Process of ammonia removal from anaerobic digestion and associated ammonium sulphate production: Pilot plant demonstration

A process for the continuous extraction of ammonia from anaerobic digesters is proposed. In this process, a portion of the sludge treated in the digesters is continuously withdrawn and transferred to a thin film evaporator (TFE) unit, where the ammonia is stripped through a biogas stream. The ammonia-rich biogas is treated with a sulfuric acid/water solution in a reactive absorption unit, with production of ammonium sulphate. The chemistry of a CH₄/CO₂/NH₃ gas phase in thermodynamic equilibrium with a liquid sulfuric acid/water solution is investigated theoretically, with focus on the simultaneous absorption of CO₂ and NH₃ into the liquid phase. Pilot plant experimental data confirm the theoretical results. Further pilot plant experimental results obtained during on-off cycles of the stripping equipment demonstrate that, when the TFE unit is off, ammonia concentration in the digestate rises quickly, while, when the stripping equipment is turned on again, ammonia concentration drops down. On average, during the 180 days of pilot plant experimentation, 4.1 g N-NH₄ per kg of sludge fed to the digester, i.e. 19.3 g N-NH₄ per kg of total solids (TS) fed to the digester, are stripped from digestate and recovered as ammonium sulphate, demonstrating the feasibility of the proposed concept.

[Respiratory allergy to nickel. Description of an atypical clinical case]

BACKGROUND

Exposure to nickel sulphate, other than contact dermatitis, can potentially cause respiratory symptoms. Although few cases of occupational rhinitis and asthma are reported in literature, a prolonged exposure can determine sensitization and evolution to respiratory symptoms.

OBJECTIVES

Clinical evaluation of a case of occupational rhinitis and asthma due to nickel sulphate.

METHODS

A female worker, aged 43 years, has been occupationally exposed to nickel for 22 years. After 1 year she experienced asthma, apparently not work related. She treated the respiratory symptoms for many years, but a slow and progressive increase of the disease was observed. During the last five years a straight relationship between work and symptoms was observed. On-off test was positive. The diagnosis of occupational respiratory disease was based on the work-related symptoms and the specific nasal challenge test result.

RESULTS

An early response was observed with nasal symptoms (score 4), increase of anterior nasal airflow resistance (33%), severe dyspnea, haematic eosinophilia, and fall in FEV-1 of 18%.

CONCLUSIONS

The prolonged exposure to nickel determined impairment of respiratory function. Nasal challenge, more safe and useful than bronchial challenge, can be considered gold standard for the diagnosis of occupational rhinitis and asthma due to occupational allergens.

The possible role of cockroaches in baker's asthma

BACKGROUND

Baker's asthma is related to wheat flour exposure and to other cereal dust exposure.

OBJECTIVES

The cockroach is considered a significant allergen and can occasionally trigger asthma in bakery workers.

METHODS

The case of a 33-year-old male, suffering from asthma in the workplace with previous equivocal tests for cereal dust was investigated Clinical assessment of the worker consisted of cutaneous and blood screening for common and occupational allergens, including cockroach. The subject was monitored for aspecific bronchial reactivity and peak flow in a cockroach disinfected workplace, and these data were compared to data obtained after previous workplace exposure.

RESULTS

The worker was not allergic to wheat and other cereal dusts or alpha-amylase, but was sensitized to cockroach. His asthmatic symptoms disappeared, and bronchial reactivity varied after a long period outside the bakery workplace. PEF monitoring, that had showed diurnal variability > 20% and differences between working and non-working periods, demonstrated both normal values and daily variations less than 10% when he returned to the cockroach disinfected workplace.

CONCLUSIONS

The cockroach is a common allergen, however no case of work-related baker's asthma due to the cockroach has been previously described. Clinical history and analysis of the allergens at the workplace must direct the clinical approach of the investigators, in order to correctly evaluate the subject and enable him/her to resume work.

[Urinary MTBE as biological marker of exposure to traffic exhaust fumes]

Methyl tert-butyl ether (MTBE) is an oxygenated compound added to Italian fuel in quantity of about 3% v/v. In the present study the excretion of urinary MTBE (U-MTBE) was evaluated as biomarker of exposure to traffic exhaust fumes. With this aim 127 Milan urban policemen, working as traffic wardens, were investigated. Spot urine samples were obtained prior to and at the end of the work shift, in different seasons. Median U-MTBE varied from 74 to 164 ng/L (range 60-657 ng/L). Comparing the pre-shift and end-shift samples an increase of about 14% in the U-MTBE level during the workshift was observed. An influence of the different seasons was observed, with lower values in spring and higher values in winter. Smoking did not affect the excretion of U-MTBE. The results of this study suggest that U-MTBE is a sensitive and specific marker for the assessment of exposure to traffic exhaust fumes.

[Occupational asthma due to cyanoacrylate: a case-report]

BACKGROUND

An increased use of acrylic compounds is observed in different industries, home repairs and hobbies. These compounds are known to cause skin sensitisation, irritation of mucous membranes and bronchial asthma. Methyl cyanoacrylate is moderately likely to be a sensitizer, while ethyl cyanoacrylate might be a weak sensitizer.

OBJECTIVES

Clinical evaluation of a case of occupational asthma due to cyanoacrylate.

METHODS

A female worker, aged 32 years, used ethyl cyanoacrylate daily. After 2 months she experienced dry cough and shortness breath. Some weeks later she developed bronchial asthma. The diagnosis of occupational asthma was based on the work-related symptoms and the inhalation challenge test result.

RESULTS

A late asthmatic response was observed with a maximum fall in FEV1 of 26% 345 minutes after exposure. Complete clinical and functional recovery was observed after inhalation of a broncho-dilating agent.

CONCLUSIONS

Acrylates are new occupational sensitising agents, causing rhinitis and asthma. It is not possible to perform prick tests or specific IgE measurements for these compounds. The bronchial challenge test is therefore the sole valid test for the diagnosis of occupational asthma.

Transmission of mycobacterium tuberculosis via lung transplantation

Organ donors are not routinely screened for tuberculosis (TB) in the United States. We investigated a case of pulmonary TB in a double-lung transplant recipient. We reviewed the donor's and recipient's records, and used molecular methods to compare the lung recipient's isolate with others from three sources: her hospital, the California state health department's genotyping database, and the donor's resident-nation of Guatemala. A respiratory specimen obtained from the lung recipient 1 day after transplantation grew Mycobacterium tuberculosis. Donor chest radiograph had a previously unnoticed pulmonary opacity that was present on post-transplant recipient chest radiographs and computed tomographs. The recipient's isolate was molecularly distinct from others at her hospital and in the state database, but was identical to two isolates from Guatemala. Tuberculosis was transmitted from lung donor to recipient. As organ transplantation becomes more common worldwide, similar cases could occur. Screening for TB in potential organ donors should be considered.