Biofilter for generation of concentrated sulphuric acid from H2S

Biofilters are used for the conversion of odorous hydrogen sulphide to odourless sulphate in wastewater treatment plants under the right conditions of moisture and pH. One of the consequences of maintaining the suitable pH and moisture content is the production of large volumes of weakly acidic leachate. This paper presents a biofilter with a maximum H2S elimination capacity of 16.3 g m(-3) h(-1) and removal efficiency greater than 95 % which produces small volumes (1 mL of solution L(-1) of reactor day(-1)) of sulphuric acid with a concentration greater than 5.5 M after 150 days of continuous operation. The concentrated sulphuric acid was produced by intermittently trickling a minimum amount of nutrient solution down the upflow biofilter which created a moisture and pH gradient within the biofilter resulting in an environment at the top for the bacterial conversion of H2S, while sulphuric acid was accumulated at the base. Genetic diversity profiling of samples taken from different sections of the biofilter confirms that the upper sections of the biofilter had the best environment for the bacteria to convert H2S to sulphate. The formation of concentrated sulphuric acid presents an opportunity for the recovery of sulphur from the waste stream as a usable product.

Enhancement of waste activated sludge anaerobic digestion by a novel chemical free acid/alkaline pretreatment using electrolysis

Anaerobic digestion of waste activated sludge (WAS) is relatively poor due to hydrolysis limitations. Acid and alkaline pretreatments are effective in enhancing hydrolysis leading to higher methane yields. However, chemical costs often prohibit full-scale application. In this study, 12 V two-chamber electrolysis using an anion exchange membrane alters sludge pH without chemical dosing. pH dropped from 6.9 to 2.5 in the anode chamber and increased to 10.1 in the cathode chamber within 15 h. The volatile suspended solids solubilisation of WAS was 31.1% in the anode chamber and 34.0% in the cathode chamber. As a result, dissolved chemical oxygen demand increased from 164 to 1,787 mg/L and 1,256 mg/L in the anode and cathode chambers, respectively. Remixing of sludge from the two chambers brought the pH back to 6.5, hence no chemical neutralisation was required prior to anaerobic digestion. Methane yield during anaerobic digestion at 20 d retention time was 31% higher than that of untreated sludge. An energy balance assessment indicated that the non-optimised process could approximately recover the energy (electricity) expended in the electrolysis process. With suitable optimisation of treatment time and voltages, significant energy savings would be expected in addition to the benefit of decreased sludge volume.

Methane conversion efficiency as a simple control parameter for an anaerobic digester at high loading rates

The anaerobic digestion process is globally applied to the treatment of highly concentrated wastes such as industrial and rural effluents, and sewage sludge. However, it is known to be relatively unstable. When loaded with high concentrations of organic material, unwanted volatile fatty acids (VFA) are often produced rather than methane (CH4) gas which can lead to digester acidification and failure. This study investigated digester behaviour under high loading rates, testing the usefulness of stoichiometric methane conversion efficiency as a digester control parameter at high loading rates. Our results show that, in general, the CH4 production rate was proportional to the feed rate (loading rate). However, at very high loading rates, the CH4 production rate was not proportional to the increase in the feeding rate. Consequently, VFA accumulated and the H2 partial pressure increased. The proportionality of the loading rate and gas production rate is stoichiometrically expressed as the conversion efficiency. We found that conversion efficiency was a useful indicator as an early warning of digester imbalance. The digester remained stable at conversion efficiencies above 75%. Dropping below 70% signified the onset of digester failure. As loading rate and methane production data are readily available on-line in most anaerobic digestion plants, the conversion efficiency can be monitored on-line and used as an efficient control technique to maintain safe operation of anaerobic digesters at high loading rates.

Effect of pre-aeration and inoculum on the start-up of batch thermophilic anaerobic digestion of municipal solid waste

