Water, Wastewater, Waste Management in Agriculture and Agri-Food Industry

1. Introduction

Attaining sustainable development is one of the most important challenges of the 21st century. However, society’s impact on the environment is becoming increasingly evident; this is an issue that concerns almost every country in the world. Despite the development of newer technologies, many people still do not have access to adequate resources, including (but not limited to) food and water. With circular economy becoming a globally acknowledged philosophy, water, food, and other resources should be protected both qualitatively and quantitatively.

Water is the most valuable resource on Earth. It is necessary for the survival of living organisms and the functioning of the biosphere. Every person on our planet should have access to clean water, but according to some estimates, up to 1–2 billion people live in areas where access to drinking water is limited. The lack of water, poor water quality, and problems with sanitary infrastructure may affect how well people function and impact food security. There is enough water on Earth, but due to imbalances, inadequate management, the lack of education, and other problems, millions of people are dying. According to Wu et al. [1], droughts present substantial challenges to agriculture, food security, and water resources. Importantly, droughts primarily affect the poorest regions of the world, which only increases hunger and problems in these areas.

The Sustainable Development Goals (SDGs) were adopted by the United Nations in 2015 to work toward a sustainable and poverty-free world by 2030. Goal 6 concerns the issue of granting people access to clean water and providing adequate sanitation services worldwide. Numerous scientific studies discuss this topic, including Wisser et al.’s [2], in which the authors describe spatially varying global assessments of water consumption and withdrawal from livestock agri-food systems.

Wastewater management is directly related to water management. Wastewater consists primarily of used water and various solid, liquid, and gaseous pollutants that should be removed during the treatment process. Extremely important microbiological contaminants also play a crucial role. In recent years, research on the presence of antibiotics and microplastics in sewage has become particularly important. The first issue regarding antibiotics was discussed by, among others, Samrot et al. [3] in their paper “Sources of Antibiotic Contamination in Wastewater and Approaches to Their Removal—An Overview”. The second aspect concerning microplastics was presented in the paper “Microplastics in Wastewater and Drinking Water Treatment Plants: Occurrence and Removal of Microfibres” by Sol et al. [4].

Wastewater treatment is one of the elements of water protection. For this reason, scientific research on this topic should be systematically conducted. Soares [5], in their paper “Wastewater treatment in 2050: Challenges ahead and future vision in a European context”, emphasized that next-generation technologies will be influenced by the need to reduce carbon emissions combined with rigorous regulations whilst promoting water re-use.

According to Czekała et al. [6], an interesting substrate that can be used in biogas production is bio-waste from the municipal sector. One of the directions of using bio-waste is its use with sewage sludge in anaerobic digestion processes. In this case, the municipal sector dealing with waste management and water and sewage management may benefit.

The Special Issue titled “Water, Wastewater, Waste Management in Agriculture and Agri-Food Industry” covered topics related to sustainable water, sewage, and waste management, including resource reduction, treatment, and environmental impact.

2. Overview of the Special Issue

The papers collected in the Special Issue were diverse. The ten papers included were grouped by the Special Issue’s Editors into four categories:

(1)

Water management and water quality:

• Variability in the Chemical Composition of Spring Waters in the Postomia River Catchment (Northwest Poland) (Contribution 1).
• The Impact of Land Cover on Selected Water Quality Parameters in Polish Lowland Streams during the Non-Vegetative Period (Contribution 2).
• Changes in the Ecological Status of Rivers Caused by the Functioning of Natural Barriers (Contribution 3).
• Changes in the Amount of Rainwater in the Roztocze National Park (Poland) in 2001–2020 and the Possibility of Using Rainwater in the Context of Ongoing Climate Variability (Contribution 4).
• The Importance of Groundwater Quality and Other Habitat Parameters for Effective Active Protection of an Endangered Plant Species in Eastern Poland (Contribution 5).

(2)

Wastewater management:

• Sustainable vs. Conventional Approach for Olive Oil Wastewater Management: A Review of the State of the Art (Contribution 6).

(3)

Fertilizers:

• Water Disappearance and Manure Production at Growing–Finishing Commercial Pig Farms in Brazil—A Simplified Model Approach (Contribution 7).
• Sequential Analysis of Phosphorus Compounds Contained in the Substrates and the Digestate (Contribution 8).
• Digestate as a Source of Nutrients: Nitrogen and Its Fractions (Contribution 9).

(4)

Irrigation:

• Laboratory Tests of Water Level Regulators in Ditches of Irrigation Systems (Contribution 10).

