Development of Chemical Precipitation Purchased Equipment Costs – Sand Filters

This pdf file documents includes items provided by the sand filter vendor used by EPA to develop

purchased equipment costs for sand filters. The vendor provided details and specifications for

continuous backwash gravity sand filters that EPA used in the Steam Electric cost model.

Water Technologies

AstrasandTM Continuous 

Backwash Filter
The ASTRASANDTM filtration system is a new and improved

continuous sand filter, developed for physical-chemical

and/or biological treatment of different types of water,

such as process, waste, surface, cooling and ground water.

The filtration process of the ASTRASAND filter is

comparable to fixed bed filters in that it removes

particulate material. However, its technology offers some

distinct advantages. The ASTRASAND filter operates under

a constant backwash mode, continuously cleaning the

filter bed. This self-cleaning, continuous process allows for

consistently high filtrate quality. Unlike conventional

filtration with starting and stopping of backwash cycles

which are susceptible to increases in flow and loading

rates, the continuous wash water flow of the ASTRASAND

filter is independent of the suspended solids load and the

hydraulic load.

The head loss over the filter is kept at a predetermined

level by either manually or automatically adjusting the

sand recirculation rate. The ASTRASAND filter can be fed by

gravity or by pumps.

Chemical addition, such as with methanol feed for

denitrification, flocculants for P-removal, or oxidizers for

manganese removal, can easily be incorporated into the

ASTRASAND filter without any renovation to the basic

filtration system. 

The design of the ASTRASAND filter is modular and

compact, enabling simple construction, quick installation,

and low maintenance. All of the critical components are

located internally in the filter body, creating a very small

footprint. This makes the ASTRASAND filter an ideal

solution for installations with extreme site restrictions, or

as an add-on to existing treatment systems. The hydraulic

design capacity of the ASTRASAND filter varies between

three and seven gallons per minute per square foot

(gpm/ft2

), depending on the actual application. 

The centering of the airlift assembly is very critical to the

uniformity of the sand circulation rate. Special assembly

procedures have been developed to ensure the correct

position of the airlift pipe.

There are many economical benefits related to the

ASTRASAND filter. In contrast to conventional filtration, no

pretreatment such as flocculation zones are necessary in

situations with high suspended solids loadings. In

addition, because there are no moving parts, wear and

tear is minimal, and operational and maintenance costs

are extremely low. Due to low air consumption demand

and lack of internal pumping, energy costs are low.

Technology & 

Characteristics

2

Municipal wastewater polishing

application for ammonia, BOD,

and suspended solids removal.
3

In municipal applications, the ASTRASAND filter is ideal for

wastewater treatment plants needing to meet stringent

discharge criteria for biochemcial oxygen demand (BOD),

nitrogen (TKN), phosphate (P), and suspended solids

(TSS). The addition of the ASTRASAND filtration process

can leave the existing infrastructure unchanged, without

adding excessive capital costs.

Industrial and process water applications benefit just as

well from the ASTRASAND filtration process. It has proven

its effectiveness in the treatment of surface waters,

ground waters, and side stream (bio)filtration for cooling

water systems. The ASTRASAND filter is also effective in

removing iron and manganese. Washwater or other

process streams can be filtered by the ASTRASAND filter as

part of an overall integrated reuse design. The ASTRASAND

filter is also ideally suited for precipitation and filtration of

metals.

Applications

Industrial wastewater application

where the ASTRASAND is

removing aromatic carbons out of

groundwater.

Surface Water TSS, turbidity, color, PO4-P

Ground Water Fo, Mn, NH4+

Cooling Water biofouling, TSS, turbidity

Washwater Fe, TSS, turbidity

Wasterwater P, TSS, NOx, heavy metals

Biofiltration NH4+, NOx, heavy metals, 

aromatic carbons

Applications Elements Removed
4

Water

The polluted water is transported into the filter by means

of the feed pipeline (1). Water enters the filter bed (4)

through the supply pipe (2) and the distributors (3). This

water is filtered as it flows through the filter in an upward

direction. The filtrate is discharged from the upper part of

the filter (5).

Sand

The filter bed moves downward as the water flows up.

Dirty sand (6) is continuously extracted from the sand bed

and washed by a sand washer (9), after which it is released

back on top of the filter bed (4).

Air

The sand circulation is based on the airlift principle, forcing

a mixture of dirty sand and water upward through a

central pipeline (7). Intensive scouring movements

separate the impurities from the sand particles. At the top

of the pipeline the air is released, and the dirty water is

discharged (8). The sand then settles in the washer.

Sand Washer

The sand washer (9) at the top of the filtration tank

washes the sand with a small amount of clean filtrate. This

removes the final traces of pollutant from the sand. Flow is

achieved through a difference in level between the filtrate

(10) and the wash water (8).

Operation
5

Materials of Construction

According to the customer’s preference, the ASTRASAND filter

can be constructed of carbon steel, stainless steel, fiberglass,

or installed in concrete basins. In very large capacity

installations, concrete may prove to be the more economical

choice. The center airlift and washbox are vital components of

the ASTRASAND filter. They are constructed of high density

polyethelyne (HDPE), which is more durable than other

materials, such as PVC and stainless steel piping.

Process Monitoring and Regulation

The ASTRASAND filtration system has several options available

that separate it from the competition. 

The ASTRAMETERTM is a monitoring system that measures the

sand circulation rate in multiple locations of the filter bed

surface. This allows the operator to measure the uniformity of

the sand circulation, thus monitoring the overall filter’s

efficiency.

The ASTRACONTROLTM is an advanced regulation system that

actually controls the sand circulation rate by measuring the

head loss, feed flow, and temperature. The ASTRACONTROL is

recommended when influent conditions are highly

fluctuating, when strict effluent levels are needed, and when

applying biological processes.

Options

This schematic illustrates a typical process flow for P-removal applications utilizing the

addition of flocculants, as well as biofiltration with the addition of a carbon source.

Left bottom: view of components in a

concrete installation. 

Letf top: view of covers and

ASTRAMETER probe for a concrete

installation.

Right bottom: Municipal wastewater

application for phosphate removal

utilizing chemical addition.

Right top: Stainless steel construction

ASTRASAND filters for ground water

treatment at a sugar factory
ASTRASAND, ASTRACONTROL, and ASTRAMETER are registered

trademarks of Siemens, its subsidiaries or affiliates.

The information provided in this brochure contains merely

general descriptions or characteristics of performance which in

actual case of use do not always apply as described or which may

change as a result of further development of the products. An

obligation to provide the respective characteristics shall only exist

if expressly agreed in the terms of contract.

©2007 Siemens Water Technologies 

All rights reserved.

DV-ASTRASANDdr-BR-0907

Subject to change without prior notice.

www.siemens.com/water
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