In this study, a short pre-aeration step was investigated as pre-treatment for thermophilic anaerobic digestion of the organic fraction of municipal solid waste (OFMSW). It was found that pre-aeration of 48 h generated enough biological heat to increase the temperature of bulk OFMSW to 60 degrees C. This was sufficient self-heating of the bulk OFMSW for the start-up of thermophilic anaerobic digestion without the need for an external heat source. Pre-aeration also reduced excess easily degradable organic compounds in OFMSW, which were the common cause of acidification during the start-up of the batch system. Careful consideration however must be taken to avoid over aeration as this consumes substrate, which would otherwise be available to methanogens to produce biogas. To accelerate methane production and volatile solids destruction, the anaerobic digestion in this study was operated as a wet process with the anaerobic liquid recycled through the OFMSW. Appropriate anaerobic liquid inoculum was found to be particularly beneficial. It provided high buffer capacity as well as suitable microbial inoculum. As a result, acidification during start-up was kept to a minimum. With volatile fatty acids (VFAs-acetate in particular) and H2 accumulation typical of hydrolysis and fermentation of the easily degradable substrates during start-up, inoculum with high numbers of hydrogenotrophic methanogens was critical to not only maximise CH4 production but also reduce H2 partial pressure in the system to allow VFAs degradation. In a lab-scale bioreactor, the combined pre-aeration and wet thermophilic anaerobic digestion was able to stabilise the OFMSW within a period of only 12 days. The stabilised inert residual material can be used as a soil amendment product.

Solutions to a combined problem of excessive hydrogen sulfide in biogas and struvite scaling

The Woodman Point Wastewater Treatment Plant (WWTP) in Western Australia has experienced two separate problems causing avoidable maintenance costs: the build-up of massive struvite (MgNH4PO4. 6H2O) scaling downstream of the anaerobic digester and the formation of hydrogen sulfide (H2S) levels in the digester gas to levels that compromised gas engine operation and caused high operating costs on the gas scrubber. As both problems hang together with a chemical imbalance in the anaerobic digester, we decided to investigate whether both problems could be (feasibly and economically) addressed by a common solution (such as dosing of iron solutions to precipitate both sulfide and phosphate), or by using separate approaches. Laboratory results showed that, the hydrogen sulfide emission in digesters could be effectively and economically controlled by the addition of iron dosing. Slightly higher than the theoretical value of 1.5 mol of FeCl3 was required to precipitate 1 mol of dissolved sulfide inside the digester. Due to the high concentration of PO4(3-) in the digested sludge liquor, significantly higher iron is required for struvite precipitation. Iron dosing did not appear an economic solution for struvite control via iron phosphate formation. By taking advantage of the natural tendency of struvite formation in the digester liquid, it is possible to reduce the risk of struvite precipitation in and around the sludge-dewatering centrifuge by increasing the pH to precipitate struvite out before passing through the centrifuge. However, as the Mg2+/PO4(3-) molar ratio in digested sludge was low, by increasing the pH alone (using NaOH) the precipitation of PO4(3-) was limited by the amount of cations (Ca2+ and Mg2+) available in the sludge. Although this would reduce struvite precipitation in the centrifuge, it could not significantly reduce PO4(3-) recycling back to the plant. For long-term operation, maximum PO4(3-) reduction should be the ultimate aim to minimise PO4(3-) accumulation in the plant. Magnesium hydroxide liquid (MHL) was found to be the most cost-effective chemical to achieve this goal. It enhanced struvite precipitation from both, digested sludge and centrate to the point where more than 95% PO4(3-) reduction in the digested sludge was achieved.

Severe aplastic anaemia--complete response to antilymphocyte globulin and cyclosporin

Severe aplastic anaemia is uniformly fatal unless treated with immunosuppressive therapy or bone marrow transplantation. The latter is curative in 65% of patients and is the treatment of choice in children and young adults. Antilymphocyte globulin (ALG) and cyclosporin may be used successfully in the absence of an HLA matched sibling donor. We report the case of a twelve-year-old boy with severe aplastic anaemia who received immunosuppressive treatment with ALG and cyclosporin and is alive and well three years and six months post treatment.

HTLV-I serostatus of mothers of patients with adult T-cell leukemia and HTLV-I-associated myelopathy/tropical spastic paraparesis

OBJECTIVES

It has been shown that > 90% of mothers of HTLV-I-infected children were themselves carriers of HTLV-I. This study was designed to determine the HTLV-I serostatus of mothers of patients with adult T-cell leukemia (ATL) and HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP), and to assess the association of age of exposure and disease outcome.

STUDY DESIGN/METHODS

In a cross-sectional study of the HTLV-I serostatus of mothers of HTLV-I-seropositive patients with ATL and HAM/TSP, 36 living mothers of patients with ATL and 15 mothers of patients with TSP/HAM were traced and enrolled.

