Model-based comparison of two ways to enhance WWTP capacity under stormwater conditions

Two different approaches to increase the fraction of combined water treated in the wastewater treatment plant (WWTP) which would otherwise contribute to combined sewer overflows (CSO) are presented and compared based on modelling results with regard to their efficiencies during various rain events. The first option is to generally increase the WWTP inflow according to its actual capacity rather than pre-setting a maximum that applies to worst case loading. In the second option the WWTP inflow is also increased, however, the extra inflow of combined water is bypassing the activated sludge tank and directly discharged to the secondary clarifier. Both approaches have their advantages. For the simulated time series with various rain events, the reduction of total COD load from CSOs and WWTP effluent discharged to the receiving water was up to 20% for both approaches. The total ammonia load reduction was between 6% for the bypass and 11% for inflow increase. A combination of both approaches minimises the adverse effects and the overall emission to the receiving water.

Modelling of enhanced CSO treatment in secondary clarifiers with a modified Activated Sludge Model no. 3

An alternative approach for combined water treatment as opposed to its CSO discharge into receiving water is its bypass to the inlet of secondary clarifiers (SC). To analyse the processes and to evaluate the performance of this approach, experiments and numerical modelling were carried out. In batch and pilot scale experiments major effects were identified and quantified. The Activated Sludge Model No. 3 (ASM3) was modified to simulate the batch and pilot scale experiments for implementation of the bypass-specific processes and thus to set up an overall balance of the relevant compounds. With some modifications of ASM3, good agreement of the modelling results with measurements of COD, nitrogen and phosphorus were achieved.

Utilization of activated sludge plants for enhanced treatment of combined sewage

A process is introduced which utilizes secondary clarifiers for the treatment of combined sewage. Under storm water conditions, surplus sewage bypasses the aeration tanks after primary treatment and is directly introduced into the secondary clarifiers. The hydraulic capacity of existing activated sludge plants can be increased without additional tank volume. Particulate matter as well as dissolved compounds are removed to a high extent. Investigations on a full scale treatment plant (100,000 p.e.) show that the effluent quality is comparable with full biological treatment, even if the hydraulic loading is increased by 50%.

"Fast-track" rehabilitation for elective colonic surgery in Germany--prospective observational data from a multi-centre quality assurance programme

BACKGROUND

The results of "Fast-track" colonic surgery in an unselected population outside of specialised units has been unknown yet.

MATERIALS AND METHODS

Data from 24 German hospitals performing "Fast-track" rehabilitation as the standard peri-operative care for patients undergoing elective colonic resection were collected in a prospective multi-centre study conducted between April 2005 and September 2006 to evaluate local and general morbidity.

RESULTS

One thousand and forty-seven patients undergoing elective "fast-track" colonic resection were included. Compliance to essential parts of "fast-track" rehabilitation was high (epidural analgesia 86,6%, early oral feeding and mobilisation on the day of surgery 85.5 and 85.4%). Surgical morbidity was observed in 148 patients (14.1%) and general morbidity in 95 patients (9.1%), while mortality was 0.8%. Predefined discharge criteria were met within 5 (1-83) days after surgery, but because of economical restraints in the German DRG system, patients were discharged only after 8 (3-83) days. Re-admission rate was 3.9%.

CONCLUSION

"Fast-track" rehabilitation for elective colonic resection was safe and feasible in German hospitals of all sizes and yielded a low general morbidity and re-admission rate. Post-operative recovery was enhanced, but discharge from hospital was delayed because of economical reasons.

[Problem-based learning for surgery. Increased motivation with less teaching personnel?]

BACKGROUND

Traditional teacher-centred education strategies often do not meet the needs and student abilities of adult learning. The introduction of small learning groups requires considerable increases in staff. Problem-based learning could increase the motivation to acquire knowledge but without being as staff-intensive.

METHODS

Medical students (n=98) in their fourth clinical semester were randomly assigned to either a structured course (SC) or problem-based learning (PBL) for surgery. Their motivation and acceptance of the courses were recorded at the end of term in anonymous questionnaires using Likert scales, with scores ranging from 1 (very good) to 6 (unsatisfactory).

