No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

A longitudinal study of Ascaris lumbricoides reinfection over a 9-10 month period was carried out in a wastewater irrigated fanning region in Central Mexico (September 1989 - May 1991). The study assessed the relationship between different levels of exposure and its components, in the context of wastewater irrigation, and the prevalence and intensity of Ascaris infection. Three farming populations were studied: (1) those who irrigated with untreated or raw wastewater; (2) those who irrigated with wastewater that had sedimented during passage through a storage reservoir (a form of partial treatment); and (3) those who lived in a rain-fed area. Individuals' exposure to Ascaris eggs was estimated by in-depth interviews (characterising the frequency and type of contact with wastewater). Wastewater contact through agricultural activities was also estimated by structured observation. Predisposition to Ascaris infection was largely a consequence of behavioural and environmental factors that caused wastewater contact. Overdispersion of Ascaris intensity in the study population was not age- or gender-dependent. Over the 12-month monitoring period, untreated wastewater had a mean concentration of 96 Ascaris egg/litre and sedimented wastewater a concentration of < 1 Ascaris egg/litre. Contact with untreated wastewater during various activities was associated with differing degrees of excess risk of Ascaris infection in the respective groups: -crop irrigation: 3-fold risk among children -chilli production: 5-fold risk among men and higher intensity infections -tending livestock: 4-fold risk among women -consumption of crops irrigated with wastewater: 2-fold risk in men and children and higher intensity infections in children -sweeping the yard: 5-fold risk in women Contact with sedimented wastewater during play was associated with more than a two-fold risk in Ascaris infection among children, and during maize production, with higher intensity infections among men. The nematode egg guideline of ~l egg/litre is adequate to protect the health of farmers using wastewater in agriculture, but is not sufficient to protect children. Any future modifications of the guideline must consider this.

The dissolved air flotation process experiences process stability problems that are attributed to a poor understanding of the fundamental mechanisms. A detailed review of the literature revealed that the mechanisms of flotation are fairly well understood in mineral flotation application but that the transfer of knowledge to water treatment application is poor, particularly regarding the differences between particle and floc flotation.

Increasing charges by the private utilities for the treatment of industrial waste water are making on-site effluent treatment more attractive. On-site anaerobic digestion is increasingly being used by food processing factories as a cost effective solution to waste liquid waste disposal. Discharge of treated effluent to sewer or water course requires compliance to a maximum admissible concentration (MAC) value, therefore, there is a need for careful control of on-site waste water treatment. This research investigates the treatment of effluent from instant coffee production. This results in a liquid waste that contains recalcitrant and toxic compounds formed during the roasting process. This waste varies in strength and composition according to the different processes that are performed in the manufacture of instant coffee. Anaerobic filters are particularly attractive for wastes containing recalcitrant or inhibitory compounds requiring a long sludge age. Therefore, this study was aimed at firstly investigating the treatability of coffee waste, using anaerobic filters; and secondly monitoring and control of the digestion process in order to maintain a constant effluent quality.

No description available.