Decomposition of rice straw residues and the emission of CO2, CH4 under paddy rice and crop rotation in the Vietnamese Mekong Delta region – A microcosm study

This study investigated the influence of soil undergoing different crop rotations on the CH₄, CO₂ emissions, and decomposition of rice straw. The studied soil undergoing crop rotation systems were rice-rice-rice (SR) and baby corn-rice-mungbean (SB). Two main microcosm set-ups: anaerobic (SR-AN, SB-AN) and aerobic (SR-AE, SB-AE) conditions. Litter bags containing rice stems were inserted into the soil and recollected at different time points for chemical analysing and the gas sampling was collected to measure the CO₂ and CH₄ emissions. The results indicated that the total carbon (TC) decreased around 30%, and the TC removal in anaerobic was significantly higher than in aerobic conditions. The residue cellulose content varied in a range from 68.2% to 78.6%, while the hemicellulose content varied from 57.4% to 69.3% at day 50 after incorporation. There were no significant differences in the total nitrogen removal, cellulose, hemicellulose, and lignin contents among the microcosm set-ups. CO₂ emission increased in all the microcosm set-ups with the treatments without rice straw (CTSR, CTSB) in both aerobic and anaerobic conditions. CH₄ release in the SR-AN treatments did not differ significantly compared with the SB-AN treatments. This study confirmed that the decomposition of rice straw residues is faster in the anaerobic paddy soil condition compared to the aerobic crop rotation condition.

Integration of anammox into the MBR process for main stream sewage treatment

The integration of Anaerobic ammonia oxidation (anammox) into the membrane bioreactor (MBR) process (AX-MBR) is proposed in this study to reduce operating costs. The temperature was not controlled during the study. Anammox, denitrification, and nitrification were studied in the AX-MBR for 210 days. The reactor was fed with mainstream sewage from Guilin City, China. The results showed that AX-MBR could run with reduced dissolved oxygen (DO) concentration, and COD, NH4+-N, and total nitrogen removal were maintained or improved. The microbial analysis results demonstrated that the added anammox sludge could survive in the AX-MBR, but the sludge microbial diversity decreased. Nitrospira, Candidatus Kuenenia, and Nitrosomonas dominated the anammox sludge. In a word, the AX-MBR developed in this study could treat mainstream sewage with the appropriate management, and the operation costs are expected to reduce by decreasing the amount of aeration.

Pengaruh Sistem Aerasi Intermittent terhadap Removal Organik dan Nitrogen pada Pengolahan Air Limbah Domestik Kamar Mandi Umum

