THE ELECTRODEWATERING OF SEWAGE SLUDGES

ABSTRACT

Electrodewatering (EDW), the enhancement of conventional pressure filtration by an electric field, is an emerging technology with the potential to improve dewatering especially for difficult materials. CSIRO has many years of experience in EDW, ranging from bench scale tests to demonstration trials. A recent programme has investigated the applicability of EDW to aerobic wastewater treatment sludges which are particularly difficult to dewater using conventional equipment.

The bench scale filtration experiments produced cakes with solids contents of 35-46 wt% using EDW, compared with 24-30 wt% using pressure filtration alone. This paper : ? describes how the dewatering results were achieved;

?identifies a relationship between moisture removal limits by EDW and the forms of water within the sludge;

?shows the results of preliminary attempts to mathematically model the EDW process     

THE ELECTRODEWATERING OF SEWAGE SLUDGES

Electrodewatering (EDW), the enhancement of conventional pressure filtration by an electric field, is an emerging technology with the potential to improve dewatering especially for difficult materials. CSIRO has many years of experience in EDW, ranging from bench scale tests to demonstration trials. A recent programme has investigated the applicability of EDW to aerobic wastewater treatment sludges which are particularly difficult to dewater using conventional equipment.

The bench scale filtration experiments produced cakes with solids contents of 35-46 wt% using EDW, compared with 24-30 wt% using pressure filtration alone. This paper : • describes how the dewatering results were achieved;

•identifies a relationship between moisture removal limits by EDW and the forms of water within the sludge;

•shows the results of preliminary attempts to mathematically model the EDW process     

Persistent fetal circulation: an evolving clinical and radiographic concept of pulmonary hypertension of the newborn

The roentgenographic presentations of 11 newborn infants with hypoxemia secondary to pulmonary vasospasm and subsequent right-to-left shunting of blood through the foramen ovale and/or ductus arteriosus (persistent fetal circulation) are described (P. F. C. Syndrome). One infant had radiographically normal lungs, while ten had pulmonary parenchymal abnormalities including hyaline membrane disease [4], meconium aspiration syndrome [4], or an ill defined pattern of retained lung fluid [2]. The roentgenographic appearance of the lungs, however, was discordant with the severe hypoxemia observed in most. Heart size was variable but some degree of cardiomegaly was commonly present. Tolazoline, a potent vasodilator, was useful diagnostically and may have resulted in increased survival. An expanded clinical and roentgeonographic concept of the PFC syndrome is suggested.     

The satellite RNA of barley yellow dwarf virus-RPV is supported by beet western yellows virus in dicotyledonous protoplasts and plants

The subgroup II luteovirus barley yellow dwarf virus-RPV (BYDV-RPV) acts as a helper virus for a satellite RNA (satRPV RNA). The subgroup II luteovirus beet western yellows virus (BWYV) and the ST9-associated RNA (ST9a RNA), a BWYV-associated RNA that encodes a polymerase similar to those of subgroup I luteoviruses, were assayed for their ability to support replication of satRPV RNA. SatRPV RNA was replicated in tobacco protoplasts in the presence of BWYV RNA or a mixture of BWYV plus the ST9a RNA, but not in the presence of ST9a RNA alone. ST9a RNA stimulated BWYV RNA accumulation which, in turn, increased the accumulation of satRPV RNA. SatRPV RNA was encapsidated in BWYV capsids primarily as circular monomers, which differs from the linear monomers found in BYDV (RPV + PAV) particles. SatRPV RNA was transmitted to Capsella bursa-pastoris plants by aphids only in the presence of BWYV and ST9a RNA. SatRPV RNA reduced accumulation of both BWYV helper and ST9a nonhelper RNAs in plants but did not affect symptoms. The replication of satRPV RNA only in the presence of subgroup II luteoviral RNAs but not in the presence of RNAs with subgroup I-like polymerase genes, in both monocotyledonous and dicotyledonous hosts, suggests that the specificity determinants of satRPV RNA replication are contained within the polymerase genes of supporting viruses rather than in structural genes or host plants.     

Transfection of the gene for B7-1 but not B7-2 can induce immunity to murine malignant mesothelioma

A 56-year-old female with rheumatoid arthritis was admitted because of bilateral hip pain. In a few months of her hospitalization, a relatively abrupt renal dysfunction was emerged besides complement breakdown, and renal biopsy revealed crescentic glomerulonephritis. Immunofluorescence study showed peripheral granular deposits of IgG, IgM, and C3 in the glomeruli. Cresents were predominantly composed of macrophages and glomerular epithelial cells. Amyloid nephropathy, renal vasuculitis, and association of other collagen vascular diseases were negligible for the causative factor. It was suggested that immune complexes were formed in the glomeruli, in which both humoral and cellular immune responses were to be induced, that brought cescents formation in the lesions. Crescentic glomerulonephritis in patients with rheumatoid arthritis is rare and a possible pathogenetic mechanisms involved in the development of renal dysfunction are discussed with the special reference to immune complex-induced inflammation.     

Giant plexiform schwannoma: a report of two cases with soft tissue and visceral involvement

We report two cases of massive, solitary, plexiform schwannoma. One was a 9-cm subcutaneous lesion on the hip of a 72-year-old man who had become aware of the slow-growing tumor 50 years earlier; the other is the first reported plexiform schwannoma to arise in a visceral organ: it arose in the ascending colon of a 54-year-old man and exhibited a dumbbell configuration with submucosal and subserosal components. Neither patient had neurofibromatosis or schwannomatosis. Both tumors were well-circumscribed and multinodular, and both showed a plexiform architecture. Microscopically, the nodules were composed primarily of Antoni A tissue, replete with nuclear palisading and Verocay bodies. Examination by immunohistochemistry and electron microscopy demonstrated the features of well-differentiated Schwann cells; nodules were surrounded by attenuated, residual perineurium. Both patients followed a benign clinical course, without recurrence or metastasis. Neither the large tumor size nor the unusual locations affected the biologic behavior of these neoplasms. A massive plexiform schwannoma must be distinguished from a malignant peripheral nerve sheath tumor and from a plexiform neurofibroma, a tumor prone to malignant transformation.     

Do disease specific characteristics add to the explanation of mobility limitations in patients with different chronic diseases? A study in The Netherlands

STUDY OBJECTIVES: To determine whether disease specific characteristics, reflecting clinical disease severity, add to the explanation of mobility limitations in patients with specific chronic diseases. DESIGN AND SETTING: Cross sectional study of survey data from community dwelling elderly people, aged 55-85 years, in the Netherlands. PARTICIPANTS AND METHODS: The additional explanation of mobility limitations by disease specific characteristics was examined by logistic regression analyses on data from 2830 community dwelling elderly people. MAIN RESULTS: In the total sample, chronic non-specific lung disease, cardiac disease, peripheral atherosclerosis, diabetes mellitus, stroke, arthritis and cancer (the index diseases), were all independently associated with mobility limitations. Adjusted for age, sex, comorbidity, and medical treatment disease specific characteristics that explain the association between disease and mobility mostly reflect decreased endurance capacity (shortness of breath and disturbed night rest in chronic non-specific lung disease, angina pectoris and congestive heart failure in cardiac disease), or are directly related to mobility function (stiffness and lower body complaints in arthritis). For atherosclerosis and diabetes mellitus, disease specific characteristics did not add to the explanation of mobility limitations. CONCLUSIONS: The results provide evidence that, to obtain more detailed information about the differential impact of chronic diseases on mobility, disease specific characteristics are important to take into account.