Viabilidad de huevos de helmintos en biosólidos

El trabajo consistió en determinar el tiempo de almacenamiento (deshidratación natural en zona de clima templado) necesario para que los lodos acumulados en las lagunas de sedimentación, pudiesen ser utilizados en la agricultura sin riesgo sanitario, para lo cual se estudio la viabilidad de los huevos de helmintos a través del tiempo. Dado que la concentración de huevos de helmintos parásitos en los lodos de la localidad de Alcorta, prov. de Santa Fe, fue baja (1-2 huevos/g MS) se decidio adicionar huevos de Ascaris artificialmente, para estudiar su viabilidad

Viabilidad de huevos de helmintos en biosólidos

El trabajo consistió en determinar el tiempo de almacenamiento (deshidratación natural en zona de clima templado) necesario para que los lodos acumulados en las lagunas de sedimentación, pudiesen ser utilizados en la agricultura sin riesgo sanitario, para lo cual se estudio la viabilidad de los huevos de helmintos a través del tiempo. Dado que la concentración de huevos de helmintos parásitos en los lodos de la localidad de Alcorta, prov. de Santa Fe, fue baja (1-2 huevos/g MS) se decidio adicionar huevos de Ascaris artificialmente, para estudiar su viabilidad

Solid-liquid separation of faecal sludge using drying beds in Ghana: implications for nutrient recycling in urban agriculture.

This study investigated the possibility of recycling nutrients in human excreta and municipal solid waste for use in agriculture. It reports on the use of drying beds in separating solid and liquid fractions of faecal sludge (FS) so that the solids can be co-composted and the organic matter and part of the nutrients captured for urban agriculture. Sludge influent onto drying beds, percolate effluent, and dewatered sludge (biosolids) were monitored over eight loading cycles in 2002. The unplanted drying beds were made of 15 cm of sand (0.2-0.6mm diameter) and 25 cm gravel (10 and 19 mm diameter). The loading rate of sludge ranged from 196 to 321 kg total solids (TS) /m(2)y. Biosolids with TS 20% were obtained after an average drying time of 2 weeks. The drying beds retained 80% of solids and 100% of helminth eggs. The biosolids had average organic matter content of 61%; hence, allowing for co-composting with biodegradable organic solid waste for hygienisation. The process is being investigated further to attain higher efficiency and reliability.

Investigating helminth eggs and Salmonella sp. in stabilization ponds treating septage.

Sludge management arises as a relevant problem after being accumulated in primary ponds of septage treatment plants. One of the most attractive options for sludge disposal is its use in agriculture and then specific guidelines regarding hygienic quality must be fulfilled. This study aimed at evaluating the storage time needed to inactivate Ascaris eggs and Salmonella in sludge accumulated in a primary pond treating septage. Raw septage exhibited very low concentrations of viable Ascaris eggs, thus experiments with Ascaris suum eggs spiking were conducted. The concentration of Ascaris eggs in the solids accumulated at the bottom of the pond was 20 eggs/g of total solids (g TS) at the time of pond closure. Although it decreased, some eggs remained viable (0.59 mean viable eggs/g TS) up to 20 months of in-pond storage of the biosolids. Salmonella survival was studied after developing an analytical method that inhibited the native flora. Sludge was seeded with Salmonella enteritidis. An equation adequately describing Salmonella die-off in biosolids subjected to 115 days of in-pond storage/dewatering, was found to be represented by the regression: y = log MPN Salmonella/g TS = 6.67 x t(-0.086), with t = storage time elapsed in days. The initial concentration was 7.0 x 10(6) MPN/g TS and the removal efficiency was 99%.

Isolation of Salmonella sp. in sludge from septage treatment plant.

Waste stabilization ponds (WSP) are an often-used option to treat faecal sludges collected from on-site sanitation systems. Since agricultural use is one of the most attractive options for sludge disposal, specific guidelines on the hygienic sludge quality must be fulfilled, such as for viable helminth eggs and Salmonella sp. Although Salmonella isolation methods are well known for other types of samples, they are not suitable for faecal sludge. The reason can be attributed to the co-existence of a native bacterial sludge flora masking Salmonella development, especially if this bacteria is present at low concentrations. In order to select the best methodology for Salmonella recovery from septage sludge, different culture media were assayed at different incubation periods and temperatures. The proposed methodology for Salmonella recovery from sludge can be summarised as follows: (1) enrichment in Rappaport-Vassiliadis broth at 43 degrees C, 48 hours, and (2) isolation in XLD agar at 40 degrees C, 24 hours. Identification of suspected colonies by biochemical tests: TSI, LIA, urease and serological confirmation with Group O Antigen.

