Recycled Water

What disgusts can turn into what fertilizes. 

SULLANA, Peru - While many people continue to see the residual water of the hydrobiological industry, disgusted and annoyed, quite few assume it as the raw material for obtaining an organic fertilizer without toxicity, with a high benefit for the crops where it is applied, plus can recuperate agriculturally overexploited soils or fertilizing  the ones with possibilities to enlarge the agricultural frontier.

The discomfort is presented among the people and some authorities because the industry continues to use the urban sewerage for undoing the called effluents or residual water gotten after the whole process, so the Chira River continues to be polluted despite a treatment plant still postponing while bureaucratic details are adjusted between the Peruvian government and the municipal administration of Sullana Province.

Until then, one solution is not pouring the effluents into the sewerage but bringing them to Gestión y Manejo de Residuos Sólidos (GEMA-RS) plant, located near Sullana-Piura Highway, that started to operate in 2015-ending after many bureaucratic locks, transforming the organic residues of the city into compost, setting up as a goal reducing the contamination of Chira River 80% around.

Since that experience until now, GEMA-RS has added the production of biol, an organic fertilizer that uses the effluents from Sullana City-based hydrobiological industry  as its raw material.

It is considered an effluent all residual water which quality has been negatively affected by any human commercial and industrial activity, what needs a new physical-chemical or biological process that purifies as much as possible when is impossible to re-use in its actual stage. One of those ways is by resuming it to a anaerobic digestion, or extraction of nutrients in absence of oxygen, what is precisely  the principle of biol obtaining.

The biol is the result of dung-&-water fermentation through the chemical decomposition and transformation of organic residues in an anaerobic environment. The technique is through biodigesters. Once used in the soil as fertilizer, it allows a better development of the plants, increasing their productiveness.

And nitrogen (N) is the key of everything, the gas forming a great proportion of the terrestrial atmosphere,  one of the life components in our planet with the carbon (C), the hydrogen (H) and the oxygen (O).

Enriched And Odorless
The biol obtained from residual water presents a major quantity of macronutrients -nitrogen (N), phosphorun (P),  and potasium (K)- in its composition than the obtained one from  well water. But, not all the industrial effluents are rich in nitrogen, phosphorun neither, for the microbial communities to develop the necessary activity that biologically depures. That is why you need to add both elements for recovering its action power.

In those cases, problems can be presented as growth of non-wanted bacteria, excess of extracellular polymers production, mud hydrolisis, major starting-up time and less production of gases in the anaerobic systems, emissions of nutrients in the recipient, non-wanted biological growth, major production of mud. Also, one of the disadvantages producing this substance is the detachment of stench due to the hydrogen sulphide (H₂S), that is naturally found in all residual waters.

There are many ways to fight the stench this gas produces, from those only masking it to  those completely mitigating it, like the use of efficient microorganisms, EM, a natural procedure that  has begun to extend the last years. In fact, when choosing to use EM adeqquatly, the product outputting  from the biodigestor does not absolutely smell, attract insects neither. This is precisely the procedure GEMA-RS uses for obtaining biol.

Once obtained, it is poured in a 50-cubic-meter or 13209-gallon pond containing residual water of hydro-biological which a mixed material was previously applied. Constant aeration is made to this system with a Venturi aerator.

Due to its great organic composition, the biol also can be used to enrich the production of compost, raising the quantity of nutrients as carbon and nitrogen, as well as the quantity and variety of microorganisms in charge of the composting material's degradation, increasing the metabolic rate of them, accelerating  the speed of compostage process.

FACTORTIERRA: Unpunished stench

Photos by John Leonardo Flores/FACTORTIERRA 

BASIC TECHNICAL INFORMATION ON BIOL

Benefits

• Allows a major conservation of nitrogen, so helps to structure soils in a natural way. As a result, it can raise the productiveness of crops installed there.
• Its fertilization capability of the soil is greater than fresh dung or composted dung, because it guarantees better  the conversion of nitrogen into ammonium (NH₄+).
• Being an improver of the soil's nutrients availability, , it raises its hydric availability, creating an adequate micro-climate for the plants due to its content of fitoregulators, what control the physiological processes, stimulate the formation of new roots, induct  the flowering, have fruitful action.
• Generates major vegetal material.
• The production can raise in a 30% to 50% range, that adds its totally organic character, what guarantees harmlessness, only even there is no direct or indirect influence of other agricultural products.
• Allows to obtain a compost  with excellent properties capable to promote physiological activities and stimulate the development of the plants, favoring its rooting, elapsing the leaf growth phase (what will charge photosynthesis), improving the flowering, and activating the germinative potence and power of the seeds.