RESULTS

Both course structure and the teachers received much better ratings from the PBL students (P<0.01 each). The motivation of students to deal with surgical problems beyond the course material was significantly higher after PBL, with 1.8 (0.7), than after the structured course with 3.1 (1.2) (P<0.01). The overall rating was substantially worse for the structured course, with 3.1 (1.2) than for PBL at 1.4 (0.6) (P<0.01).

CONCLUSIONS

Problem-based learning in the surgical curriculum increases student acceptance and motivation with little demand on staff. It should be increasingly implemented.

Wandel der perioperativen Therapie bei elektiven kolorektalen Resektionen in Deutschland 1991 und 2001/2002

BACKGROUND

To assess changes in perioperative treatment of patients undergoing elective colorectal resections, surveys were sent to all German surgical departments in 1991 and 2001/2002.

METHODS

1,207 chairmen of departments for general or visceral surgery were asked to answer a survey concerning the principles of perioperative treatment of patients undergoing elective colorectal resection. The results of this questionnaire were compared to a survey that had been performed in 1991.

RESULTS

616 chairmen (51.0%) responded to the survey (1991: 76.4%). In 2001/2002 preoperative parenteral alimentation was utilized routinely in only 10.3% (1991: 40.0%) of all hospitals. Preoperative i.v.-pyelography was used only in 24.7% of the hospitals (1991: 79.7%). Intraoperative testing of colorectal anastomoses was more common in 2001/2002 (63.7%) than in 1991 (40.1%). At the same time the incidence of "single-shot"-antibiotic prophylaxis increased from 24.0% to 70.4 %. Orthograde bowel lavage, perioperative antibiotic prophylaxis and postoperative parenteral alimentation were use as often in 2001/2002 as in 1991. Intraperitoneal drains were routinely inserted in most of the surgical departments after left-sided colonic resections (2001/2002: 86.2%; 1991: 88.2%) or rectal resections (2001/2002: 90.5%; 1991: 94.4%).

CONCLUSION

During the last decade, perioperative therapy for patients undergoing elective colorectal resection has changed substantially. Most of these changes occurred in the perioperative medical treatment. However, surgical traditions like intraperitoneal drainage are still very frequently utilized.

Protein microheterogeneity and crystal habits: the case of epidermal growth factor receptor isoforms as isolated in a multicompartment electrolyzer with isoelectric membranes

A purified, soluble form of the epidermal growth factor receptor (sEGFR) was found, by isoelectric focusing in immobilized pH gradients, to consist of three major isoforms (with pI values 6.45, 6.71 and 6.96, respectively) and ca. a dozen minor components. This wild-type sEGFR, while producing crystals, has so far defied any attempt at decoding the structure, due to the very poor diffraction pattern. When the wild-type sEGFR was purified in a multicompartment electrolyzer with isoelectric Immobiline membranes, it yielded the three major isoforms as single-pI components, collected in three separate chambers of the recycling electrolyzer. The pI 6.71 and the pI 6.96 isoforms produced large crystals of apparent good quality. However, while the former produced a high-quality diffraction pattern, which may lead to decoding of three-dimensional structure, the pI 6.96 produced crystals which did not diffract at all. It is concluded that, in the case of "tough" proteins (large size, heterogeneous glycosylation, high water content of crystals), purification to single-charge components might be an essential step for growing proper crystals. The unique advantage of purification via isoelectric membranes is that the protein is collected both isoelectric and isoionic, i.e. uncontaminated by soluble buffers (such as the carrier ampholytes used in conventional focusing).

The secreted form of the epidermal growth factor receptor. Characterization and crystallization of the receptor-ligand complex

A protein composed of the external domain of the epidermal growth factor (EGF) receptor is secreted by A431 human tumor cells. The soluble receptor protein was isolated in bulk quantities from cell culture supernatants. It has an intact ligand binding site, exists in a 93-kDa monomeric form, and does not undergo oligomerization upon ligand binding; thus the receptor dimerization reported for the EGF holoreceptor appears not to be a function of its external domain. The unique system of a physiological soluble receptor was utilized for a crystallization study. Crystals were obtained but only in the presence of the ligand. They contained (in equimolar amounts) receptor as well as EGF. The crystals belong to the tetragonal space group P4(3)2(1)2 or P4(1)2(1)2 with unit cell dimensions a = b = 118 A, c = 202 A. The packing density parameter was 3.55 A3/dalton, indicating the asymmetric unit to consist of one receptor-ligand complex.