Risk factors for vertebral compression fractures in preoperative chemoradiotherapy with gemcitabine for pancreatic cancer

BACKGROUND AND PURPOSE

Preoperative chemoradiotherapy (CRT) with gemcitabine (GEM) for pancreatic cancer is often accompanied by vertebral compression fractures (VCFs). This study aimed to establish the incidence of VCFs and identify the related risk factors (RFs) to elucidate how to decrease the overall incidence of VCF.

MATERIAL AND METHODS

We investigated 220 patients with resectable or borderline-resectable pancreatic cancers who had completed preoperative CRT between 2006 and 2011. The RFs associated with VCF were analyzed in a total of 1308 thoracolumbar vertebral bodies.

RESULTS

Thirty-seven VCFs occurred in 25 patients (11%); the cumulative incidence at two years was 18.9%. Univariate analysis revealed female sex, age and high daily GEM concentration during radiotherapy as RFs for VCF. The multivariate mixed effects logistic regression model demonstrated that the most responsible factor was radiation dose (p<0.001). We estimated the radiation condition resulting in a fracture incidence of ⩽5% by counting the patient's number of the three RFs. For patients with three factors, the mean vertebral dose was 22.0 Gy.

CONCLUSIONS

The RFs for VCF after CRT were identified. The side effect of VCF might be avoided by regulating the radiation dose to neighboring vertebral bodies after considering the RFs.

Validation of the Japanese version of the Systemic Lupus Activity Questionnaire that includes physician-based assessments in a large observational cohort

The Systemic Lupus Activity Questionnaire (SLAQ) is a patient-reported outcome for systemic lupus erythematosus (SLE). We aimed to translate it into Japanese and further investigate its validity and reliability. The English version of the SLAQ was translated into Japanese and administered to Japanese SLE patients at our university clinic. Physicians assessed disease activity using the SLE Disease Activity Index 2000 (SLEDAI-2K). The patients were prospectively followed for repeat assessment a year later. Ultimately, 255 patients participated. The patients’ 10-point ratings of disease activity and SLAQ scores were significantly correlated (Spearman’s ρ = 0.53). The SLAQ score was weakly correlated with the SLE Disease Activity Index 2000 (SLEDAI-2K)-nolab (omitting laboratory items; ρ = 0.18) but not with the SLEDAI-2K ( ρ = 0.02). These results suggested its convergent and discriminant validity. The SLAQ demonstrated acceptable internal consistency (Cronbach’s α = 0.80), and good test–retest reliability (intraclass correlation coefficient = 0.85). The effect sizes and the standardized response means of the SLAQ were as follows: clinical worsening, 0.26 and 0.31, and improvement, −0.39 and −0.41, respectively, which indicated a small but significant responsiveness. The Japanese version of the SLAQ demonstrated acceptable reliability and validity; its performance was comparable to that of the original version.

Psychological distress in corticosteroid-naive patients with systemic lupus erythematosus: A prospective cross-sectional study

OBJECTIVE

Psychological distress, such as depression and anxiety, has been intensively studied in patients with systemic lupus erythematosus (SLE). However, those studies have mostly included patients who were treated with corticosteroids, which might themselves induce mood disturbances. We investigated psychological distress in corticosteroid-naive patients with SLE who did not exhibit any overt neuropsychiatric manifestations.

METHODS

Forty-three SLE in-patients with no current or past abnormal neuropsychiatric history participated in the study. Patients and 30 healthy control subjects with similar demographic and personality characteristics were administered a comprehensive battery of psychological/neuropsychological tests. The Profile of Mood States (POMS) was used to assess depression and anxiety. Results of clinical, laboratory, and neurological tests were compared with regard to their presence.