The paper “Variability in the Chemical Composition of Spring Waters in the Postomia River Catchment (Northwest Poland)” by Siepak et al. (Contribution 1) presents the results of physicochemical analyzes of spring waters in the Postomia River valley (Northwest Poland). The physicochemical status of the spring waters was determined based on 51 parameters. As indicated by the authors, conducting a component analysis did not permit the identification of a single dominant origin with regard to most of the studied elements, suggesting the interaction of different pollution sources.

Łaszewski et al. (Contribution 2) in the paper “The Impact of Land Cover on Selected Water Quality Parameters in Polish Lowland Streams during the Non-Vegetative Period” investigated relationships between land cover indices and selected water quality parameters based on the example of 54 lowland temperate streams located in central Poland. The study provided a spatially extensive insight into the impact of land cover predictors at different scales on nitrogen compounds in a lowland landscape.

In the paper “Changes in the Ecological Status of Rivers Caused by the Functioning of Natural Barriers” written by Połeć et al. (Contribution 3), the hydromorphological state in terms of the diversification of land use and the conditions of the protected species significantly affecting the transformation of the river bed morphology and water conditions were discussed. As indicated by the authors, this research study confirmed the significant influence of the European beaver on changes in the environment.

The paper “Changes in the Amount of Rainwater in the Roztocze National Park (Poland) in 2001–2020 and the Possibility of Using Rainwater in the Context of Ongoing Climate Variability” presents data on changes in the amount of rainwater in the Roztocze National Park (Poland). The authors discuss the possibilities of using rainwater for various purposes in the context of climate change, which is taking place in this protected area (Contribution 4).

Serafin et al. (Contribution 5), in their paper “The Importance of Groundwater Quality and Other Habitat Parameters for Effective Active Protection of an Endangered Plant Species in Eastern Poland”, verify whether the sites chosen for the reintroduction of the endangered species Salix lapponum had been well selected by analyzing selected habitat parameters. Verifying and determining changes in their values may, in the long term, have a significant impact on the functioning of new populations of the species.

In the paper “Sustainable vs. Conventional Approach for Olive Oil Wastewater Management: A Review of the State of the Art” prepared by Al-Qodah et al. (Contribution 6), recently published research studies concerning the conventional and sustainable treatment processes for olive mill wastewater were collected and analyzed. According to the authors, more research could be conducted to obtain polyphenols and other valuable compounds from olive leaves. Consisting of 44 pages and containing 286 references, this paper constitutes a thorough and extensive piece of research.

The paper “Water Disappearance and Manure Production at Growing–Finishing Commercial Pig Farms in Brazil—A Simplified Model Approach” written by Tavares et al. (Contribution 7) concerns fitting water disappearance and manure production curves at growing–finishing commercial pig farms and comparing them with the curves that best describe the evolution of parameters based on three variables: age, body weight, and pigs’ housing period.

Wiater, in their paper “Sequential Analysis of Phosphorus Compounds Contained in the Substrates and the Digestate” (Contribution 8), determined the properties of the components used for fermentation feedstock and digestate. The content of phosphorus (and its proportion) was determined in fermentation feedstock in a real-scale agricultural biogas plant and in digestate. One of the paper’s conclusions indicated that the percentage of bioavailable phosphorus in fermentation feedstock was about 60% in relation to the total phosphorus content.

In their paper “Digestate as a Source of Nutrients: Nitrogen and Its Fractions” (Contribution 9), Czekała determined the content of total nitrogen (Ntot) and its selected fractions in raw and processed digestate from agricultural biogas plants. The obtained results showed that the digestate from agricultural biogas plants was a nitrogen-rich fertilizer. The content of Ntot in the tested samples ranged from 1.63 g∙kg⁻¹ to 13.22 g∙kg⁻¹ FM. The N-NH4 content in the analyzed material ranged from 0.75 to 4.75 g∙kg⁻¹ FM.

In the paper “Laboratory Tests of Water Level Regulators in Ditches of Irrigation Systems”, laboratory research was conducted to determine the hydraulic characteristics and operating conditions of three innovative regulator solutions. As indicated by the authors, the tested regulators were suitable for damming water in ditches at flows equal to and greater than the effective flow, that is, equal to water losses caused by leakages (Contribution 10).

3. Conclusions

This Special Issue presented various contributions covering specific areas of research pertaining to water, wastewater, and waste management. The topics covered in this Special Issue were very diverse due to its broad scope. The published papers showed how important considerations of water, wastewater, and waste management are in the context of agriculture as well as the agri-food industry. The Special Issue’s Guest Editors would like to thank all of the authors involved in this Special Issue and invite for further scientific activity in this area.