nitrogen removal. On the other hand, at a high COD:TN ratio (≥8.4), a typical HRT (9–15 h), SRT (12–19 d), and DO level (1.3–2.6 mg-O2/L) would be applied. Microbial distribution analysis showed an abundance of AOA (Ammonia-oxidizing archaea) under conditions of low DO (≤0.9 mg-O2/L). Nitrosomonas sp. are mostly found in the all investigated water resource recovery facilities (WRRFs). Nitrosospira sp. are only found under operating conditions of longer SRT for WRRFs with a low COD:TN ratio. In comparison between abundances of Nitrobacter sp. and Nitrospira sp., abundances of Nitrobacter sp. are proportional to low DO concentration rather than abundance of Nitrospira sp. A predominance of nosZ-type denitrifiers were found at low DO level. Abundance of denitrifiers by using nirS genes showed an over-abundance of denitrifiers by using nirK genes at low and high COD:TN ratios

Efficacies of Nitrogen Removal and Comparisons of Microbial Communities in Full-Scale (Pre-Anoxic Systems) Municipal Water Resource Recovery Facilities at Low and High COD:TN Ratios

At a low COD:TN ratio (≤5) in influent, maintaining a longer HRT (≥9 h) and longer SRT (≥30 d) are suggested to improve higher N removal efficiency in case of operation at low DO (Dissolved oxygen) level (0.9 ± 0.2 mg-O2/L). However, in case of operation at high DO level (4.0 ± 0.5 mg-O2/L), short HRT (1 h) and typical SRT (17 d) make it possible to achieve nitrogen removal. On the other hand, at a high COD:TN ratio (≥8.4), a typical HRT (9–15 h), SRT (12–19 d), and DO level (1.3–2.6 mg-O2/L) would be applied. Microbial distribution analysis showed an abundance of AOA (Ammonia-oxidizing archaea) under conditions of low DO (≤0.9 mg-O2/L). Nitrosomonas sp. are mostly found in the all investigated water resource recovery facilities (WRRFs). Nitrosospira sp. are only found under operating conditions of longer SRT for WRRFs with a low COD:TN ratio. In comparison between abundances of Nitrobacter sp. and Nitrospira sp., abundances of Nitrobacter sp. are proportional to low DO concentration rather than abundance of Nitrospira sp. A predominance of nosZ-type denitrifiers were found at low DO level. Abundance of denitrifiers by using nirS genes showed an over-abundance of denitrifiers by using nirK genes at low and high COD:TN ratios

Dissolution of aluminum hydroxide to provide Al and to neutralize acidity for the removal and recovery of fluoride through cryolite crystallization

Dissolution of aluminum hydroxide (Al(OH)3(s)) was investigated for providing Al and at the same time neutralizing the acidity generated in the recovery of fluoride through the crystallization of cryolite. The alka-linity provided by the dissolution of Al(OH)3(s) combined with Na2CO3 reduces the total treatment cost for fluoride recovery by 45%, compared to when other aluminum salts were used. In this study, two types of aluminum hydroxide having different degrees of crystallinity of 61.53% and 25.57%, denoted as crystalline Al (OH)3(s) (CAH) and amorphous Al(OH)3(s) (AAH), respectively, were investigated. The results showed that the dissolution of AAH was very efficient but an excess amount of AAH adsorbed the freshly formed AlF3 complexes, impairing the purity of cryolite. On the other hand, the dissolution of the CAH was mostly dependent on the time, the Al dosage, and the initial pH of the solution. Upon reaching equilibrium, the dissolved Al to the initial F molar ratio reached 2/6. With the mixed volume ratio of 1:1 between the raw HF solution and the HF solution being equilibrated with CAH initially, the removal of F reached 96% and the cryolite formation was positively confirmed based on the XRD analysis of the resulting solid