Performance of the SolWat system operating in static mode vs. dynamic for wastewater treatment: Power generation and obtaining reclaimed water

Two hybrid SolWat systems operating in static (without flow circulation) versus dynamic (with flow circulation) mode were simultaneously compared. This work aims to demonstrate the viability of SolWat in dynamic mode to: a) adapt to the operation of the WWTP with a continuous flow, in which the wastewater flows continuously for treatment, b) treat a larger volume of water in the system and c) increase the cooling of the PV modules thanks to the cooling of the temperature of the water sample to improve the energy efficiency in the system. Real secondary wastewater effluents from wastewater treatment plants were used, using solar energy for water disinfection and photovoltaic energy production, in order to use the SolWat systems and implement it as a tertiary treatment. A total of five experiments were performed during autumn, winter, spring and summer. Solar disinfection of Escherichia coli, Enterococcus faecalis and Clostridium perfringens was assessed, and physicochemical parameters were also analysed. The UV dose received by the SolWat systems was the same, but not for the microorganisms in the water sample. The static SolWat irradiated a particle (microorganism) for 4 h, while the dynamic SolWat irradiated intermittently, so the latter system received a shorter UV exposure time, and therefore a lower UV dose. Results indicated that, although the microorganisms did not obtain the absolute bacterial inactivation during the SODIS treatment in any SolWat system, adequate inactivation levels were achieved to allow the reuse of the water for various uses (Royal Decree 1620/2007, Regulation (EU) 2020/741), although to a lesser extent for SolWat in dynamic mode, which treated twice the volume of water and reached cooler temperatures. C. perfringens proved to be the most resistant bacterium tested. The total photovoltaic energy production in the dynamic mode system was more energy efficient than the static mode, being even more efficient than the single PV reference system during the spring (3.5%) and summer (2.7%) test, due to the compensating effect by the cooling of the water on the photovoltaic module against the losses caused by radiation.

Using a knowledge, attitudes and practices survey to supplement findings of an outbreak investigation: cholera prevention measures during the 1991 epidemic in Peru

BACKGROUND

To assess the effectiveness of the cholera prevention activities of the Peruvian Ministry of Health, we conducted a knowledge, attitudes, and practices (KAP) survey in urban and rural Amazon communities during the cholera epidemic in 1991.

METHODS

We surveyed heads of 67 urban and 61 rural households to determine diarrhoea rates, sources of cholera prevention information, and knowledge, attitudes, and practices regarding ten cholera prevention measures.

RESULTS

Twenty-five per cent of 482 urban and 11% of 454 rural household members had diarrhoea during the first 3-4 months of the epidemic. Exposure to mass media education was greater in urban areas, and education through interpersonal communication was more prevalent in rural villages. Ninety-three per cent of rural and 67% of urban respondents believed they could prevent cholera. The mean numbers of correct responses to ten knowledge questions were 7.8 for urban and 8.2 for rural respondents. Practices lagged behind knowledge and attitudes (mean correct response to ten possible: urban 4.9, rural 4.6). Seventy-five per cent of respondents drank untreated water and 91% ate unwashed produce, both of which were identified as cholera risk factors in a concurrently conducted case-control study.

CONCLUSIONS

The cholera prevention campaign successfully educated respondents, but did not cause many to adopt preventive behaviours. Direct interpersonal education by community-based personnel may enhance the likelihood of translating education into changes in health behaviours. Knowledge, attitudes, and practices surveys conducted with case-control studies during an epidemic can be an effective method of refining education/control programmes.

Epidemic cholera in the Amazon: the role of produce in disease risk and prevention

Epidemic cholera struck Peru in January 1991 and spread within a month to the Amazon headwaters. A case-control study was done in the Amazonian city of Iquitos, Peru. Cholera-like illness was associated with eating unwashed fruits and vegetables (odds ratio [OR] = 8.0; 95% confidence limits [CL] = 2.2, 28.9) and drinking untreated water (OR = 2.9; 95% CL = 1.3, 6.4). Consumption of a drink made from toronja, a citrus fruit, was protective against illness (OR = 0.4; 95% CL = 0.2, 0.7). Illness was inversely associated with the quantity of toronja drink consumed (P < .01). Produce has not previously been convincingly documented as a risk factor for cholera; this study underscores the importance of washing produce before eating it. Acidic juices, such as toronja drink (pH 4.1), inhibit vibrio growth and may make contaminated water safer. Wild citrus fruits such as toronja are abundant, cheap, and popular in the Amazon region. Promoting the consumption of toronja drink may be a useful cholera prevention strategy in this region.

Epidemic cholera in the Amazon: the challenge of preventing death

Epidemic cholera struck Peru in January 1991, and spread rapidly. The national cholera case-fatality rate (CFR) was less than 1% in the first six months of the epidemic, but in some rural areas, the CFR exceeded 10%. We investigated cholera mortality in the rural Amazon region, an area with a CFR of 6.3%. We conducted a case-control study, comparing 29 decedents with 61 survivors of recent cholera-like diarrheal illness in 12 villages with a combined CFR of 13.5%. Of 29 decedents, 28 (96%) died in the village or en route to a health facility. Death occurred within 36 hours of illness onset for 83% of the decedents. In 11 (92%) villages, the first or second recognized case was fatal. Death was associated with receiving treatment only at home (odds ratio indeterminate; 95% confidence interval 3.5, indeterminate). Treatment with oral rehydration salts (ORS) was not protective against death for patients who received treatment only at home. Treatment with homemade sugar-salt solution (SSS) was also not protective; fewer than one-third of respondents knew the correct SSS recipe. Most decedents experienced multiple barriers to health care. Cholera victims died rapidly and early in village outbreaks, and few patients had access to health care. Provision of threatened villages with ORS supplies and education in their use before cholera strikes is essential to reducing cholera mortality in this region.

Cholera in Piura, Peru: a modern urban epidemic

In late January 1991, epidemic cholera appeared in Peru. Within 2 months, 7922 cases and 17 deaths occurred in Piura, a Peruvian city of 361,868. A hospital-based culture survey showed that 79%-86% of diarrhea cases were cholera. High vibriocidal antibody titers were detected in 34% of the asymptomatic population. A study of 50 case-patients and 100 matched controls demonstrated that cholera was associated with drinking unboiled water (odds ratio [OR], 3.9; 95% confidence interval [CI], 1.7-8.9), drinking beverages from street vendors (OR, 14.6; CI, 4.2-51.2), and eating food from street vendors (OR, 24.0; CI, 3.0-191). In a second study, patients were more likely than controls to consume beverages with ice (OR, 4.0; CI, 1.1-18.3). Ice was produced from municipal water. Municipal water samples revealed no or insufficient chlorination, and fecal coliform bacteria were detected in samples from 6 of 10 wells tested. With epidemic cholera spreading throughout Latin America, these findings emphasize the importance of safe municipal drinking water.