Sebuah instalasi pengolahan air limbah (IPAL) dibangun untuk mengolah air limbah greywater dan blackwater dari toilet dan kamar mandi umum Wisdom Park UGM yang terletak di Dusun Kuningan, Catur Tunggal, Sleman, Daerah Istimewa Yogyakarta. Unit reaktor proses IPAL tersebut terdiri dari sedimentasi, ekualisasi, aerasi 1, aerasi 2 dan secondary clarifier dengan sistem pengolahan berupa aerasi intermitten dan aerasi kontinyu dengan menggunakan Microbubble Generator (MBG) dan blower. Saat ini belum pernah dilakukan kajian terkait efektivitas sistem proses biologi pada IPAL dalam menurunkan kandungan organik dan nitrogen air limbah. Suatu sistem aerasi intermitten diaplikasikan dengan tujuan untuk mendegradasi kandungan organik dan nitrogen yang terkandung dalam air limbah, juga dapat meningkatkan dan meratakan suplai oksigen sehingga kemampuan penyerapan oksigen menjadi lebih besar. Evaluasi IPAL dilakukan selama 82 hari pengamatan dengan parameter air limbah yang diujikan terdiri dari COD, NH3-N, NO3-N, NO2-N, dan PO4-P yang nantinya akan dibandingkan dengan PerMenLHK No 68 Tahun 2016 tentang Baku Mutu Air Limbah Domestik. Hasil performa removal kontaminan di tangki aerasi 1 dan tangki aerasi 2 tidak jauh berbeda, sehingga menunjukkan bahwa pengolahan di tangki aerasi 2 tidak begitu efektif. Pada tangki aerasi 1 rerata removal COD sebesar 73,97±17,65%, removal PO4-P sebesar 53,31±13,72%, removal total nitrogen sebesar 1,57±164,29%, efisiensi nitrifikasi sebesar 82,26±16,47% dan efisiensi denitrifikasi sebesar -66,4±373,37%. Sedangkan, total konsumsi energi yang dibutuhkan untuk pengolahan air limbah di IPAL dengan debit rerata 82,06 l/hari sebesar 43,13 kWh/m3 dan biaya sebesar Rp 62.326,00/m3. Dengan konsumsi energi terbesar dihasilkan untuk peyisihan fosfat yaitu 2,99 kWh/gPO4-P, penyisihan total nitrogen sebesar 1,33 kWh/gTN, penyisihan ammonia sebesar 0,88 kWh/gNH3-N, dan penyisihan COD sebesar 0,7 kWh/gCOD. ABSTRACTA wastewater treatment plant (WWTP) was built to treat greywater and blackwater from the public toilets and bathrooms of Wisdom Park UGM located in Dusun Kuningan, Catur Tunggal, Sleman, Special Region of Yogyakarta. The WWTP process reactor unit consists of sedimentation, equalization, aeration 1, aeration 2 and secondary clarifier with a processing system in the form of intermittent aeration and continuous aeration using a Microbubble Generator (MBG) and a blower. Currently, no study has been conducted regarding the effectiveness of the biological process system in WWTPs in reducing the organic and nitrogen content of wastewater. An intermittent aeration system is applied with the aim of degrading organic and nitrogen content contained in wastewater, as well as increasing and leveling oxygen supply so that oxygen absorption capacity becomes greater. The WWTP evaluation was carried out for 82 days of observation with the tested wastewater parameters consisting of COD, NH3-N, NO3-N, NO2-N, and PO4-P which will later be compared with the Minister of Environment and Forestry's Regulation No. 68, 2016 on Domestic Wastewater Quality Standards. The results of the contaminant removal performance in aeration tank 1 and aeration tank 2 were not much different, indicating that the treatment in aeration tank 2 was not very effective. In aeration tank 1 the mean COD removal was 73,97±17,65%, PO4-P removal was 53,31±13,72%, total nitrogen removal was 1,57±164,29%, nitrification efficiency was 82,26±16,47%, and denitrification efficiency was -66,4±373,37% in aeration tank 1. Meanwhile, the total energy consumption required for wastewater treatment at WWTP with an average discharge 82.06 l/day is 43.13 kWh/m3 and a cost of Rp. 62,326.00/m3. Phosphate removal required the most energy, at 2.99 kWh/gPO4-P, followed by total nitrogen removal at 1.33 kWh/gTN, ammonia removal at 0.88 kWh/gNH3-N, and COD removal at 0.7 kWh/gCOD

The main anammox-based processes, the involved microbes and the novel process concept from the application perspective

Anammox technology has been widely researched over the past 40-year from the laboratory-scale to full-scale. It is well-known that in actual applications, the solo application of anammox is not feasible. Since both ammonium and nitrite are prerequisites based on the reaction mechanism, the pre-treatment of wastewater is necessary. With the combination of anammox process and other pre-treatment processes to treat the actual wastewater, many types of anammox-based processes have been developed with distinct nitrogen removal performance. Thus, in order to heighten the awareness of researchers to the developments and accelerate the application of these processes to the treatment of actual wastewater, the main anammox-based processes are reviewed in this paper. It includes the partial nitritation/anammox process, the denitratation/anammox (PD/A) process, the denitrifying anaerobic methane oxidation/anammox (DAMO/A) process, and more complex deuterogenic processes. These processes have made the breakthroughs in the application of the anammox technology, such as the combination of nitrification and PD/A process can achieve stability and reliability of nitrogen removal in the treatment of mainstream wastewater, the PD/A process and the DAMO/A have brought about further improvements in the total nitrogen removal efficiency of wastewater. The diversity of functional microbe characteristics under the specific condition indicate the wide application potential of anammox-based processes, and further exploration is necessary. A whole waste treatment system concept is proposed through the effective allocation of above mentioned processes, with the maximum recovery of energy and resources, and minimal environmental impact.

