Continuous retention of floatables – no external energy, no moving parts –

The Challenge

Over­flow events with­in a sew­er sys­tem can pol­lute receiv­ing waters with float­a­bles and sus­pend­ed solids such as plas­tics, paper and san­i­tary arti­cles. Fixed scum boards are stan­dard equip­ment for sew­er net­work over­flows and are used to retain float­a­bles as rec­om­mend­ed by the Ger­man Asso­ci­a­tion for Water, Waste Water and Waste’s guide­lines ATV A‑111.

Often the float­a­bles are sucked under­neath the scum board to the over­flow. This hap­pens when water lev­els rise after heavy rain, caus­ing strong tur­bu­lence, or at drop­ping water lev­els because of the large amount of col­lect­ed float­a­bles in the over­flow cham­ber. The banks of the receiv­ing water­courseare often pol­lut­ed with clear­ly vis­i­ble dirt and sanitarydebris.

The Solution

Bar and brush screens are very effec­tive solu­tions for retain­ing float­a­bles and sus­pend­ed solids with­in the sew­er and allow­ing the debris to be trans­port­ed to the waste­water treat­ment plant. How­ev­er, stressed bud­getary sit­u­a­tions often delay such invest­ments. Screen­ing machin­ery is high­ly effec­tive but also expen­sive because the size must match the max­i­mum pos­si­ble hydraulic spill load.

The HydroSpin^® Float­a­bles Removal sets the bench­mark with a new work­ing prin­ci­ple. For the dura­tion of the rain event – and even with par­tial back­wa­ter – all float­a­bles are con­tin­u­ous­ly drawn into the con­tin­u­a­tion sew­er and thence to treat­ment­by means of an arti­fi­cial vortex.

The System 

The HydroSpin^® Float­a­bles Removal con­sists of the fol­low­ing cham­ber com­po­nents — inflow, out­flow and over­flow. The sys­tem com­po­nents are a com­bined guide and scum board, an adjustable vor­tex plate and a flow-opti­mized vor­tex area which can be fit­ted with addi­tion­al equip­ment as nec­es­sary. The rota­tion­al ener­gy for the arti­fi­cial vor­tex is sup­plied by the flow of the com­bined sewage with­in the cham­ber. In order to gen­er­ate a vis­i­ble vor­tex, the vor­tex plate must be posi­tioned to cre­ate a “flow-opti­mized vor­tex area”.

Installing the vor­tex plate gen­er­ates a water lev­el dif­fer­ence between the inflow and the vor­tex area so that the float­a­bles are con­tin­u­ous­ly guid­ed along the guide scum­board to the vor­tex area and are drawn down­wards into the con­tin­u­a­tion out­let pipe and on to treat­ment. The guide/scumboard com­bi­na­tion has a dou­ble func­tion: it is a scum­board pre­vent­ing debris pass­ing over the spill weirand also a flow-opti­mised guid­ing plate for the floatables.

The HydroSpin^® Float­a­bles Removal relies pure­ly on hydraulic effects. It works con­tin­u­ous­ly even at par­tial impound. It pre­vents an accu­mu­la­tion of float­a­bles so that even with tur­bu­lent flow, a reduc­tion of pol­lu­tant load­ing into the receiv­ing water­course is achieved. The HydroSpin^® Float­a­bles Removal is vir­tu­al­ly main­te­nance free; the con­tin­u­ous vor­tex pro­vides a self-clean­ing effect. The con­tin­u­al removal of float­ing debris into the con­tin­u­a­tion sew­eras­sists in the pre­ven­tion of sed­i­men­ta­tion and block­ages. It is proven that the sim­ple retro­fit of exist­ing cham­bers with the HydroSpin^® Float­a­bles Removal increas­es qual­i­ty per­for­mance and enables a bet­ter pro­tec­tion of the adja­cent sur­face waters.

Data analy­sis from Japan shows an aver­age of up to 78% of float­a­bles and sus­pend­ed solids can be removed from the over­flow using HydroSpin^® Float­a­bles Removal (Naka­mu­ra et al., 2010).

Effi­cient per­for­mance relies on expert knowl­edge of the hydro­dy­nam­ic inter­re­la­tions between the guide board, the vor­tex plate and the vor­tex area. For this rea­son, the hydro­dy­nam­ic design should be car­ried out by Stein­hardt engi­neers. 1,000 instal­la­tions are already in suc­cess­ful operation.

The Advantages:

• con­tin­u­ous float­able removal
• oper­ates even with par­tial impound
• coun­ter­acts debris accumulation
• no elec­tri­cal pow­er nec­es­sary, water-pow­ered vortex
• opti­mal envi­ron­men­tal pro­tec­tion at min­i­mal cost
• retro­fit possible
• no mov­ing parts
• vir­tu­al­ly main­te­nance free