Factors Influencing Into the Biol's Development

Temperature
The temperature of operation is one of the main parameters to consider, because abrupt variations can provocate a destabilization  of fermentation process. Those variations cause a declination of microbial metabolism due to degradation of enzymes, what agravates the life of cells.

The process temperature also influences in other physical-chemical parameters of the anaerobic digestion, like the solubility and the viscosity.

• The solubility of the generated gases falls down  when the temperature raises, favoring the liquid-gas transference. This could diminish the concentration of toxic gases, like ammonia (NH₃) and hydrogen sulphide (H₂S), benefitting the growth of anaerobic bacteria.
• The decline of carbon dioxide (CO₂) solubility could provocate an increasing of the pH, what ccould generate high-concentration ammonium (NH₄+) muds, producing possible inhibitions of ammonia (NH₃).
• The solubility of the most salt raises with the temperature, what eases the access of organic matter to the bacteries, accelerating the process.
• The viscosity of solids and semisolids falls down when the temperature raises, what implies less need to shake.

pH And Alkalinity
The range of anaerobic digestion's optimal pH  is 6,5 to 7,5. That is why the process pH must not be out of that range for developing satisfactorily. The increasing or diminishing of pH can inhibit the fermentation or stopping it.

Time Of Retention
The time of retention is the number of days those certain quantity of residual scrap or water must keep inside the biodigester, for the bacterial groups to degrade the organic matter because its metabolic activity.

The time of retention  is related to two type of factors: the type of substratum, an its temperature.

• A major temperature origins a diminishing in times of retention for fermentation, then consequently  the volumes of the reactor needed for the digestion of a determined volume of substratum will be minor.
• About the type of substratum, the components with a major proportion of retained carbon (cellulose) used in the process require major times of retention to be totally degraded.

Carbon/Nitrogen Relation
Among all elements  and nutrients conforming the organic matter, the carbon (C) and the nitrogen (N) are the main sources of the feeding for methane-forming bacteria (CH₄). The carbon is the source of energy while the nitrogen stimulates the formation of new cells and the bacterial growth.

The nitrogen contained in the digestion presents double benefit: it serves for  synthesis of aminoacids, proteins and nucleic acids of bacteria, and is transformed into ammonia, compound that holds the pH neutrality. An excess of nitrogen produces an excessive formation of ammonia, what is toxic for some bacteries and inhibits the process, and an insufficient quantity of nytrogen limits the reproduction of microorganisms.

The mycroorganisms must consume the carbon and the nytrogen (main nutrients) into a determined proportion, and this value is measured by the carbon/nytrogen (C/N) relation contained by the organic matter used in the operation.

The general criterion is that the quantitty of carbon related to the quantity of nytrogen (C/N( in the organic material  to degrade must be  a relation of 20 to 30.

C/N values less than 20:1 for fermentation are inhibitory because it causes an excessive formation of ammonia, while values over 30:1 denote the scarse of nytrogen, what causes a decreasing in  the growth of bacterial adds. Then, the values of C/N tables allow to combine different substrata (animal, vegetal origin, etc) for obtaining a global an optimal C/N for digestion, considering the experimentation environmental conditions.

Agitation
In anaerobic digestion, a good mix of substrata conforming the inner of the biodigester is important for the process development. The objectives of biodigester content's agitation are following:

• To holdan uniform temperature across the whole anaerobic reactor.
• To avoid the formation of foams and the sedimentation in the biodigester content.
• To generate the contact of the fresh substratum with the bacterial groups.
• To avoid the creation of dead spaces without biological activity, those can reduce the effective volume of the reactor.
• To remove the metabolites produced by the methanogenic bacteries.

Toxicity And Inhibitors
The process of anaerobic digestion inhibits and disminishes the speed of biogas production in presence of toxic substances in the system. Those substances can be 116, like:

• Intermediate bi-products or products  of the metabolic activity, the anaerobic organisms of the reactor: hydrogen, hydrogen sulphide, ammonia, volatile fat acids (VFA).
• Substances forming the substratum.
• Substances bursting into the system, accidentally or other causes.

Content Of Solids
Every organic matter is composed by water and a solid fraction, called total solids. Inside the anaerobic reactor, as much as it increases the content of solids, the mobility of methanogenic bacteria inside the substratum  sees limited, so the production of biogas decreases. That is why  the content solids value must be limited for avoiding unbalance in the digestion process.

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