The Influence of Different Operation Conditions on the Treatment of Mariculture Wastewater by the Combined System of Anoxic Filter and Membrane Bioreactor

The mariculture wastewater treatment performance for the combined system of anoxic filter and membrane bioreactor (AF-MBR) was investigated under different hydraulic retention times (HRTs), influent alkalinity, and influent ammonia nitrogen load. The results showed that the removal efficiencies of TOC and total nitrogen were slightly better at the HRT of 8 h than at other HRTs, and the phosphate removal efficiency decreased with the increase of HRT. With the increase of influent alkalinity, the removal of TOC and phosphate did not change significantly. With the increase of influent alkalinity from 300 mg/L to 500 mg/L, the total nitrogen removal efficiency of AF-MBR was improved, but the change of the removal efficiency was not obvious when the alkalinity increased from 500 mg/L to 600 mg/L. When the influent concentration of ammonia nitrogen varied from 20 mg/L to 50 mg/L, the removal efficiencies of TOC, phosphate, and total nitrogen by AF-MBR were stable. An interesting finding was that in all the different operation conditions examined, the treatment efficiency of AF-MBR was always better than that of the control MBR. The concentrations of NO3−-N in AF-MBR were relatively low, whereas NO3−-N accumulated in the control MBR. The reason was that the microorganisms attached to the carrier and remained fixed in the aerobic and anoxic spaces, so that there was a gradual enrichment of bacteria characterized by slow growth in a high-salt environment. In addition, the microorganisms could gather and grow on the carrier forming a biofilm with higher activity, a richer and more stable population, and enhanced ability to resist a load impact.

Modeling granule-based completely autotrophic nitrogen removal over the nitrite (CANON) process in an SBR

Based on the simplified activated sludge model No. 1 (ASM1), a 1D biofilm model containing autotrophic microorganisms and heterotrophic microorganisms was developed to describe the microbial population dynamics and reactor dynamics of CANON SBR. After sensitivity analysis and calibration for parameters, the simulation results of NH4+-N concentration and NO2−-N concentration were consistent with the measured results, while the simulated NO3−-N concentration was slightly lower than the measured. The simulation results showed that the soluble microbial products had an extremely low concentration. The aerobic ammonia oxidation bacteria and anaerobic ammonia oxidation bacteria were the dominant microbial populations of the CANON system, while nitrite oxidization bacteria and heterotrophic bacteria were eliminated completely. The optimal ratio of air aeration load to influent NH4+-N load was about 0.18 L air/mgN. The operation condition of the reactor was optimized according to the simulation results, and the total nitrogen removal rate and the total nitrogen removal efficiency increased from 0.312 ± 0.015 to 0.485 ± 0.013 kg N/m3/d and from 71.2 ± 4.3 to 85.7 ± 1.4%, respectively.

Evaluation of biological nutrient removal by anammox in three phase fluidized bed bioreator

The purpose of this study was to show the viability of a 0.70 m3 three phase aerobic fluidized bed bioreactor for the denitrification of wastewater by anammox bacteria. The reactor was monitored for 343 days, operating in a batch mode for 50 days, with a continuous flow of wastewater being fed for the remaining 293 days. It was determined that anammox contributed up to 5.5±0.5% of the ammonia removal during the batch mode of operation, and up to 14.2±3.7% of the ammonia removal during the continuous mode of operation. The highest ammonia and total nitrogen removals of 90.9±1.6% and 20.8±4.1% were measured under high recycle rates. Up to 63.1±5.2% and 19.2±7.5% ammonia and total nitrogen removal was observed after a single pass through the reactor. At low COD concentrations and anoxic conditions, ammonia and nitrite were removed simultaneously. Under the evaluated conditions, the reactor was determined to contain anammox bacteria.

Evaluation of biological nutrient removal by anammox in three phase fluidized bed bioreator

The purpose of this study was to show the viability of a 0.70 m3 three phase aerobic fluidized bed bioreactor for the denitrification of wastewater by anammox bacteria. The reactor was monitored for 343 days, operating in a batch mode for 50 days, with a continuous flow of wastewater being fed for the remaining 293 days. It was determined that anammox contributed up to 5.5±0.5% of the ammonia removal during the batch mode of operation, and up to 14.2±3.7% of the ammonia removal during the continuous mode of operation. The highest ammonia and total nitrogen removals of 90.9±1.6% and 20.8±4.1% were measured under high recycle rates. Up to 63.1±5.2% and 19.2±7.5% ammonia and total nitrogen removal was observed after a single pass through the reactor. At low COD concentrations and anoxic conditions, ammonia and nitrite were removed simultaneously. Under the evaluated conditions, the reactor was determined to contain anammox bacteria.