RESULTS

Prevalence of depression was higher in patients (n = 11, 25.6%) than in controls (n = 2, 6.7%; p = 0.035), although prevalence of anxiety did not differ across groups (patients: 34.9%, n = 15; controls: 16.7%, n = 5; p = 0.147). Using multiple logistic regression analysis, we identified avoidance coping methods (OR, 1.3; 95% CI 1.030-1.644; p = 0.027) as an independent risk factor for depression.

CONCLUSION

Our results indicate that depression presents more frequently in corticosteroid-naive patients with early-stage, active SLE than in the normal population, but anxiety does not. Depression may be related to psychological reactions to suffering from the disease.

Selective neck irradiation for supraglottic cancer: focus on Sublevel IIb omission

OBJECTIVE

To estimate selective neck irradiation omitting surgical Sublevel IIb.

METHODS

Bilateral necks of 47 patients (94 necks) were subjected to definitive radiotherapy for supraglottic cancer. Sixty-nine and 25 necks were clinically node negative (cN-) and clinically node positive (cN+), respectively. We subdivided Sublevel IIb by the international consensus guideline for radiotherapy into Sublevel IIb/a, directly posterior to the internal jugular vein, and Sublevel IIb/b, which was behind Sublevel IIb/a and coincided with surgical Sublevel IIb. Bilateral (Sub)levels IIa, III, IV and IIb/a were routinely irradiated, whereas Sublevel IIb/b was omitted from the elective clinical target volume in 73/94 treated necks (78%).

RESULTS

Two patients presented with ipsilateral Sublevel IIb/a metastases. No Sublevel IIb/b metastasis was observed. Five patients experienced cervical lymph node recurrence; Sublevel IIb/a recurrence developed in two patients, whereas no Sublevel IIb/b recurrence occurred even in the cN- necks of cN+ patients or cN0 patients. The 5-year regional control rates were 91.5% for Sublevel IIb/b-omitted patients and 77.8% for Sublevel IIb/b treated patients.

CONCLUSIONS

Selective neck irradiation omitting Sublevel IIb/b did not compromise regional control and could be indicated for cN- neck of supraglottic cancer.

Association of oral health literacy with oral health behaviour and oral health status in Belarus

OBJECTIVES

To explore the level of oral health literacy among adults in Belarus, a former part of the Soviet Union, and to analyse the associations between oral health literacy, socio-demographics, health behaviour and oral health status.

BASIC RESEARCH DESIGN

A cross-sectional study. Participants: 281 adult (18-60 years old) dental patients.

MAIN OUTCOME MEASURE

The participants completed a self-administered questionnaire collecting information about socio-demographics and health behaviours, and oral health literacy test (the R-OHLI). Clinical oral examination followed the questionnaire survey.

RESULTS

Among participants, 68.7% had adequate, 18.9% had marginal and 12.4% inadequate oral health literacy levels. Females and those with higher education were more likely to have adequate oral health literacy (p<0.05 and p<0.001). Participants with adequate oral health literacy had fewer missing and more filled teeth than those with inadequate literacy (p<0.001). This association remained significant after adjusting for socio-demographics, behavioural characteristics and oral hygiene status (p<0.05 and p<0.001).

CONCLUSIONS

Adequate oral health literacy was strongly related with better oral health status. Improvement of oral health literacy should be addressed when developing community oral health promotions.

Plasma levels of vitamin D metabolites in renal diseases

Plasma levels of 25-OH-D, 1,25-(OH)2-D and 24,25-(OH)2-D in acute renal failure, chronic glomerulonephritis and chronic renal failure were determined by competitive protein binding assay and evaluated for the correlation with the degree of renal impairment and the influence of dialysis, renal transplantation and the administration of vitamin D and 1-alpha-OH-D3. In this study it is revealed that 25-OH-D deficiency could be normalized by the administration of vitamin D2. Plasma levels of 1,25-(OH)2-D are decreased in proportion to the degree of renal impairment and it is clearly depressed in patients, with a Ccr of 30 ml/min or less. Although biosynthesis of 24,25-(OH)2-D is not remarkably depressed, it is necessary to resolve various questions including the methods of measurement in this respect. It is also disclosed in the present study that 1-alpha-OH-D3 is faster in action than vitamin D2 when used to correct 1,25-(OH)2-D3 deficiency.