RESULTS

Five of the 15 (33%) mothers of patients with HAM/TSP and 35 of the 36 (97.2%) mothers of patients with ATL were HTLV-I-seropositive. All patients were breast-fed and none received blood transfusions.

CONCLUSION

This study confirms that infection with HTLV-I in early childhood can lead to ATL in later life, and that HAM/TSP can also result from early infection but more commonly results from infection acquired in adulthood. There are several reports of posttransfusion HAM/TSP, but ATL has not been reported following blood transfusion except in patients who were immunocompromised. Because the newborn infant is considered to be immunoincompetent, it seems that this is a necessary factor for the development of ATL after infection.

Detection of antibodies to human immunodeficiency virus type 1 in oral fluids: a large-scale evaluation of immunoassay performance

Paired serum and oral-fluid (OF) specimens (n = 4,448) were collected from blood donors and patients attending local sexually transmitted disease clinics in Trinidad and Tobago and the Bahamas and were tested for the presence of human immunodeficiency virus type 1 (HIV-1) antibodies. Sera were tested by Abbott AB HIV-1/HIV-2 (rDNA) enzyme immunoassay (EIA), and positive specimens were confirmed by Cambridge HIV-1 and HIV-2 Western blotting (WB). OF specimens were collected with the OraSure collection device and were tested by Murex GACELISA and by two EIAs from Organon Teknika (the Oral Fluid Vironostika HIV-1 Microelisa System [OTC-L] and the Vironostika HIV-1 Microelisa System [OTC-M]). EIA-reactive OF specimens were confirmed by miniaturized WB (OFWB). GACELISA detected all 474 HIV-1 seropositive specimens (sensitivity, 100%). OTC-L detected 470 positive specimens (sensitivity, 99.2%), while OTC-M detected 468 positive specimens (sensitivity, 98.8%). Specificities ranged from 99.2 to 100% for the three assays. Concordance of OFWB with serum WB was 99.4%, and banding patterns determined by the two methods were similar. The immunoglobulin G (IgG) concentration of OF specimens ranged from 0.21 to 100 microg/ml, with a mean of 17.1 microg/ml. Significant differences in OF IgG concentrations were observed between HIV antibody-positive and HIV antibody-negative persons (31.94 versus 15.28 microg/ml, respectively [P < 0.0001]). These data further confirm the suitability of OF specimens for detection of HIV-1 antibodies. Currently available HIV-1 antibody assays provide sensitivities and specificities with OF specimens comparable to those achieved with serum specimens.

Cardiac involvement with lymphoma/leukemia: a report of three autopsy cases

The clinicopathological findings in two patients with ATL and one patient with promyelocytic Leukemia affecting the heart are described. All three cases tested positive for HTLV-I while one of the ATL cases was also positive for HIV. Cardiac infiltrate in the ATL cases varied from microscopic focii in one case to macroscopic infiltration mimicking myocardial infarction in the other case. There were microabscesses in the myocardium in the case afflicted with promyelocytic Leukemia. All three cases had extensive malignant disease with multiple organ infiltration. There was no ante-mortem manifestation of cardiac involvement in any case. The cardiac dimensions were all within the normal range. The possible pathophysiology of cardiac involvement with Lymphoma/Leukemia is discussed.

Pre-operative autologous blood donations. A five-year experience in Trinidad and Tobago

A pre-operative autologous blood donation programme was started in 1988 and made available to all doctors offering elective surgical procedures. Two hundred and seventy-seven (277) patients presented for autologous donation over a five-year period. Nine point four per cent were rejected because of low haemoglobin ( < 10.5 g/dl). The single biggest user of the programme was the Princess Elizabeth Hospital for handicapped persons. Patients undergoing orthopaedic procedures gave 50% of the donations, and ranged in age from 10 to 73 years. The oldest donor was a 73-year-old man who had an abdominal aortic aneurysm replaced. Gynaecological surgeons in the public and private sectors together provided 43.9% of donors, 3.6% of these underwent elective Caesarean Section, each donating one unit of blood at 36 weeks. Patients undergoing general surgical procedures comprised 10.4% of donors. Autologous donors contributed 1.3% of the total number of donations over this period.

Screening for HTLV-1 in healthy blood donors in Trinidad and Tobago, West Indies

Of 1089 healthy blood donors screened for HTLV-1 using ABBOTTS HTLV-1 EIA: 18 (1.7%) were positive; and 16 (1.5%) were confirmed positive using HTLV-1/11 Cambridge Biothec Western Blot method. HTLV-1 antibodies were found amongst the major ethnic groups, viz. Africans, 11 cases (68.75%) and East Indians 4 cases (25%). The mean age of the donors who tested positive for HTLV-1 was 30.75 years; and the male to female ratio was 4.3:1.

