Evaluation of Decentralized, Closely-Spaced Precipitation Water and Treated Wastewater Infiltration

Abstract

Decentralized water management requires innovative technical solutions due to restricted operational and economic resources. In this study, a combined, decentralized infiltration system in the form of closely-spaced sub-systems for precipitation water and treated wastewater has been numerically analyzed. Flow and transport simulation shows that a closely-spaced system, by arranging the infiltration pipes closely in a longitudinal manner, is feasible under the consideration of German national guidelines for both infiltration methods. Precipitation events up to a recurrence interval of five years can be infiltrated alongside with treated wastewater of a one-family house without significant reduction of the wastewaters’ residence time. Scenario analyses highlight that harmless wastewater infiltration remains mainly undisturbed for a broad bandwidth of hydrological, subsurface, and technical conditions.

Numerical and Laboratory Investigations of Closely-Spaced and Joint Infiltration of Precipitation and Treated Waste Water

“…Finally, this reveals that, at least for the conditions studied here, a closely-spaced as well as a joint infiltration of both treated waste water and precipitation water seems principally applicable. This is also in agreement with the numerical study that was conducted by [20], where a broad set of scenarios has been investigated and that provided the base of this study.…”

“…To ensure stable composition of the treated waste water in the meantime, it was stored at a temperature of 4 • C. The infiltration of the synthetic precipitation containing 6.86 mg L −1 NaNO 3 , 1.64 mg L −1 KHCO 3 , and 26.96 mg L −1 CaSO 4 is based on an event of a statistical recurrence interval of five years (rated precipitation according to the German guideline for infiltration [29]). The respective length and intensity is gained while using KOSTRA-DWD [30] data valid for a site in Saxony (Schöneck im Vogtland, same site, as used by [20]). Based on the hydraulic conductivities of the used sediment (see Table 1), an event of statistical recurrence interval of five years has an event period length of 120 min.…”

“…and an intensity of 51.6 L s −1 ha −1 . Together with assumptions for a one-family house [20], the total precipitation volume to be stored and infiltrated in the ditch results to 11,703 L. According to [29], an infiltration ditch with a volume of 6.0 m × 2.0 m × 2.5 m is sufficient for this purpose. As done for the waste water infiltration, downscaling of the precipitation water quantity to be infiltrated in the 3D laboratory tank occurred with a factor of 225 (15 × 15) due to the infiltration of the precipitation water by the rectangular base area of the ditch.…”

“…It can be expected that water content is not evenly distributed in the tank due to previous experiments. The clay barrier for the separated ditches was parameterized after [20]. The ditch gravel has been simulated based on laboratory data and assumptions, among others, made for ditch dimensioning (hydr.…”

Economic Incentives in Stormwater Management: A Study of Practice Gaps in Poland

“…Dimensioning of the bioswale as a retention-infiltration device is carried out on the basis of rules defined by German regulation guidelines DWA-A 138, 2005 [58,59]. The design parameter of retention-infiltration systems is the retention capacity V r , which is determined by the relationship:…”