Learning curve for laparoscopic major hepatectomy

BACKGROUND

Laparoscopic major hepatectomy (LMH) is evolving as an important surgical approach in hepatopancreatobiliary surgery. The present study aimed to evaluate the learning curve for LMH at a single centre.

METHODS

Data for all patients undergoing LMH between January 1998 and September 2013 were recorded in a prospective database and analysed. The learning curve for operating time (OT) was evaluated using the cumulative sum (CUSUM) method.

RESULTS

Of 173 patients undergoing major hepatectomy, left hepatectomy was performed in 28 (16·2 per cent), left trisectionectomy in nine (5·2 per cent), right hepatectomy in 115 (66·5 per cent), right trisectionectomy in 13 (7·5 per cent) and central hepatectomy in eight (4·6 per cent). Median duration of surgery was 270 (range 100-540) min and median blood loss was 300 (10-4500) ml. There were 20 conversions to an open procedure (11·6 per cent). Vascular clamping was independently associated with conversion on multivariable analysis (hazard ratio 5·95, 95 per cent c.i. 1·24 to 28·56; P = 0·026). The CUSUMOT learning curve was modelled as a parabola (CUSUMOT  = 0·2149 × patient number(2)  - 30·586 × patient number - 1118·3; R(2)  = 0·7356). The learning curve comprised three phases: phase 1 (45 initial patients), phase 2 (30 intermediate patients) and phase 3 (the subsequent 98 patients). Although right hepatectomy was most common in phase 1, a significant decrease was observed from phase 1 to 3 (P = 0·007) in favour of more complex procedures.

CONCLUSION

The learning curve for LMH consisted of three characteristic phases identified by CUSUM analysis. The data suggest that the learning phase of LMH included 45 to 75 patients.

Treatment outcomes of external-beam radiotherapy for squamous cell carcinoma of the base of the tongue

PURPOSE

To evaluate definitive external-beam radiotherapy (EBRT) for patients with base of the tongue (BOT) cancers.

METHODS

We reviewed results for 26 patients with BOT cancers who were treated with EBRT. Clinical stages T1, T2, T3, and T4a were observed for 10, 7, 4, and 5 patients, respectively, and stages N0, N1, N2a, N2b, N2c, and N3 were observed for 4, 2, 5, 6, 8, and 1 patients, respectively. More than half of the patients (n = 19) were stage IVA. Standard total delivered doses were 70 Gy to primary tumors and cervical lymph node (CLN) metastases and 40-46 Gy to elective nodal regions. Eleven patients with advanced loco-regional disease received concurrent or neoadjuvant chemotherapy. Four T3 patients and one T2 patient received 2 or 3 cycles of concurrent intra-arterial cisplatin with EBRT (RADPLAT).

RESULTS

Three-year overall survival was 69 % (95 % CI 47-83 %), with a median follow-up period of 33 months. Three-year local control was 100, 86, 100, and 20 % for T1, T2, T3, and T4 patients, respectively. Three-year regional control was 100 % for N0, N1, and N2a, 83 % for N2b, 75 % for N2c, and 0 % for N3 patients. Treatment failed for 7 patients. All 5 patients undergoing RADPLAT achieved complete responses and did not develop local recurrence.

CONCLUSIONS

We achieved favorable outcomes for patients with T1-T3 BOT cancers by use of definitive EBRT with or without chemotherapy.

Histopathological effects of preoperative chemoradiotherapy for pancreatic cancer: an analysis for the impact of radiation and gemcitabine doses

BACKGROUND AND PURPOSE

Histopathological findings of patients who underwent resection for pancreatic adenocarcinoma (PC) after preoperative chemoradiotherapy (CRT) reportedly showed beneficial effects. The purpose of our study was to evaluate the correlation between histopathological effects (HE) of preoperative CRT and treatment parameters [radiation and gemcitabine (GEM) doses].

