Water reuse for irrigation from waste water treatment plants with seasonal varied operation modes

Abstract

Irrigation periods are usually limited to vegetation periods. The quality requirements for treated wastewater for disposal and for reuse are different. The reuse of water for irrigation allows partly the reuse of the wastewater's nutrients (N and P). Outside the irrigation period the water must be treated for disposal, thus nutrient removal is often required in order to avoid detrimental effects on the receiving surface water body. Only wastewater treatment plants with different operation modes for different seasons can realise these requirements. The nitrification is the most sensitive biological process in the aerobic wastewater treatment process. At low water temperatures the nitrifying bacteria need several weeks to re-start full nitrification after periods without NH4-removal. Therefore it is necessary to develop options for waste water treatment plants which allow a fast re-start of the nitrification process. Based on theoretical considerations and computer simulations of the activated sludge treatment process, one possibility for implementing a wastewater treatment plant with different seasonal operation modes is evaluated.

The impact of wastewater irrigation on the chemical quality of groundwater

“…). With regard to the environment, key beneficial factors include: a reduction in freshwater demand; the recharging of aquifers; the recovery of wastewater nutrients, which reduces fertiliser applications; and the soil‐aquifer treatment, leading to a reduction of direct discharge and the eutrophication of water bodies (Papaiacovou ; Cornel & Weber ; Gori et al . ; Campling et al .…”

“…Wastewater reuse has both positive (beneficial) and negative (risky) sides related to environmental, economic and social features (Campling et al 2008). With regard to the environment, key beneficial factors include: a reduction in freshwater demand; the recharging of aquifers; the recovery of wastewater nutrients, which reduces fertiliser applications; and the soil-aquifer treatment, leading to a reduction of direct discharge and the eutrophication of water bodies (Papaiacovou 2001;Cornel & Weber 2004;Gori et al 2004;Campling et al 2008). The negative (risky) factors considered are mainly in relation to human and environmental health aspects, for example infections with water-borne pathogens (Carr et al 2004;Candela et al 2007).…”

Aerated biofilter with seasonally varied operation modes for the production of irrigation water

“…The start-up of an ASP plant might take longer. Cornel & Weber (2004) indicate a time span of > 70 days for starting nitrification at 14''C without inoculation with nitrifying sludge.…”

“…Basically, the implementation of separated process steps for carbon removal and nitrogen removal is favourable, since to modify the treatment level of a single process may be a complex and time-consuming task, as has been shown by Popel (1999) and Cornel & Weber (2004) for the activated siudge process (ASP). The time requirement for re-starting nitrification in the ASP strongly depends on the temperature: full nitrification can be reached after 10 days at 25''C and after 70 days at H^C by only increasing the sludge retention time.…”

“…In case nitrifying sludge is available (e.g. from another plant) and added to the carbon removal process step, a re-start of nitrification could be much faster and would only take 5 days at 25X and 20 days at 14°C (Cornel & Weber 2004).…”