Immunophenotypic and HLA studies in childhood acute lymphoblastic leukemia in Trinidad, West Indies

Between October 1983 and May 1986, 17 cases of childhood acute lymphoblastic leukemia (ALL) were admitted to the General Hospital, Port of Spain, Trinidad. Fifteen of those cases were under 10 years of age, seven of whom presented with joint or bone pains. Boys outnumbered girls by almost 5:1 and the ethnic distribution showed a preponderance of patients of East Indian origin. At last follow-up (May 1989), the survival rate of the 15 under-10-year-old patients was 71%. Immunophenotype studies on nine of the 17 patients revealed six carrying T cell markers and three carrying markers suggestive of a pre-B phenotype. HLA tissue typing on 10 patients showed an enhanced frequency of the HLA-B40 antigen when compared with controls (p less than 0.05). This antigen was present in six of the patients typed and four carried the HLA-A2 and B40 antigens together, two of whom also carried the CW3 antigen and the other two carried untypable C antigens. Three of the four carrying HLA-A2 and B40 have died. Two of the three pre-B cases also carried the HLA-A2 and B40 antigens. HLA studies on three of the four families showed that HLA-A2 and B40 were on the same chromosome, i.e., a haplotype inherited from the mother in each case. None of the cases carried the HLA-B5 antigen although this antigen had a frequency of 37.8% in the control group (p less than 0.05). None of the controls with the HLA-B40 antigen carried the CW3 antigen. Further evidence of a disease association must await typing of the D locus antigens but current evidence would suggest an association between HLA-B40 and childhood ALL in Trinidad.

Fanconi's aplastic anaemia in two sisters in Trinidad and Tobago

This report describes two cases of Fanconi's anaemia in Trinidadian sisters of East Indian origin. The cases have been confirmed by chromosomal analysis which showed increased breaks and ring forms. Anorexia was a persistent finding in both cases. One of the sisters also had a poor growth hormone response.

Kaposi sarcoma in the acquired immune deficiency syndrome (AIDS), presenting as lymphogranuloma venereum (LGV) in a promiscuous trinidadian male

A 27-year-old promiscuous male who denied homosexuality, intravenous drug abuse or having received blood transfusions, had disseminated Kaposi sarcoma. The aggressive nature of the tumor in a young man with the Acquired Immune Deficiency Syndrome (AIDS) presenting as lymphogranuloma venereum (LGV) is highlighted. The relation of the HTLV III virus to a diffuse membranoproliferative glomerulonephritis with sclerosis and associated hyaline degenerative changes in the juxtaglomerular apparatus are discussed.

Racial and other characteristics of human T cell leukemia/lymphoma (HTLV-I) and AIDS (HTLV-III) in Trinidad

Adult T cell leukaemia/lymphoma was first recognised as a clinical entity in southwest Japan. Subsequently the Caribbean has been found to be another area where the disease is endemic, and sporadic cases have been identified in different parts of the world. The human T cell leukaemia/lymphoma virus (HTLV-I) is causally related to adult T cell leukaemia/lymphoma. A subgroup of HTLV, designated HTLV-III, has recently been isolated from many patients with the acquired immunodeficiency syndrome (AIDS) and preAIDS, and there is now evidence that this variant is the primary cause of AIDS. This is the first report from Trinidad to describe 12 cases of adult T cell leukaemia/lymphoma and 14 of AIDS. All were in patients of African descent. No cases were seen in subjects of East Indian descent, who, like those of African descent, comprise as much as 40% of the population. West Indians of African descent may have increased susceptibility to infection with both HTLV-I and HTLV-III.

Leukaemia mortality in Trinidad and Tobago 1957-1976

Leukaemia mortality in Trinidad and Tobago over the period 1957-1976 was reviewed. The mortality rate was stable except for an unexplained drop in the adult leukaemia mortality in 1966/67. Throughout the period, annual deaths due to leukaemia were less than one percent of the total annual deaths from all causes. The age and sex patterns of leukaemia mortality were similar to that of the United States of America but the overall mortality rate of 24 per million was low when compared with that of the USA where the rate in 1971 was 70 per million.