MATERIAL AND METHODS

HE of CRT were assessed on 158 primary lesions of 157 patients with PC who underwent pancreatic resection after preoperative CRT with GEM between January 2006 and December 2011. The radiation dose delivered to the primary tumor site and surrounding regional nodal areas was 50 Gy until September 2009 followed by the dose escalation of a 10 Gy boost added for delivery with the field-in-field technique to the roots of the celiac and superior mesenteric arteries. Intravenous administration of GEM (1000 /m(2)) was initiated concurrently on days 1, 8, and 15, every 4 weeks and generally repeated for 3 cycles. HE of CRT on the primary tumor were categorized based on the number of tumor cells destroyed.

RESULTS

The median overall survival time was 74.5 months and 3-year and 5-year survival rates were 64.3% and 54.5%, respectively. Dose-volume parameters of radiation such as D33 with a cut-off value of 51.6 Gy were correlated significantly with HE (p=.0230). Lesions having received GEM>7625 mg/m(2) before surgical resection more frequently showed positive HE (p=.0002). Multivariate logistic regression analysis demonstrated that both D33 and cumulative GEM dose were significant predictors of definite HE (p=.0110 and <.0001, respectively).

CONCLUSIONS

Our retrospective analysis showed that dose intensity of radiation and GEM is significantly related to HE of preoperative CRT for PC.

The Composition Pulling Effect in MOVPE Grown InGaN on GaN and AlGaN and its TEM Characterization

InGaN films have been grown on GaN and AlGaN epitaxial layers by metalorganic vapor phase epitaxy. The “composition pulling effect” during the initial InGaN growth stages has been studied as a function of the lattice mismatch between the InGaN and the underlying epitaxial layer. The crystalline quality of the InGaN is good near the InGaN/GaN interface and the composition is close to that of GaN. However, with increasing InGaN film thickness, the crystal quality deteriorates and the indium mole fraction increases. The composition pulling effect becomes stronger with increasing lattice mismatch. It is suggested that indium atoms are excluded from the InGaN lattice during the early growth stages to reduce the deformation energy from the lattice mismatch. TEM observations of the InGaN/GaN structure reveal that the degradation of the crystalline quality of InGaN films grown on GaN is caused by pit formation which arises from edge dislocations propagating through the InGaN film from the underlying GaN.

Steroid treatment increases the recurrence of radiation-induced organizing pneumonia after breast-conserving therapy

Radiation-induced organizing pneumonia (RIOP) is an important complication of postoperative radiotherapy for breast cancer. Unfortunately, conventional corticosteroid therapy is frequently associated with relapses. The aim of this retrospective study was to evaluate the outcomes of steroid treatment in patients with RIOP. In total, 26 patients diagnosed with RIOP from among 2404 women who received radiotherapy after breast-conserving surgery for breast cancer were included and classified into steroid (n = 7) and nonsteroid (n = 19) groups. Serum, sputum, and bronchoalveolar lavage composition; subjective symptoms (cough, fever, and dyspnea); migratory progression; and RIOP relapse were compared between the groups. Treatment type did not affect the duration of the subjective symptoms, which was 1.6 and 1.7 months for the steroid and nonsteroid groups, respectively. In contrast, RIOP relapse and new pulmonary lesions developed in five patients in the steroid group and only three patients in the nonsteroid group (P = 0.014). By assessing RIOP duration as the time to resolution of symptoms and discontinuation of therapy, the median duration of RIOP was significantly longer in the steroid (17.1 months) than that in the nonsteroid group (2.3 months, P = 0.005), primarily because of frequent relapses. After remission, persistent pulmonary dysfunction did not occur in the nonsteroid group. This single-center retrospective study demonstrates that steroid therapy results in frequent relapses and significantly prolongs RIOP duration. Corticosteroid treatment is considered a critical factor in RIOP recurrence.

