JPH0536393B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to the treatment of aquatic plants used to purify water bodies, and particularly to a treatment method suitable for water hyacinth. In recent years, methods of cultivating aquatic plants and ingesting nutrients from the water have been used to purify water bodies, and water hyacinth is particularly promising, but the collected water hyacinth has a high water content. If left unattended, it would rot and emit a foul odor, and its fibrous nature would make it difficult to compost it, making it difficult to dispose of it. Therefore, they are incinerated by pouring heavy oil on them,
Once dried, it was spread on farmland, but it had drawbacks such as high fuel costs and the fact that it accumulated on farmland without being decomposed. However, we focused on the fact that water hyacinth begins to rot if left unattended, so we allowed some of the water hyacinth to rot in a storage tank. This increases the concentration of organic matter in the juice and also makes it compatible with anaerobic fermentation. By squeezing with a press machine such as a roller press or a screw press, the separated waste becomes flat and has an increased surface area, and the roots in particular are shredded and become very easy to dry. It is difficult to aerobically ferment water hyacinth as it is, but it can be composted by drying it and mixing it with sludge etc. to adjust the moisture content to a range of 40 to 60%. The present invention focuses on this point and proposes a method for processing and reusing water hyacinth, which recovers effective digestive gas from water hyacinth, which is difficult to process, and composts the dehydrated residue.
That is, in the treatment of water hyacinth cultivated and collected for the purpose of purifying water bodies, the present invention temporarily stores the collected water hyacinth, allows it to partially rot, then presses it to separate solid and liquid, and uses the squeezed liquid to produce methane. The purpose is to recover digestive gas from water hyacinth and obtain high-quality compost by performing fermentation, mixing the separated residue with digested sludge discharged from a methane fermentation tank, performing aerobic fermentation, and composting. . The present invention will be explained below with reference to a flowchart of a water hyacinth treatment and recycling method shown in the drawings. Water hyacinth that is no longer needed is collected from ponds, rivers, lakes and marshes where water bodies are purified, etc., and from, for example, water hyacinth cultivation ponds, and is stored as is in a storage pit or the like for temporary storage. During this storage, the water hyacinth begins to rot due to microorganisms that adhere to the stems and roots of the water hyacinth. This water hyacinth is mostly fibrous as it is, and even if it is squeezed, the concentration of organic matter in the juice is low, but by storage, a high-concentration juice can be obtained, and at the same time it becomes a process of adaptation to anaerobic digestion. Next, this water hyacinth that has begun to rot is sent to a squeezing process such as a screw press or roller press.
Solid-liquid separation is performed here. For methane gas fermentation, it is necessary for the fermentation liquor to have good fluidity, and by separating solid and liquid in this squeezing step, a fermentation stock solution with high concentration and good properties can be obtained. On the other hand, water hyacinth has a high water content (95
%), and the volume of the stem part is large,
Because it contains a lot of water, it takes a long time to dry. However, changing the shape using a press increases the surface area, significantly shortens the drying period, and particularly shreds the roots, which are difficult to decompose. This solid-liquid separated solid, that is, separated waste, is sent to a drying process, and the squeezed liquid is sent to a methane fermentation tank and stored there, where methane gas, that is, digestion gas, is generated. It is used to heat the methane fermentation tank, and the digested sludge generated from the fermentation tank is dehydrated and used as a raw material for compost, and the fermentation waste liquid is returned to the water hyacinth cultivation area together with the sludge-removed water for purification and then released. The dehydrated cake of digested sludge is mixed with the dried separated sludge, the moisture content is adjusted to 40 to 60%, and the cake is sent to an aerobic fermentation tank where rapid aerobic fermentation is performed using forced ventilation. It is difficult to compost Oteia hyacinth alone, but it can be fermented if it is dried and mixed with sludge to bring the moisture content to a range of 40 to 60%. Water hyacinth treated in this way becomes compost and is used as an excellent soil conditioner. The fertilizer components consisting of water hyacinth and dehydrated sludge thus obtained are shown in the table below.

[Table] In general, compost made from sludge such as digested sludge has a sufficient amount of nitrogen and phosphorus but is low in potassium components, but because water hyacinth contains a large amount of potassium components, the resulting compost has a suitable N:P:K ratio. . According to the present invention, water hyacinth used for water purification is used as a material for both methane fermentation and aerobic fermentation, and is exchanged into useful resources such as digestive gas and compost, and at this time, the water hyacinth used for water purification is used as a material for both methane fermentation and aerobic fermentation. Digested sludge is used as raw material for composting, part of the digested gas is used to heat the methane fermentation tank, and the waste liquid is slightly heated and returned to the water hyacinth cultivation pond where it is purified and then released. However, at this time, the cultivation of water hyacinth is promoted by the heated waste liquid, and the present invention is a closed system without waste, and the water hyacinth used for water purification can be effectively used. Instead of incinerating it at the expense of fuel, it would be difficult to decompose and accumulate in the soil if it was dried and returned to farmland, which caused problems, but by composting it, it has the advantage of becoming an excellent soil conditioner. .

[Brief explanation of the drawing]

The drawing is a flowchart showing the method for processing and reusing water hyacinth according to the present invention.

Claims (1)

[Claims] 1 Water hyacinth is temporarily stored and partially rotted, then squeezed to separate solid and liquid, the juice is used for methane fermentation, and the separated residue is mixed with digested sludge discharged from the methane fermentation tank. A method for processing water hyacinth characterized by performing aerobic fermentation and composting.