Permeable ditch underwater water purification apparatus

A permeable ditch underwater water purification apparatus purifies source water using the principle of self-purification of water. This apparatus includes impermeable ditch walls on a tapered bottom. The apparatus also has an open top side. A granular filter layer is filled in the ditch body. Collector (counter-rinsing) pipes are provided at the bottom of the granular filter layer, and a filter protecting layer is provided on the surface of the granular filter layer. This apparatus can maintain the thickness of the granular filter layer all the year round. When blockage of the filter layer occurs, water from another ditch is pumped, and the remaining impurities in the granular filter layer can be forced away by water pumped into the collector (counter-rinsing) pipe. After sterilization by adding an appropriate amount of chlorine into the purified water, the quality of water will meet the standards for drinking water in effect in China, and the purified water may be supplied directly for use by the users.

FIELD OF THE INVENTION 
The present invention relates to a novel underwater water purification 
apparatus, and particularly to a permeable ditch water purification 
apparatus located about 1500 mm under the water level. 
BACKGROUND OF THE INVENTION 
Normally, there is no counter-rinsing pipe or no effective counter-rinsing 
pipe in existing riverbed permeable ditches. They can only be built in 
highly permeable riverbeds of considerable thickness. These permeable 
ditches catch impurities in water by using natural or artificial permeable 
layers as filters to attain the object of purification of river water. 
During the functioning of these permeable ditches, the amount of 
impurities caught by the natural or artificial filters may continuously 
increase due to the changes in water quality, resulting in that these 
permeable ditches commonly produce turbid permeated ditch water (usually 
with turbidity higher than degree 5), and resulting in the blockage of the 
permeable ditches. This, in turn, causes a decrease in the water produced 
per unit time with an increase of the functioning time of the permeable 
ditch, thereby, the requirements of the design can not be attained. 
The riverbed purification filtering apparatus described in Chinese Patent 
CN86104417 is an example of using artificial filters. In the disclosed 
apparatus, a purification filtering layer is positioned in the space 
sandwiched between the inner and outer well walls and confined by the 
tapered bottom of the well and a cover of the well wall, wherein rinsing 
porous branch pipes are provided adjacent to the outer well wall. In this 
device, remaining impurities in the filtering layer can be removed to keep 
the quality of water of the water source always clear, as well as to 
prevent the draw down phenomenon of the well. However, this apparatus 
still belongs to the field of side permeating filtering which can only be 
built in permeable riverbeds of certain permeability. Furthermore, the 
well wall cover is a reinforced concrete plate, which makes construction 
and maintenance of the filtering layer complex. 
SUMMARY OF THE INVENTION 
Therefore, it is an object of the present invention to provide a permeable 
ditch underwater water purification apparatus capable of keeping the ditch 
water clear all the year round, and preventing the permeable ditch from 
being blocked, as well as simplifying the procedure of purification. 
The object of the present invention is realized as follows: a 1000 mm thick 
layer of granular filters having diameter 0.6-1.2 mm is provided in an 
open permeable ditch. During the functioning of this layer, source water 
enters from the top and moves into the porous collector pipes 
(counter-rinsing pipes) in the ditch through the surface of the granular 
filter layer. The water collected by the collector (counter-rinsing) pipes 
can meet the national standard for drinking water after being drawn by a 
pump and then sterilized. According to the present invention, the 
remaining caught substances in the filtering layer can be removed 
periodically by pressing air-pressurized water into the collector 
(counter-rinsing) pipes provided at the bottom of the purification 
filtering layer. Thus, the problem of blockage of the permeable ditch can 
be solved.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION 
FIGS. 1 and 2 illustrate the apparatus in accordance with the invention. 
FIG. 1 is a sectional view taken along line 1--1 in FIG. 2. As shown, two 
separate ditch units 12 and 13 may be connected to a single pump 7. 