A comprehensive search for mutations in the PKD1 and PKD2 in Japanese subjects with autosomal dominant polycystic kidney disease

To elucidate the genotypic and phenotypic characteristics of autosomal dominant polycystic kidney disease (ADPKD) in Japanese populations, we performed a comprehensive search for mutations in PKD1 and PKD2 in 180 Japanese ADPKD patients from 161 unrelated families. We identified 112 (89 PKD1 and 23 PKD2) mutations within 135 families. Patients with PKD2 mutations account for 23.6% of all Japanese ADPKD families in this study. Seventy-five out of the 112 mutations have not been reported previously. The estimated glomerular filtration rate (eGFR) decline was significantly faster in patients with PKD1 mutations than in those with PKD2 mutations (-3.25 and -2.08 ml min(-1)  year(-1) for PKD1 and PKD2, respectively, p < 0.01). These results indicate that mutations within PKD1 and PKD2 can be linked to most of the cases of Japanese ADPKD, and the renal function decline was faster in patients with PKD1 mutations than in those with PKD2 mutations also in the Japanese ADPKD. We also found that PKD2 mutations were more frequent in Japanese ADPKD than that in European or American ADPKD.

Phase I/II study of gemcitabine plus S-1 with concurrent radiotherapy in patients of unresectable locally advanced pancreatic cancer

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Background: We conducted chemoradiotherapy of gemcitabine plus S-1, key drugs for pancreatic cancer. Methods: Patients were eligible for the study if they had received a histopathological diagnosis of locally advanced pancreatic cancer and were diagnosed as unresectable by multiple clinicians including surgeons due to main arterial invasions and more. Radiation (RT) was perfomed for twenty-eight days continuously except Saturday, Sunday and National holiday in 1.8Gy once daily (total 50.4Gy). PTV was defined as GTV plus 10-15mm. Prophylactic irradiation to regional lymph nodes was not performed. Administration level of the anti-cancer drugs was referred to the following table. Results: A total of fifteen cases were enrolled to the phase I study from February, 2006 through May, 2007. RT was achieved in 13 of 15 cases (87%). Two cases of DLT occurred in level 2 (two cases of emesis) while three did in level 3 (one case of emesis and two of neutropenia of grade 4). We decided level 3 as MTD and level 2 as recommended dose. The overall response rate (more than PR) was 33.3% (5 in 15 cases) and tumor-control (more than SD) was achieved in 13 of 15 cases (87%). The one-year and two-year survival rate was 86.7% and 44.4%, respectively. Conclusions: We conducted the phase 1 study of chemoradiotherapy with two key drugs of pancreatic cancer and achieved the recommended dose in this phase I study. Ongoing study We have already finished the enrollment of 110 cases for a phase II randomized allocated study, comparing the chemoradiotherapy of administration dose decided in this phase 1 study with the combination therapy of gemcitabine plus S-1. Now we are carefully following the patients to compare two-year survival rate as a primary endpoint in phase II study. Clinical trial information: NCT01430052.

An automated rapid detection system using the quenching probe method for detecting interleukin 28B and inosine triphosphatase single nucleotide polymorphisms in chronic hepatitis C

