Under the press of globle water resource shortage, harvested rainwater has been
widely used to provide not only process water but also domestic water consumption in
China and many other coutries. It is an important issue to investigate water quality
variation of harvested rainwater as drinking water source in micro-storage facilities and its
influence on safety of drinking water. Aiming at a number of problems with water quality
issue during rainwater utilization, the paper took some typical water quality parameters
closely related to human health as researcher object, studied characteristics and mechanism
of the spatio-temporal variability of the referred pollutants, by means of indoor and
outdoor experiment and theoretical analysis. The main conclusions are listed as follows:
1. Simulation and analysis of temporal variation of typical pollutants concentration in
harvested rainwater. During storage process, the concentration of pollutants gradually
reduced with time, and reached a stable trend in 20~30 days, which agreed with effect of
self-purification. According to the measured results of temporal variation in pollutants
concentration, the temporal migration process changes of pollutants could be dividend into
three stages, viz. the early settlement-dominant period, the transition period and the
diffusion-dominant period. A numerical model was established for describing the temporal
changes of pollutants in small and micro-rainwater utilization engineering, validated and
evaluated. And turbidity and COD werer verified well by the monitoring results; nitrogen
compounds had a certain deviation, but a rational trend. 20-30 days after storage was
recommended as suitable time for utilization.
2. Simulation and analysis of vertical distribution of typical pollutants concentration
in rainwater. Turbidity and COD contents are high at two ends and low in the middle along
the vertical line, due to sediment at the bottom and floating debris at the surface and
biological activities. Sediment and floating debris are two main pollution sources. Along
the vertical line, the measured relative pollutant content was positively correlated to the
power function of relative distance from the pollution source. Several types of vertical distribution were given based on the measured data. So low pollutant content appears in
the middle, and cleanness of surface and bottom could improve harvested rainwater quality.
A numerical model was established for describing the vertical distribution of pollutants in
small and micro- rainwater utilization engineering, validated and evaluated, and was
verified by the monitoring results, which had certain deviation, but credible usage. A
relative depth of 0.4-0.6 h was was recommended as suitable zone for utilization.
3. The effect of MBER soil stabilizer, compared with cement material, as construction
materials on water quality was studied. With the effect of soil stabilizer, during storage
time, the pollutants concentration decreased about 15~20%; as for the vertical distribution,
the relative concentration decreased about 8~12%. The effect of solidified soil using
MBER soil stabilizer was due to the hydrate reaction of solidified soil and reaction
products. Soil stabilizer could strengthen self-purification of water to some extent, which
could reduce the amount of turbidity, COD and some ions such as nitrate and nitrite.
Results showed that the water quality did not exceed the standard for drinking water in
China for distribute water supply. Results in this research were valuable for popularization
and application of MBER soil stabilizer in rainwater utilization from point view of water
4. A suitable water quality assessment method was given. Turbidity, COD, ions (such
as nitrate) and pH were chosen as the main factors or indicators for describing the
characterization of rainwater quality using statistics analysis method. The rainwater quality
assessment method was presented as a result to security drinking water quality. Through
data analysis and comparison, the method is intuitive, reliable and targeted.
5. The suitability of different spatial scales of rainwater utilization was investigated.
Harvested rainwater utilization in the rural single family courtyard, small watershed was
investigated and evaluated. Results showed that: rainwater utilization had great potential
in solving the rural household in dingbian. Rational utilization of rainwater resources is a
suitable strategy to alleviate the problem of drinking water safety in rural area.
Key words: rainwater storage facilities; drinking water safety; spatio-temporal variation; water quality
index; soil stabilizer