Referring to FIGS. 1 and 2, a layer of granular filters 4 having a 
diameter d=0.6-1.2 mm and a total thickness (reference number 2 in FIG. 1) 
of 1000 mm is provided in the open permeable ditch 1 and within the 
unpermeable sealing plates 6 at the two ends of the ditch. A filter 
protecting layer 3 covers the upper opening of the permeable ditch. The 
filter protecting layer 3 is composed of two stainless steel nets of 20 
meshes, and a steel bar net covers the stainless steel nets. The steel bar 
of the steel bar net has a diameter of 10 mm, the mesh size of the steel 
bar net is 100 mm, and the steel bar net is used for protecting the 
stainless steel nets. The periphery of the protecting layer 3 is fixed on 
the permeable ditch 1 with a peripheral frame, which prevents the filters 
from being carried away by the water or impurities. The suction pipe 8 of 
the pump 7 is provided with an aperture 9 for adding chlorine for 
sterilization. There is also a parallelly connected suction pipe of the 
pump which is connected with the porous collector (counter-rinsing) pipe 
5, water supply pipe 10 and return rinsing pipe 11. 
In the operation of the permeable ditch, the source water can only enter 
the collector (counter-rinsing) pipes 5 after passing through the 
purification filtering layer 4 from the upper surface of the ditch and 
being purified by the layer 4. The granular filter layer 4 is protected in 
the permeable ditch 1, by protecting layer 3 and sealing plates 6, such 
that even if it is positioned in the source water, it will not be carried 
away by the water or impurities. Thus, the granular filter layer 4 of such 
permeable ditches can maintain its designed thickness all the year round. 
When the amount of water produced becomes less than the designed amount of 
water due to the increase of remaining impurities caught by the granular 
filter layer 4, the rinsing pump can be started to suck water from another 
permeable ditch, and the remaining impurities in the granular filter layer 
4 can be washed away by water spurted upward from the porous collector 
(counter-rinsing) pipe 5 via the return rinsing pipe 11 and the suction 
pipe 8 to recover the designed performance of the granular filter layer. 
This is the method for removing blockages. In order to rinse effectively, 
the porous collector (counter-rinsing) pipe 5 is provided at a lower 
position of the purification filter layer 4. 
The construction of the porous collector pipe 5 is shown in FIG. 3. Pipe 
wall 14 is surrounded with two layers of stainless steel net 15 having a 
20 mesh size. Four rows of apertures are formed in the upper, lower, left 
and right pipe wall, respectively. The diameter of the upper apertures 16 
is 3 mm and the horizontal distance therebetween is 1000 mm. The diameter 
of the lower apertures 18 is 3 mm and the horizontal distance therebetween 
is 500 mm. The left and right rows of apertures are positioned at an angle 
of 45 degrees with respect to the horizontal line passing through the 
center of the cross section of the pipe 5. These rows have apertures 17 
with a diameter of 3 mm and a horizontal distance between the apertures of 
50 mm. Thereby, the filters 4 will not be sucked into the porous collector 
(counter-rinsing) pipes (5) during the water collecting and counter 
rinsing operation of the permeable ditch, such that the permeable ditch 
water can be always kept in good condition. 
The permeable ditch underwater water purification apparatus according to 
the present invention is applicable to rivers, lakes, and reservoirs of 
type I-V water as specified by GB 3838-88 of China, applicable to the 
construction of new water supply plants as well as to the reform of old 
water supply plants on the above-mentioned water sources, applicable to 
the lakes, and applicable to the construction of water supply plants of 
various sizes of the above-mentioned water sources. The dimension of the 
permeable ditch can be as small as one which will produce several tons of 
water every day, or as large as one which will produce tens of thousands 
of tons of water every day. Water supply plants of much larger sizes can 
be constructed using a plurality of ditches. 
Conventional permeable ditches may be blocked due to lack of counter 
rinsing facilities, and can only keep normal water supply for a short 
period. Thus, they can not fully replace the ground sediment filtering 
water supply plant. The process flow of the existing sediment filtering 
water supply plants is normally: water inlet--pump station--adding 
alum--mixing--reaction--sediment--filtering--sterilizing--clean water 
pool--second pump station--user. While the underwater purification 
apparatus according to the present invention has both functions of water 
intaking and purification filtering, the process flow of the water supply 
plant is: permeable ditch underwater water purification 
apparatus--sterilization--pump station--user. The process flow water 
supply plant can be simplified by using the water purification apparatus 
according to the present invention, such that the number of processes is 
reduced from eleven to four, thereby, the area of the plant, investment of 
capital construction, electrical and machinery instruments, as well as 
personnel and labor can be saved. Thus, the cost can be reduced, while the 
quality of water can be ensured to meet the water quality standard of 
drinking water of China, all the year round. In this manner, great 
technical and economical benefits, as well as great social benefits, can 
be achieved.