Single nucleotide polymorphisms (SNPs) in the interleukin 28B gene (IL28B) are good pretreatment predictors of anti-hepatitis C virus (HCV) therapy with interferon. SNPs of the inosine triphosphatase (ITPA) gene are associated with reduced haemoglobin levels during treatment with ribavirin. The i-densy™ (Arkray, Inc.), which is based on the quenching probe (QP) method, automatically detects target genes in blood samples by fluorescence quenching within 100 min. Using a QP and primer set, a gene amplification response is generated that can quickly and easily detect a specific gene's arrangement by fluorometry. The present study was conducted to compare the utility of i-densy (QP method) with that of conventional direct sequencing (DS) for detecting SNPs in the IL28B and ITPA genes in chronic hepatitis C patients. Between June 2011 and January 2012, 73 consecutive patients underwent genotyping of IL28B, and 54 patients underwent genotyping of ITPA. All of the patients were seropositive for HCV-RNA. The IL28B and ITPA genotypes were tested for bi-allelic polymorphisms in rs8099917 (T/T, T/G and G/G; minor allele, G) and rs1127354 (C/C, C/A and A/A; minor allele, A), respectively. The results obtained with the QP method were identical to those obtained with the conventional DS method. The frequency of the IL28B genotypes TT, GT and GG were 74%, 24.7% and 1.4%, respectively, and those of the ITPA genotypes CC, AC and AA were 68.5%, 29.6% and 1.9%, respectively. These results indicate that the i-densy using the QP method can automatically, quickly and easily identify genotypes of IL28B and ITPA.

Immunohistochemical localization of aggresomal proteins in glial cytoplasmic inclusions in multiple system atrophy

AIMS

Multiple system atrophy (MSA) is pathologically characterized by the formation of α-synuclein-containing glial cytoplasmic inclusions (GCIs) in oligodendrocytes. However, the mechanisms of GCI formation are not fully understood. Cellular machinery for the formation of aggresomes has been linked to the biogenesis of the Lewy body, a characteristic α-synuclein-containing inclusion of Parkinson's disease and dementia with Lewy bodies. Here, we examined whether GCIs contain the components of aggresomes by immunohistochemistry.

METHODS

Sections from five patients with MSA were stained immunohistochemically with antibodies against aggresome-related proteins and analysed in comparison with sections from five patients with no neurological disease. We evaluated the presence or absence of aggresome-related proteins in GCIs by double immunofluorescence and immunoelectron microscopy.

RESULTS

GCIs were clearly immunolabelled with antibodies against aggresome-related proteins, such as γ-tubulin, histone deacetylase 6 (HDAC6) and 20S proteasome subunits. Neuronal cytoplasmic inclusions (NCIs) were also immunopositive for these aggresome-related proteins. Double immunofluorescence staining and quantitative analysis demonstrated that the majority of GCIs contained these proteins, as well as other aggresome-related proteins, such as Hsp70, Hsp90 and 62-kDa protein/sequestosome 1 (p62/SQSTM1). Immunoelectron microscopy demonstrated immunoreactivities for γ-tubulin and HDAC6 along the fibrils comprising GCIs.

CONCLUSIONS

Our results indicate that GCIs, and probably NCIs, share at least some characteristics with aggresomes in terms of their protein components. Therefore, GCIs and NCIs may be another manifestation of aggresome-related inclusion bodies observed in neurodegenerative diseases.

Preoperative chemoradiotherapy for pancreatic cancer encountered vertebral compression fractures

