Microplastics (MPs) pose a global environmental challenge due to their persistence and ability to accumulate and transport pollutants. This chapter discusses the MP sources and impacts in various environments. Wastewater treatment plants often serve as a sink for MPs. Nonetheless, MPs concentrate in sludge, where they undergo physical and chemical alterations during the treatment process. The physicochemical changes enhanced their binding capacity for other contaminants. Hence, improper sewage treatment can lead to the release of pollutant-bound MPs into the environment, posing significant risks to ecosystems and human health. This chapter explores MP behaviour, fate and impacts on sewage sludge treatment, including their influences on composting efficiency, microbial community and compost quality. To address the MP pollution, the potential of polyhydroxyalkanoates (PHAs) as green and sustainable alternatives to conventional plastics is discussed. PHAs exhibit superior characteristics with full biodegradability. Their versatility makes them promising candidates for various applications. However, knowledge gaps remain regarding degradable and non-degradable MP behaviour in sludge and their overall impacts on sewage sludge management. Comprehensive research is essential to develop effective and sustainable waste management strategies for mitigating MP pollution.