Looking at monitoring the domestic customer comes down to whether or not
there is value in doing so or whether using an empirical (estimated) value which has
been traditional in the water industry is sufficient for purpose. Traditionally, the
amount of wastewater going into the wastewater collection network has been an
estimate of an estimate, insofar as the amount of water supplied into the potable
water network divided by an estimate of the number of customers (2.7 people per
property on average) multiplied by 90% to take into account the amount of drinking
water that never reaches the sewer (because of drinking water, water use on gardens,
etc.). This has led to a per capita consumption (PCC) figure which, in the UK at least,
has historically been 150 L per person per day.
This PCC figure has historically been used as the fundamental basis of design for
the wastewater system. The supporting mechanical water meters were of little use
however, because the meter readings were only taken every 6 months. With the
advent of smart water meters, the situation has changed, and meter readings can
now can be taken on a regular basis, e.g. hourly, thereby providing an appropriate
balance.
This allows for a better visualisation of when water is consumed and, theoretically at least, could be used to imply impacts on the wastewater system. The amount
of water metering across water companies vary greatly, and ranges from 40%
metering in some places [6] to 100% (dumb) metering in others. This is set to
increase drastically over the next few years, with most UK companies planning a
significant proportion of smart water metering of customers.
Translating this into the volumes of wastewater that are produced is difficult in
itself, and, typically, an industry standard of 90% of the potable water use has been
used as a standard for charging the customer. The accuracy of this does depend upon
the socio-economic category of the customer with more affluent people actually
discharging less to the sewer because of potable water use elsewhere (e.g. watering
gardens or topping up swimming pools) [7]. This shows that the estimations of
customer discharges to the sewage collection network are poor at best.
There are domestic wastewater meters on the market; however their uptake is
relatively low, not due to the cost of the meter itself, but more to do with the cost
of installation which can vastly outweigh the purchase cost itself. In short, it is
perceived that the cost of monitoring outweighs the benefit. This is a typical situation
within the smart water industry where the cost-benefit is not truly known, and hence
it is difficult to build business cases [8]. Technologies that are used for potable water
metering are not appropriate as these technologies require a full pipe. The only
technologies that are available would cost £200–300 installed (at minimum) which is
approximately ten times the cost of a customer potable water meter. Over the life of
a typical water meter which is normally 10 years, this would add £20–30 to a
customer’s bill for seemingly very little benefit apart from control of the network.
This is not the case for an industrial customer. For trade effluent the charging
structure, in the UK, is based upon the Mogden formula, which includes not only the
volume but the strength of the wastewater that is discharged to the sewerage network
[1]. As the cost is based upon the volume of the wastewater, there is an economic
value to measuring the flow as accurately as possible, as any uncertainty in the
118
O. Grievson
there is value in doing so or whether using an empirical (estimated) value which has
been traditional in the water industry is sufficient for purpose. Traditionally, the
amount of wastewater going into the wastewater collection network has been an
estimate of an estimate, insofar as the amount of water supplied into the potable
water network divided by an estimate of the number of customers (2.7 people per
property on average) multiplied by 90% to take into account the amount of drinking
water that never reaches the sewer (because of drinking water, water use on gardens,
etc.). This has led to a per capita consumption (PCC) figure which, in the UK at least,
has historically been 150 L per person per day.
This PCC figure has historically been used as the fundamental basis of design for
the wastewater system. The supporting mechanical water meters were of little use
however, because the meter readings were only taken every 6 months. With the
advent of smart water meters, the situation has changed, and meter readings can
now can be taken on a regular basis, e.g. hourly, thereby providing an appropriate
balance.
This allows for a better visualisation of when water is consumed and, theoretically at least, could be used to imply impacts on the wastewater system. The amount
of water metering across water companies vary greatly, and ranges from 40%
metering in some places [6] to 100% (dumb) metering in others. This is set to
increase drastically over the next few years, with most UK companies planning a
significant proportion of smart water metering of customers.
Translating this into the volumes of wastewater that are produced is difficult in
itself, and, typically, an industry standard of 90% of the potable water use has been
used as a standard for charging the customer. The accuracy of this does depend upon
the socio-economic category of the customer with more affluent people actually
discharging less to the sewer because of potable water use elsewhere (e.g. watering
gardens or topping up swimming pools) [7]. This shows that the estimations of
customer discharges to the sewage collection network are poor at best.
There are domestic wastewater meters on the market; however their uptake is
relatively low, not due to the cost of the meter itself, but more to do with the cost
of installation which can vastly outweigh the purchase cost itself. In short, it is
perceived that the cost of monitoring outweighs the benefit. This is a typical situation
within the smart water industry where the cost-benefit is not truly known, and hence
it is difficult to build business cases [8]. Technologies that are used for potable water
metering are not appropriate as these technologies require a full pipe. The only
technologies that are available would cost £200–300 installed (at minimum) which is
approximately ten times the cost of a customer potable water meter. Over the life of
a typical water meter which is normally 10 years, this would add £20–30 to a
customer’s bill for seemingly very little benefit apart from control of the network.
This is not the case for an industrial customer. For trade effluent the charging
structure, in the UK, is based upon the Mogden formula, which includes not only the
volume but the strength of the wastewater that is discharged to the sewerage network
[1]. As the cost is based upon the volume of the wastewater, there is an economic
value to measuring the flow as accurately as possible, as any uncertainty in the
118
O. Grievson