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Background: Preoperative chemoradiotherapy (CRT) with gemcitabine (GEM) for pancreatic cancer at our institute achieved excellent cure rates, while treated patients encountered vertebral compression fractures (VCFs) frequently. Methods: From January 2006 to December 2011, 220 patients (male/female: 134/86, median age: 66 (range: 33-84)) with resectable pancreatic cancer have been treated with preoperative CRT with GEM. This method consisted of concurrent radiotherapy (50-60 Gy in 25 fractions over 5 weeks) and chemotherapy (GEM 1,000 mg/m2intravenous, weekly for 12-15 weeks, 3 times during 4 weeks). Three-dimensional conformal radiotherapy was used and its fields covered both primary pancreatic tumor and retropancreatic tissues with 50 Gy level. Boost irradiation to the roots of celiac and superior mesenteric arteries with 2.4 Gy/fr using field-within-field technique has been started since 2009. The risk factors for VCF and its causes were retrospectively analyzed for 1,308 Th10-L3 vertebral bodies. Results: Follow-up time from the initiation of CRT ranged from 3.4-73.9 months (median: 17.9). Median overall survival time of these patients was 40.6 months. Radical surgery was completed in 164 patients (75%). Twenty-five patients (11%) diagnosed as VCF (CTCAE v4.0 grade1/2: 12/13) and 22 of them were at 3.6-23 months from CRT. Cumulative incidence rates at 2 years were 18.9% in total, 8.5% in male and 38.4% in female (p = 0.0002). Corresponding rates were 5.1% in age < 60 and 24.9% in age ≥ 60 (p = 0.0107). On their courses 37 de novo VCFs (Th10/11/12/L1/2/3: 2/3/11/13/7/1) were observed at first and 9 patients repeated VCFs near the initial VCFs. Dose-volume factors of each vertebral bodies also significantly correlated with VCF; vertebrae whose mean dose were < 38 Gy/ ≥ 38 Gy developed VCFs in 2.7%/10.0% at 2 years (p < 0.0001), vertebrae whose V30 were < 80%/≥80% developed VCFs in 2.4%/10.6% (p < 0.0001). Conclusions: Besides women and higher age, dose-volume factors of radiotherapy were risk of developing VCF in patients with pancreatic cancer after preoperative CRT with GEM. These findings should be considered to avoid VCFs as late adverse event after CRT for pancreatic cancer, especially in IMRT era.

First demonstration of MC-EDFA-repeatered SDM transmission of 40 x 128-Gbit/s PDM-QPSK signals per core over 6,160-km 7-core MCF

We demonstrate the first 7-core multicore erbium-doped fiber amplified (MC-EDFA) transmission of 40 x 128-Gbit/s PDM-QPSK signals over 6,160-km 7-core multicore fiber (MCF). The crosstalk (XT) from all of the other 6 cores of a MC-EDFA and a 55-km length MCF are about -46.5 dB and -45.6 dB at center core, respectively. The core-to-core rotation approach at every amplified span is used to average the XT of all cores. The averaged optical signal-to-noise ratio (OSNR) after 6,160-km transmission is 15.6 dB with 0.1 nm resolution bandwidth. The Q-factor of all 40 channels surpasses the threshold of the forward-error-correction of 6.4 dB with 1 dB margin after 6,160 km. The total net capacity is 28.8 Tbit/s per fiber and achieved capacity-distance product is 177 Pbit/s.km per fiber. We confirmed the feasibility of MC-EDFA repeatered systems for trans-oceanic transmission.

An aeration control strategy for oxidation ditch processes based on online oxygen requirement estimation

A feedforward-feedback aeration control strategy based on online oxygen requirements (OR) estimation is proposed for oxidation ditch (OD) processes, and it is further developed for intermittent aeration OD processes, which are the most popular type in Japan. For calculating OR, concentrations of influent biochemical oxygen demand (BOD) and total Kjeldahl nitrogen (TKN) are estimated online by the measurement of suspended solids (SS) and sometimes TKN is estimated by NH4-N. Mixed liquor suspended solids (MLSS) and temperature are used to estimate the required oxygen for endogenous respiration. A straightforward parameter named aeration coefficient, Ka, is introduced as the only parameter that can be tuned automatically by feedback control or manually by the operators. Simulation with an activated sludge model was performed in comparison to fixed-interval aeration and satisfying result of OR control strategy was obtained. The OR control strategy has been implemented at seven full-scale OD plants and improvements in nitrogen removal are obtained in all these plants. Among them, the results obtained in Yumoto wastewater treatment plant were presented, in which continuous aeration was applied previously. After implementing intermittent OR control, the total nitrogen concentration was reduced from more than 5 mg/L to under 2 mg/L, and the electricity consumption was reduced by 61.2% for aeration or 21.5% for the whole plant.