Treatment of septage in constructed wetlands in tropical climate: lessons learnt from seven years of operation.

In tropical regions, where most of the developing countries are located, septic tanks and other onsite sanitation systems are the predominant form of storage and pre-treatment of excreta and wastewater, generating septage and other types of sludges. The septage is disposed of untreated, mainly due to lack of affordable treatment options. This study presents lessons that have been learned from the operation of pilotscale constructed wetlands (CWs) for septage treatment since 1997. The experiments have been conducted by using three CW units planted with narrow-leave cattails (Typha augustifolia) and operating in a vertical-flow mode. Based on the experimental results, it can be suggested that the optimum solids loading rate be 250 kg TS/m2 yr and 6-day percolate impoundment. At these operational conditions, the removal efficiencies of CW units treating septage at the range of 80-96% for COD, TS and TKN were achieved. The biosolid accumulated on the CW units to a depth of 80 cm has never been removed during 7 years of operation, but bed permeability remained unimpaired. The biosolid contains viable helminth eggs below critical limit of sludge quality standards for agricultural use. Subject to local conditions, the suggested operational criteria should be reassessed at the full-scale implementation.

Cotreatment of sewage and septage in waste stabilization ponds.

A one year study was carried out in a waste stabilization ponds system where septage and sewage are cotreated. The system consists of two septage ponds which operate alternately followed by two ponds in series which receive the combined effluent. The septage ponds also act as evaporation ponds for the accumulated sludge. The monitoring program was divided in two phases. The results of the first phase indicate that the effluent of septage ponds has an adequate quality to be discharged into the waste stabilization ponds designed to treat sewage and that is possible to use the septage ponds to dry the accumulated sludge. Further investigation is needed to find suitable post-treatment of the sludge in order to use it in agriculture.

Septage dewatering in vertical-flow constructed wetlands located in the tropics.

Constructed wetlands (CWs) have been proven to be an effective low-cost treatment system, which utilizes the interactions of emergent plants and microorganisms in the removal of pollutants. CWs for wastewater treatment are ndrmally designed and operated in horizontal-flow patterns, namely, free-water surface or subsurface flow, while a vertical-flow operation is normally used to treat sludge or septage having high solid contents. In this study, three pilot-scale CW beds, each with a surface area of 25 m2, having 65 cm sand-gravel substrata, supported by ventilated-drainage system and planting with narrow-leave cattails (Typha augustifolia), were fed with septage collected from Bangkok city, Thailand. To operate in a vertical-flow mode, the septage was uniformly distributed on the surface of the CW units. During the first year of operation, the CWs were operated at the solid loading rates (SLR) and application frequencies of, respectively, 80-500 kg total solid (TS)/m2 x yr and 1-2 times weekly. It was found that the SLR of 250 kg TS/m2 x yr resulted in the highest TS, total chemical oxygen demand (TCOD) and total Kjeldahl nitrogen (TKN) removal of 80, 96 and 92%, respectively. The TS contents of the dewatered septage on the CW beds were increased from 1-2% to 30-60% within an operation cycle. Because of the vertical-flow mode of operation and with the effectiveness of the ventilation pipes, there were high degrees of nitrification occurring in the CW beds. The nitrate (NO3) contents in the CW percolate were 180-250 mg/L, while the raw septage had NO3 contents less than 10 mg/L. Due to rapid flow-through of the percolates, there was little liquid retained in the CW beds, causing the cattail plants to wilt, especially during the dry season. To reduce the wilting effects, the operating strategies in the second year were modified by ponding the percolate in the CW beds for periods of 2 and 6 days prior to discharge. This operating strategy was found beneficial not only for mitigating plant wilting, but also for increasing N removal through enhanced denitrification activities in the CW beds. During these 2 year operations, the dewatered septage was not removed from the CW beds and no adverse effects on the septage dewatering efficiency were observed.

On-site sanitation: when the pits are full--planning for resource protection in faecal sludge management.

In urban centres of industrializing countries, the majority of houses are served by on-site sanitation systems such as septic tanks and unsewered toilets. The faecal sludges (FS) collected from these systems are usually discharged untreated into the urban and peri-urban environment, posing great risks to water resources and to public health. Contrary to wastewater management, the development of strategies to cope with faecal sludges, adapted to the conditions prevailing in developing countries, have long been neglected. The authors describe the current situation in FS management and discuss important issues regarding FS management. Further, treatment options are presented which may prove sustainable in industrializing countries. The objective is to make planners and decision-makers aware of the challenges posed by faecal sludges and of the need to include FS management in strategic planning for urban sanitation improvements.